Merge branch 'mb/diogenes' into develop

31 files changed, 959 insertions, 779 deletions

diff --git a/test/apps/schema-1.nt b/test/apps/schema-1.nt
index e57146d..4daf0ad 100644
--- a/test/apps/schema-1.nt
+++ b/test/apps/schema-1.nt
@@ -3,8 +3,8 @@ prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
 prefix xsd: <http://www.w3.org/2001/XMLSchema#>
 
 # common bsfs prefixes
-prefix bsfs: <http://bsfs.ai/schema/>
-prefix bse: <http://bsfs.ai/schema/Entity#>
+prefix bsfs: <http://schema.bsfs.io/core/>
+prefix bse: <http://schema.bsfs.io/core/Node/Entity#>
 
 # essential nodes
 bsfs:Entity rdfs:subClassOf bsfs:Node .
diff --git a/test/apps/schema-2.nt b/test/apps/schema-2.nt
index 4c5468f..4eb2467 100644
--- a/test/apps/schema-2.nt
+++ b/test/apps/schema-2.nt
@@ -3,8 +3,8 @@ prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
 prefix xsd: <http://www.w3.org/2001/XMLSchema#>
 
 # common bsfs prefixes
-prefix bsfs: <http://bsfs.ai/schema/>
-prefix bse: <http://bsfs.ai/schema/Entity#>
+prefix bsfs: <http://schema.bsfs.io/core/>
+prefix bse: <http://schema.bsfs.io/core/Node/Entity#>
 
 # essential nodes
 bsfs:Entity rdfs:subClassOf bsfs:Node .
diff --git a/test/apps/test_init.py b/test/apps/test_init.py
index bae6a68..59e10eb 100644
--- a/test/apps/test_init.py
+++ b/test/apps/test_init.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import contextlib
 import io
diff --git a/test/apps/test_main.py b/test/apps/test_main.py
new file mode 100644
index 0000000..d61372f
--- /dev/null
+++ b/test/apps/test_main.py
@@ -0,0 +1,37 @@
+
+# imports
+import contextlib
+import io
+import json
+import unittest
+
+# objects to test
+from bsfs.apps import main
+
+
+## code ##
+
+class TestMain(unittest.TestCase):
+    def test_main(self):
+        # must at least pass an app
+        with contextlib.redirect_stderr(io.StringIO()):
+            self.assertRaises(SystemExit, main, [])
+        # app takes over
+        with contextlib.redirect_stderr(io.StringIO()):
+            self.assertRaises(SystemExit, main, ['init'])
+        outbuf = io.StringIO()
+        with contextlib.redirect_stdout(outbuf):
+            main(['init', 'sparql'])
+        self.assertEqual(json.loads(outbuf.getvalue()), {
+            'Graph': {
+                'user': 'http://example.com/me',
+                'backend': {
+                    'SparqlStore': {}}}})
+
+
+## main ##
+
+if __name__ == '__main__':
+    unittest.main()
+
+## EOF ##
diff --git a/test/apps/test_migrate.py b/test/apps/test_migrate.py
index 230c032..618cb37 100644
--- a/test/apps/test_migrate.py
+++ b/test/apps/test_migrate.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import contextlib
 import io
diff --git a/test/front/test_bsfs.py b/test/front/test_bsfs.py
index 0d7f383..8905bf8 100644
--- a/test/front/test_bsfs.py
+++ b/test/front/test_bsfs.py
@@ -1,14 +1,10 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import unittest
 
 # bsie imports
 from bsfs.graph import Graph
+from bsfs.graph.ac import NullAC
 from bsfs.triple_store import SparqlStore
 from bsfs.utils import errors, URI
 
@@ -25,7 +21,7 @@ class TestBSFS(unittest.TestCase):
         graph = Open(config)
         self.assertIsInstance(graph, Graph)
         self.assertIsInstance(graph._backend, SparqlStore)
-        self.assertEqual(graph._user, URI('http://example.com/me'))
+        self.assertEqual(graph._ac, NullAC(graph._backend, URI('http://example.com/me')))
         # invalid config raises an error
         self.assertRaises(errors.ConfigError, Open, {})
 
diff --git a/test/front/test_builder.py b/test/front/test_builder.py
index 08f2027..875fa8a 100644
--- a/test/front/test_builder.py
+++ b/test/front/test_builder.py
@@ -1,14 +1,10 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import unittest
 
 # bsie imports
 from bsfs.graph import Graph
+from bsfs.graph.ac import NullAC
 from bsfs.triple_store import SparqlStore
 from bsfs.utils import errors, URI
 
@@ -40,7 +36,7 @@ class TestBuilder(unittest.TestCase):
         graph = build_graph({'Graph': {'backend': {'SparqlStore': {}}, 'user': 'http://example.com/me'}})
         self.assertIsInstance(graph, Graph)
         self.assertIsInstance(graph._backend, SparqlStore)
-        self.assertEqual(graph._user, URI('http://example.com/me'))
+        self.assertEqual(graph._ac, NullAC(graph._backend, URI('http://example.com/me')))
         # cannot create an invalid graph
         self.assertRaises(errors.ConfigError, build_graph, {'MyGraph': {}})
         # must pass a dict
diff --git a/test/graph/ac/test_base.py b/test/graph/ac/test_base.py
new file mode 100644
index 0000000..addecd4
--- /dev/null
+++ b/test/graph/ac/test_base.py
@@ -0,0 +1,78 @@
+
+# imports
+import unittest
+
+# bsie imports
+from bsfs import schema as bsc
+from bsfs.namespace import ns
+from bsfs.query import ast
+from bsfs.triple_store import SparqlStore
+from bsfs.utils import URI
+
+# objects to test
+from bsfs.graph.ac.base import AccessControlBase
+
+
+## code ##
+
+class StubAC(AccessControlBase):
+    def is_protected_predicate(self, pred):
+        pass
+    def create(self, node_type, guids):
+        pass
+    def link_from_node(self, node_type, guids):
+        pass
+    def link_to_node(self, node_type, guids):
+        pass
+    def write_literal(self, node_type, guids):
+        pass
+    def createable(self, node_type, guids):
+        pass
+    def filter_read(self, node_type, query):
+        pass
+    def fetch_read(self, node_type, query):
+        pass
+
+
+class TestAccessControlBase(unittest.TestCase):
+    def setUp(self):
+        self.backend = SparqlStore()
+        self.user = URI('http://www.example.com/me')
+
+    def test_essentials(self):
+        ac = StubAC(self.backend, self.user)
+        # equal construction means equal instance
+        self.assertEqual(StubAC(self.backend, self.user), StubAC(self.backend, self.user))
+        self.assertEqual(hash(StubAC(self.backend, self.user)), hash(StubAC(self.backend, self.user)))
+        self.assertEqual(ac, StubAC(self.backend, self.user))
+        self.assertEqual(hash(ac), hash(StubAC(self.backend, self.user)))
+        # equivalence respects type
+        class Foo(): pass
+        self.assertNotEqual(ac, 1234)
+        self.assertNotEqual(hash(ac), hash(1234))
+        self.assertNotEqual(ac, 'hello')
+        self.assertNotEqual(hash(ac), hash('hello'))
+        self.assertNotEqual(ac, Foo())
+        self.assertNotEqual(hash(ac), hash(Foo()))
+        # equivalence respects backend
+        self.assertNotEqual(ac, StubAC(SparqlStore(), self.user))
+        self.assertNotEqual(hash(ac), hash(StubAC(SparqlStore(), self.user)))
+        # equivalence respects user
+        self.assertNotEqual(ac, StubAC(self.backend, URI('http://www.example.com/you')))
+        self.assertNotEqual(hash(ac), hash(StubAC(self.backend, URI('http://www.example.com/you'))))
+        # string conversion
+        self.assertEqual(str(ac), f'StubAC({self.user})')
+        self.assertEqual(repr(ac), f'StubAC({self.user})')
+        # string conversion respects user
+        self.assertEqual(str(StubAC(self.backend, URI('http://www.example.com/you'))),
+            f'StubAC(http://www.example.com/you)')
+        self.assertEqual(repr(StubAC(self.backend, URI('http://www.example.com/you'))),
+            f'StubAC(http://www.example.com/you)')
+
+
+## main ##
+
+if __name__ == '__main__':
+    unittest.main()
+
+## EOF ##
diff --git a/test/graph/ac/test_null.py b/test/graph/ac/test_null.py
index e35852d..142bc23 100644
--- a/test/graph/ac/test_null.py
+++ b/test/graph/ac/test_null.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import unittest
 
@@ -20,6 +15,8 @@ from bsfs.graph.ac.null import NullAC
 
 ## code ##
 
+ns.bse = ns.bsfs.Entity()
+
 class TestNullAC(unittest.TestCase):
     def setUp(self):
         self.backend = SparqlStore()
@@ -27,18 +24,19 @@ class TestNullAC(unittest.TestCase):
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
 
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bsm: <http://bsfs.ai/schema/Meta#>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsn: <https://schema.bsfs.io/core/Node#>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Tag rdfs:subClassOf bsfs:Node .
             xsd:string rdfs:subClassOf bsfs:Literal .
-            bsfs:Number rdfs:subClassOf bsfs:Literal .
-            xsd:integer rdfs:subClassOf bsfs:Number .
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsl:Number .
 
             # predicates mandated by Nodes
-            bsm:t_created rdfs:subClassOf bsfs:Predicate ;
+            bsn:t_created rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Node ;
                 rdfs:range xsd:integer ;
                 bsfs:unique "true"^^xsd:boolean .
@@ -64,10 +62,40 @@ class TestNullAC(unittest.TestCase):
         self.p_author = self.backend.schema.predicate(ns.bse.author)
         self.p_filesize = self.backend.schema.predicate(ns.bse.filesize)
         self.p_tag = self.backend.schema.predicate(ns.bse.tag)
-        self.p_created = self.backend.schema.predicate(ns.bsm.t_created)
+        self.p_created = self.backend.schema.predicate(ns.bsn.t_created)
         self.ent_type = self.backend.schema.node(ns.bsfs.Entity)
         self.ent_ids = {URI('http://www.example.com/me/entity#1234'), URI('http://www.example.com/me/entity#4321')}
 
+    def test_essentials(self):
+        ac = NullAC(self.backend, self.user)
+        # equal construction means equal instance
+        self.assertEqual(NullAC(self.backend, self.user), NullAC(self.backend, self.user))
+        self.assertEqual(hash(NullAC(self.backend, self.user)), hash(NullAC(self.backend, self.user)))
+        self.assertEqual(ac, NullAC(self.backend, self.user))
+        self.assertEqual(hash(ac), hash(NullAC(self.backend, self.user)))
+        # equivalence respects type
+        class Foo(): pass
+        self.assertNotEqual(ac, 1234)
+        self.assertNotEqual(hash(ac), hash(1234))
+        self.assertNotEqual(ac, 'hello')
+        self.assertNotEqual(hash(ac), hash('hello'))
+        self.assertNotEqual(ac, Foo())
+        self.assertNotEqual(hash(ac), hash(Foo()))
+        # equivalence respects backend
+        self.assertNotEqual(ac, NullAC(SparqlStore(), self.user))
+        self.assertNotEqual(hash(ac), hash(NullAC(SparqlStore(), self.user)))
+        # equivalence respects user
+        self.assertNotEqual(ac, NullAC(self.backend, URI('http://www.example.com/you')))
+        self.assertNotEqual(hash(ac), hash(NullAC(self.backend, URI('http://www.example.com/you'))))
+        # string conversion
+        self.assertEqual(str(ac), f'NullAC({self.user})')
+        self.assertEqual(repr(ac), f'NullAC({self.user})')
+        # string conversion respects user
+        self.assertEqual(str(NullAC(self.backend, URI('http://www.example.com/you'))),
+            f'NullAC(http://www.example.com/you)')
+        self.assertEqual(repr(NullAC(self.backend, URI('http://www.example.com/you'))),
+            f'NullAC(http://www.example.com/you)')
+
     def test_is_protected_predicate(self):
         ac = NullAC(self.backend, self.user)
         self.assertTrue(ac.is_protected_predicate(self.p_created))
@@ -101,8 +129,19 @@ class TestNullAC(unittest.TestCase):
             ast.filter.Any(ns.bse.tag, ast.filter.Is('http://example.com/tag#4321')),
             ast.filter.Any(ns.bse.author, ast.filter.Equals('Me, Myself, and I')))
         ac = NullAC(self.backend, self.user)
+        # NullAC returns query
         self.assertEqual(query, ac.filter_read(self.ent_type, query))
-        return query
+        # query can be none
+        self.assertIsNone(ac.filter_read(self.ent_type, None))
+
+    def test_fetch_read(self):
+        query = ast.fetch.All(
+            ast.fetch.Fetch(ns.bse.tag, ast.fetch.Value(ns.bse.label, 'tag_label')),
+            ast.fetch.Node(ns.bse.tag, 'tag_node'),
+            ast.fetch.Value(ns.bse.iso, 'iso'))
+        ac = NullAC(self.backend, self.user)
+        # NullAC returns query
+        self.assertEqual(query, ac.fetch_read(self.ent_type, query))
 
 
 ## main ##
diff --git a/test/graph/test_graph.py b/test/graph/test_graph.py
index 5db1fd2..167168d 100644
--- a/test/graph/test_graph.py
+++ b/test/graph/test_graph.py
@@ -1,14 +1,12 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
+from functools import reduce
+import operator
 import unittest
 
 # bsie imports
 from bsfs import schema
+from bsfs.graph.ac import NullAC
 from bsfs.graph.nodes import Nodes
 from bsfs.namespace import ns
 from bsfs.query import ast
@@ -21,96 +19,95 @@ from bsfs.graph.graph import Graph
 
 ## code ##
 
+ns.bse = ns.bsfs.Entity()
+
 class TestGraph(unittest.TestCase):
     def setUp(self):
-        self.user = URI('http://example.com/me')
         self.backend = SparqlStore.Open()
         self.backend.schema = schema.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bsfs: <https://schema.bsfs.io/core/>
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             ''')
+        self.user = URI('http://example.com/me')
+        self.ac = NullAC(self.backend, self.user)
 
     def test_str(self):
-        self.assertEqual(str(Graph(self.backend, self.user)),
-            'Graph(SparqlStore(uri=None), http://example.com/me)')
-        self.assertEqual(repr(Graph(self.backend, self.user)),
-            'Graph(backend=SparqlStore(uri=None), user=http://example.com/me)')
+        self.assertEqual(str(Graph(self.backend, self.ac)),
+            'Graph(SparqlStore(uri=None))')
+        self.assertEqual(repr(Graph(self.backend, self.ac)),
+            'Graph(SparqlStore(uri=None), NullAC(http://example.com/me))')
         # str respects backend
         class Foo(SparqlStore): pass
-        self.assertEqual(str(Graph(Foo.Open(), self.user)),
-            'Graph(Foo(uri=None), http://example.com/me)')
-        self.assertEqual(repr(Graph(Foo.Open(), self.user)),
-            'Graph(backend=Foo(uri=None), user=http://example.com/me)')
+        self.assertEqual(str(Graph(Foo.Open(), self.ac)),
+            'Graph(Foo(uri=None))')
+        self.assertEqual(repr(Graph(Foo.Open(), self.ac)),
+            'Graph(Foo(uri=None), NullAC(http://example.com/me))')
         # str respect user
-        self.assertEqual(str(Graph(self.backend, URI('http://example.com/you'))),
-            'Graph(SparqlStore(uri=None), http://example.com/you)')
-        self.assertEqual(repr(Graph(self.backend, URI('http://example.com/you'))),
-            'Graph(backend=SparqlStore(uri=None), user=http://example.com/you)')
+        self.assertEqual(str(Graph(self.backend, NullAC(self.backend, URI('http://example.com/you')))),
+            'Graph(SparqlStore(uri=None))')
+        self.assertEqual(repr(Graph(self.backend, NullAC(self.backend, URI('http://example.com/you')))),
+            'Graph(SparqlStore(uri=None), NullAC(http://example.com/you))')
         # str respects type
         class Bar(Graph): pass
-        self.assertEqual(str(Bar(self.backend, self.user)),
-            'Bar(SparqlStore(uri=None), http://example.com/me)')
-        self.assertEqual(repr(Bar(self.backend, self.user)),
-            'Bar(backend=SparqlStore(uri=None), user=http://example.com/me)')
+        self.assertEqual(str(Bar(self.backend, self.ac)),
+            'Bar(SparqlStore(uri=None))')
+        self.assertEqual(repr(Bar(self.backend, self.ac)),
+            'Bar(SparqlStore(uri=None), NullAC(http://example.com/me))')
 
     def test_equality(self):
-        graph = Graph(self.backend, self.user)
+        graph = Graph(self.backend, self.ac)
         # instance is equal to itself
         self.assertEqual(graph, graph)
         self.assertEqual(hash(graph), hash(graph))
         # instance is equal to a clone
-        self.assertEqual(graph, Graph(self.backend, self.user))
-        self.assertEqual(hash(graph), hash(Graph(self.backend, self.user)))
+        self.assertEqual(graph, Graph(self.backend, self.ac))
+        self.assertEqual(hash(graph), hash(Graph(self.backend, self.ac)))
         # equality respects backend
-        self.assertNotEqual(graph, Graph(SparqlStore.Open(), self.user))
-        self.assertNotEqual(hash(graph), hash(Graph(SparqlStore.Open(), self.user)))
+        self.assertNotEqual(graph, Graph(SparqlStore.Open(), self.ac))
+        self.assertNotEqual(hash(graph), hash(Graph(SparqlStore.Open(), self.ac)))
         # equality respects user
         self.assertNotEqual(graph, Graph(self.backend, URI('http://example.com/you')))
         self.assertNotEqual(hash(graph), hash(Graph(self.backend, URI('http://example.com/you'))))
 
     def test_essentials(self):
-        graph = Graph(self.backend, self.user)
+        graph = Graph(self.backend, self.ac)
         # schema
         self.assertEqual(graph.schema, self.backend.schema)
         self.assertRaises(AttributeError, setattr, graph, 'schema', None)
 
     def test_node(self):
-        graph = Graph(self.backend, self.user)
+        graph = Graph(self.backend, self.ac)
         guid = URI('http://example.com/me/entity#1234')
         # returns a Nodes instance
         self.assertEqual(
             graph.node(ns.bsfs.Entity, guid),
-            Nodes(self.backend, self.user, graph.schema.node(ns.bsfs.Entity), {guid}))
+            Nodes(self.backend, self.ac, graph.schema.node(ns.bsfs.Entity), {guid}))
         # node_type must be in the schema
         self.assertRaises(KeyError, graph.node, ns.bsfs.Invalid, guid)
 
     def test_nodes(self):
-        graph = Graph(self.backend, self.user)
+        graph = Graph(self.backend, self.ac)
         guids = {URI('http://example.com/me/entity#1234'), URI('http://example.com/me/entity#4321')}
         # returns a Nodes instance
         self.assertEqual(
             graph.nodes(ns.bsfs.Entity, guids),
-            Nodes(self.backend, self.user, graph.schema.node(ns.bsfs.Entity), guids))
+            Nodes(self.backend, self.ac, graph.schema.node(ns.bsfs.Entity), guids))
         # node_type must be in the schema
         self.assertRaises(KeyError, graph.nodes, ns.bsfs.Invalid, guids)
 
-    def test_all(self):
-        graph = Graph(self.backend, self.user)
-        # resulting nodes can be empty
-        self.assertEqual(graph.all(ns.bsfs.Entity),
-            Nodes(self.backend, self.user, graph.schema.node(ns.bsfs.Entity), set()))
-        # resulting nodes contains all nodes of the respective type
-        guids = {URI('http://example.com/me/entity#1234'), URI('http://example.com/me/entity#4321')}
-        self.backend.create(graph.schema.node(ns.bsfs.Entity), guids)
-        self.assertEqual(graph.all(ns.bsfs.Entity),
-            Nodes(self.backend, self.user, graph.schema.node(ns.bsfs.Entity), guids))
+    def test_empty(self):
+        graph = Graph(self.backend, self.ac)
+        # returns a Nodes instance
+        self.assertEqual(
+            graph.empty(ns.bsfs.Entity),
+            Nodes(self.backend, self.ac, graph.schema.node(ns.bsfs.Entity), set()))
         # node_type must be in the schema
-        self.assertRaises(KeyError, graph.all, ns.bsfs.Invalid)
+        self.assertRaises(KeyError, graph.empty, ns.bsfs.Invalid)
 
     def test_migrate(self):
         # setup
-        graph = Graph(self.backend, self.user)
+        graph = Graph(self.backend, self.ac)
 
         # argument must be a schema
         class Foo(): pass
@@ -134,12 +131,13 @@ class TestGraph(unittest.TestCase):
         target_1 = schema.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             xsd:string rdfs:subClassOf bsfs:Literal .
-            bsfs:Number rdfs:subClassOf bsfs:Literal .
-            xsd:integer rdfs:subClassOf bsfs:Number .
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsl:Number .
 
             bse:filename rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Entity ;
@@ -159,13 +157,14 @@ class TestGraph(unittest.TestCase):
         self.assertEqual(graph.schema, target_1 + schema.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bsm: <http://bsfs.ai/schema/Meta#>
-            bsfs:Number rdfs:subClassOf bsfs:Literal .
-            xsd:integer rdfs:subClassOf bsfs:Number .
-            bsm:t_created rdfs:subClassOf bsfs:Predicate ;
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bsn: <https://schema.bsfs.io/core/Node#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            xsd:float rdfs:subClassOf bsl:Number .
+            bsn:t_created rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Node ;
-                rdfs:range xsd:integer ;
+                rdfs:range xsd:float ;
                 bsfs:unique "true"^^xsd:boolean .
             '''))
 
@@ -173,12 +172,13 @@ class TestGraph(unittest.TestCase):
         target_2 = schema.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <http://schema.bsfs.io/core/>
+            prefix bse: <http://schema.bsfs.io/core/Node/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             xsd:string rdfs:subClassOf bsfs:Literal .
-            bsfs:Number rdfs:subClassOf bsfs:Literal .
-            xsd:integer rdfs:subClassOf bsfs:Number .
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsl:Number .
 
             bse:filename rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Entity ;
@@ -200,24 +200,25 @@ class TestGraph(unittest.TestCase):
         self.assertEqual(graph.schema, target_2 + schema.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bsm: <http://bsfs.ai/schema/Meta#>
-            bsfs:Number rdfs:subClassOf bsfs:Literal .
-            xsd:integer rdfs:subClassOf bsfs:Number .
-            bsm:t_created rdfs:subClassOf bsfs:Predicate ;
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bsn: <https://schema.bsfs.io/core/Node#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            xsd:float rdfs:subClassOf bsl:Number .
+            bsn:t_created rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Node ;
-                rdfs:range xsd:integer ;
+                rdfs:range xsd:float ;
                 bsfs:unique "true"^^xsd:boolean .
             '''))
 
     def test_get(self):
         # setup
-        graph = Graph(self.backend, self.user)
+        graph = Graph(self.backend, self.ac)
         graph.migrate(schema.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Tag rdfs:subClassOf bsfs:Node .
@@ -246,10 +247,10 @@ class TestGraph(unittest.TestCase):
         graph.node(ns.bsfs.Tag, URI('http://example.com/tag#1234')).set(ns.bse.comment, 'foo')
         graph.node(ns.bsfs.Tag, URI('http://example.com/tag#4321')).set(ns.bse.comment, 'bar')
 
-        # get exception for invalid query
+        # invalid query raises exception
         self.assertRaises(errors.ConsistencyError, graph.get, ns.bsfs.Entity, ast.filter.Any(ns.bse.tag, ast.filter.Equals('hello world')))
 
-        # query returns nodes
+        # get returns nodes
         self.assertEqual(graph.get(ns.bsfs.Entity, ast.filter.Any(ns.bse.tag, ast.filter.Is(tags))), ents)
         self.assertEqual(graph.get(ns.bsfs.Entity, ast.filter.Any(ns.bse.comment, ast.filter.StartsWith('foo'))),
             graph.node(ns.bsfs.Entity, URI('http://example.com/entity#1234')))
@@ -260,6 +261,81 @@ class TestGraph(unittest.TestCase):
             ast.filter.Any(ns.bse.tag, ast.filter.All(ns.bse.comment, ast.filter.Equals('bar'))))),
             ents)
 
+        # query can be None
+        self.assertEqual(graph.get(ns.bsfs.Entity, None), ents)
+
+    def test_sorted(self):
+        # setup
+        graph = Graph(self.backend, self.ac)
+        graph.migrate(schema.from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            bsfs:Tag rdfs:subClassOf bsfs:Node .
+            xsd:string rdfs:subClassOf bsfs:Literal .
+
+            bse:tag rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range bsfs:Tag ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            bse:comment rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Node ;
+                rdfs:range xsd:string ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            '''))
+        # add some instances
+        ents = [
+            # default is alphabetical order
+            graph.node(ns.bsfs.Entity, URI('http://example.com/entity#1234')),
+            graph.node(ns.bsfs.Entity, URI('http://example.com/entity#4321')),
+            ]
+        tags = graph.nodes(ns.bsfs.Tag, {URI('http://example.com/tag#1234'), URI('http://example.com/tag#4321')})
+        # add some node links
+        reduce(operator.add, ents).set(ns.bse.tag, tags)
+        # add some literals
+        graph.node(ns.bsfs.Entity, URI('http://example.com/entity#1234')).set(ns.bse.comment, 'hello world')
+        graph.node(ns.bsfs.Entity, URI('http://example.com/entity#1234')).set(ns.bse.comment, 'foo')
+        graph.node(ns.bsfs.Entity, URI('http://example.com/entity#1234')).set(ns.bse.comment, 'foobar')
+        graph.node(ns.bsfs.Tag, URI('http://example.com/tag#1234')).set(ns.bse.comment, 'foo')
+        graph.node(ns.bsfs.Tag, URI('http://example.com/tag#4321')).set(ns.bse.comment, 'bar')
+
+        # invalid query raises exception
+        self.assertRaises(errors.ConsistencyError, list, graph.sorted(ns.bsfs.Entity, ast.filter.Any(ns.bse.tag, ast.filter.Equals('hello world'))))
+
+        # get returns nodes
+        self.assertListEqual(list(graph.sorted(ns.bsfs.Entity, ast.filter.Any(ns.bse.tag, ast.filter.Is(tags)))), ents)
+        self.assertListEqual(list(graph.sorted(ns.bsfs.Entity, ast.filter.Any(ns.bse.comment, ast.filter.StartsWith('foo')))),
+            [graph.node(ns.bsfs.Entity, URI('http://example.com/entity#1234'))])
+        self.assertListEqual(list(graph.sorted(ns.bsfs.Node, ast.filter.Any(ns.bse.comment, ast.filter.StartsWith('foo')))), [
+            graph.node(ns.bsfs.Node, URI('http://example.com/entity#1234')),
+            graph.node(ns.bsfs.Node, URI('http://example.com/tag#1234')),
+            ])
+        self.assertListEqual(list(graph.sorted(ns.bsfs.Entity, ast.filter.Or(
+            ast.filter.Any(ns.bse.comment, ast.filter.EndsWith('bar')),
+            ast.filter.Any(ns.bse.tag, ast.filter.All(ns.bse.comment, ast.filter.Equals('bar')))))),
+            ents)
+
+        # query can be None
+        self.assertListEqual(list(graph.sorted(ns.bsfs.Entity, None)), ents)
+
+
+    def test_all(self):
+        graph = Graph(self.backend, self.ac)
+        # resulting nodes can be empty
+        self.assertEqual(graph.all(ns.bsfs.Entity),
+            Nodes(self.backend, self.ac, graph.schema.node(ns.bsfs.Entity), set()))
+        # resulting nodes contains all nodes of the respective type
+        guids = {URI('http://example.com/me/entity#1234'), URI('http://example.com/me/entity#4321')}
+        self.backend.create(graph.schema.node(ns.bsfs.Entity), guids)
+        self.assertEqual(graph.all(ns.bsfs.Entity),
+            Nodes(self.backend, self.ac, graph.schema.node(ns.bsfs.Entity), guids))
+        # node_type must be in the schema
+        self.assertRaises(KeyError, graph.all, ns.bsfs.Invalid)
 
 
 
diff --git a/test/graph/test_nodes.py b/test/graph/test_nodes.py
index 6bb3ef3..afe7522 100644
--- a/test/graph/test_nodes.py
+++ b/test/graph/test_nodes.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # standard imports
 from functools import partial
 import operator
@@ -14,6 +9,7 @@ import rdflib
 
 # bsie imports
 from bsfs import schema as bsc
+from bsfs.graph.ac import NullAC
 from bsfs.graph.walk import Walk
 from bsfs.namespace import Namespace, ns
 from bsfs.triple_store.sparql import SparqlStore
@@ -25,7 +21,8 @@ from bsfs.graph.nodes import Nodes
 
 ## code ##
 
-bst = Namespace('http://bsfs.ai/schema/Tag')
+ns.bse = ns.bsfs.Entity()
+ns.bst = ns.bsfs.Tag()
 
 class TestNodes(unittest.TestCase):
     def setUp(self):
@@ -35,20 +32,21 @@ class TestNodes(unittest.TestCase):
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
 
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bsm: <http://bsfs.ai/schema/Meta#>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
-            prefix bst: <http://bsfs.ai/schema/Tag#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsn: <https://schema.bsfs.io/core/Node#>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bst: <https://schema.bsfs.io/core/Tag#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Tag rdfs:subClassOf bsfs:Node .
             bsfs:User rdfs:subClassOf bsfs:Node .
             xsd:string rdfs:subClassOf bsfs:Literal .
-            bsfs:Number rdfs:subClassOf bsfs:Literal .
-            xsd:integer rdfs:subClassOf bsfs:Number .
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsl:Number .
 
             # predicates mandated by Nodes
-            bsm:t_created rdfs:subClassOf bsfs:Predicate ;
+            bsn:t_created rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Node ;
                 rdfs:range xsd:integer ;
                 bsfs:unique "true"^^xsd:boolean .
@@ -91,22 +89,23 @@ class TestNodes(unittest.TestCase):
             (rdflib.URIRef(ns.bsfs.Tag), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Node)),
             (rdflib.URIRef(ns.bsfs.User), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Node)),
             (rdflib.URIRef(ns.xsd.string), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.bsfs.Array), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.bsfs.BinaryBlob), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.bsfs.Feature), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Array)),
-            (rdflib.URIRef(ns.bsfs.Number), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.bsfs.Time), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.xsd.integer), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Number)),
-            (rdflib.URIRef(ns.bsm.t_created), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
+            (rdflib.URIRef(ns.bsl.Array), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
+            (rdflib.URIRef(ns.bsl.BinaryBlob), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
+            (rdflib.URIRef(ns.bsl.Array.Feature), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsl.Array)),
+            (rdflib.URIRef(ns.bsl.Number), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
+            (rdflib.URIRef(ns.bsl.Time), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
+            (rdflib.URIRef(ns.xsd.integer), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsl.Number)),
+            (rdflib.URIRef(ns.bsn.t_created), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             (rdflib.URIRef(ns.bse.comment), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             (rdflib.URIRef(ns.bse.filesize), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             (rdflib.URIRef(ns.bse.tag), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             (rdflib.URIRef(ns.bse.author), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
-            (rdflib.URIRef(bst.representative), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
-            (rdflib.URIRef(bst.label), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
+            (rdflib.URIRef(ns.bst.representative), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
+            (rdflib.URIRef(ns.bst.label), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             }
         # Nodes constructor args
         self.user = URI('http://example.com/me')
+        self.ac = NullAC(self.backend, self.user)
         # set args
         self.tag_type = self.backend.schema.node(ns.bsfs.Tag)
         self.ent_type = self.backend.schema.node(ns.bsfs.Entity)
@@ -114,9 +113,9 @@ class TestNodes(unittest.TestCase):
         self.p_filesize = self.backend.schema.predicate(ns.bse.filesize)
         self.p_author = self.backend.schema.predicate(ns.bse.author)
         self.p_tag = self.backend.schema.predicate(ns.bse.tag)
-        self.p_representative = self.backend.schema.predicate(bst.representative)
-        self.p_label = self.backend.schema.predicate(bst.label)
-        self.t_created = self.backend.schema.predicate(ns.bsm.t_created)
+        self.p_representative = self.backend.schema.predicate(ns.bst.representative)
+        self.p_label = self.backend.schema.predicate(ns.bst.label)
+        self.t_created = self.backend.schema.predicate(ns.bsn.t_created)
         self.ent_ids = {
             URI('http://example.com/me/entity#1234'),
             URI('http://example.com/me/entity#4321'),
@@ -126,67 +125,71 @@ class TestNodes(unittest.TestCase):
             URI('http://example.com/me/tag#4321'),
             }
 
+    def test_construct(self):
+        self.assertIsInstance(Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me-and-you'}), Nodes)
+        self.assertRaises(ValueError, Nodes, self.backend, self.ac, self.ent_type, {'http://example.com/me and you'})
+
     def test_str(self):
         # str baseline
-        nodes = Nodes(self.backend, self.user, self.ent_type, self.ent_ids)
-        self.assertEqual(str(nodes), f'Nodes({self.ent_type}, {self.ent_ids})')
-        self.assertEqual(repr(nodes), f'Nodes({self.backend}, {self.user}, {self.ent_type}, {self.ent_ids})')
+        nodes = Nodes(self.backend, self.ac, self.ent_type, {URI('http://example.com/me/entity#1234')})
+        self.assertEqual(str(nodes), f"Nodes({self.ent_type}, {{'http://example.com/me/entity#1234'}})")
+        self.assertEqual(repr(nodes), f"Nodes({self.backend}, {self.ac}, {self.ent_type}, {{'http://example.com/me/entity#1234'}})")
         # str respects node_type
-        nodes = Nodes(self.backend, self.user, self.tag_type, self.tag_ids)
-        self.assertEqual(str(nodes), f'Nodes({self.tag_type}, {self.tag_ids})')
-        self.assertEqual(repr(nodes), f'Nodes({self.backend}, {self.user}, {self.tag_type}, {self.tag_ids})')
+        nodes = Nodes(self.backend, self.ac, self.tag_type, {URI('http://example.com/me/tag#1234')})
+        self.assertEqual(str(nodes), f"Nodes({self.tag_type}, {{'http://example.com/me/tag#1234'}})")
+        self.assertEqual(repr(nodes), f"Nodes({self.backend}, {self.ac}, {self.tag_type}, {{'http://example.com/me/tag#1234'}})")
         # str respects guids
-        nodes = Nodes(self.backend, self.user, self.ent_type, {URI('http://example.com/me/entity#foo')})
+        nodes = Nodes(self.backend, self.ac, self.ent_type, {URI('http://example.com/me/entity#foo')})
         self.assertEqual(str(nodes), f'Nodes({self.ent_type}, {{\'http://example.com/me/entity#foo\'}})')
-        self.assertEqual(repr(nodes), f'Nodes({self.backend}, {self.user}, {self.ent_type}, {{\'http://example.com/me/entity#foo\'}})')
+        self.assertEqual(repr(nodes), f'Nodes({self.backend}, {self.ac}, {self.ent_type}, {{\'http://example.com/me/entity#foo\'}})')
         # repr respects backend
         class Foo(SparqlStore): pass
         backend = Foo.Open()
         backend.schema = self.backend.schema
-        nodes = Nodes(backend, self.user, self.ent_type, self.ent_ids)
-        self.assertEqual(repr(nodes), f'Nodes({backend}, {self.user}, {self.ent_type}, {self.ent_ids})')
+        nodes = Nodes(backend, self.ac, self.ent_type, {URI('http://example.com/me/entity#1234')})
+        self.assertEqual(repr(nodes), f"Nodes({backend}, {self.ac}, {self.ent_type}, {{'http://example.com/me/entity#1234'}})")
         # repr respects user
-        nodes = Nodes(self.backend, URI('http://example.com/you'), self.ent_type, self.ent_ids)
-        self.assertEqual(repr(nodes), f'Nodes({self.backend}, http://example.com/you, {self.ent_type}, {self.ent_ids})')
+        nodes = Nodes(self.backend, NullAC(self.backend, URI('http://example.com/you')), self.ent_type, {URI('http://example.com/me/entity#1234')})
+        self.assertEqual(repr(nodes), f"Nodes({self.backend}, NullAC(http://example.com/you), {self.ent_type}, {{'http://example.com/me/entity#1234'}})")
 
     def test_equality(self):
-        nodes = Nodes(self.backend, self.user, self.ent_type, self.ent_ids)
+        nodes = Nodes(self.backend, self.ac, self.ent_type, self.ent_ids)
         # instance is equal to itself
         self.assertEqual(nodes, nodes)
         self.assertEqual(hash(nodes), hash(nodes))
         # instance is equal to a clone
-        self.assertEqual(nodes, Nodes(self.backend, self.user, self.ent_type, self.ent_ids))
-        self.assertEqual(Nodes(self.backend, self.user, self.ent_type, self.ent_ids), nodes)
-        self.assertEqual(hash(nodes), hash(Nodes(self.backend, self.user, self.ent_type, self.ent_ids)))
+        self.assertEqual(nodes, Nodes(self.backend, self.ac, self.ent_type, self.ent_ids))
+        self.assertEqual(Nodes(self.backend, self.ac, self.ent_type, self.ent_ids), nodes)
+        self.assertEqual(hash(nodes), hash(Nodes(self.backend, self.ac, self.ent_type, self.ent_ids)))
         # equality respects backend
         backend = SparqlStore.Open()
         backend.schema = self.backend.schema
-        self.assertNotEqual(nodes, Nodes(backend, self.user, self.ent_type, self.ent_ids))
-        self.assertNotEqual(hash(nodes), hash(Nodes(backend, self.user, self.ent_type, self.ent_ids)))
+        self.assertNotEqual(nodes, Nodes(backend, self.ac, self.ent_type, self.ent_ids))
+        self.assertNotEqual(hash(nodes), hash(Nodes(backend, self.ac, self.ent_type, self.ent_ids)))
         # equality respects user
-        self.assertNotEqual(nodes, Nodes(self.backend, URI('http://example.com/you'), self.ent_type, self.ent_ids))
-        self.assertNotEqual(hash(nodes), hash(Nodes(self.backend, URI('http://example.com/you'), self.ent_type, self.ent_ids)))
+        self.assertNotEqual(nodes, Nodes(self.backend, NullAC(self.backend, URI('http://example.com/you')), self.ent_type, self.ent_ids))
+        self.assertNotEqual(hash(nodes), hash(Nodes(self.backend, NullAC(self.backend, URI('http://example.com/you')), self.ent_type, self.ent_ids)))
         # equality respects node_type
-        self.assertNotEqual(nodes, Nodes(self.backend, self.user, self.tag_type, self.ent_ids))
-        self.assertNotEqual(hash(nodes), hash(Nodes(self.backend, self.user, self.tag_type, self.ent_ids)))
+        self.assertNotEqual(nodes, Nodes(self.backend, self.ac, self.tag_type, self.ent_ids))
+        self.assertNotEqual(hash(nodes), hash(Nodes(self.backend, self.ac, self.tag_type, self.ent_ids)))
         # equality respects guids
-        self.assertNotEqual(nodes, Nodes(self.backend, self.user, self.ent_type, self.tag_ids))
-        self.assertNotEqual(hash(nodes), hash(Nodes(self.backend, self.user, self.ent_type, self.tag_ids)))
+        self.assertNotEqual(nodes, Nodes(self.backend, self.ac, self.ent_type, self.tag_ids))
+        self.assertNotEqual(hash(nodes), hash(Nodes(self.backend, self.ac, self.ent_type, self.tag_ids)))
 
     def test_properties(self):
         # node_type
         self.assertEqual(self.ent_type, Nodes(
-            self.backend, self.user, self.ent_type, self.ent_ids).node_type)
+            self.backend, self.ac, self.ent_type, self.ent_ids).node_type)
         self.assertEqual(self.tag_type, Nodes(
-            self.backend, self.user, self.tag_type, self.tag_ids).node_type)
+            self.backend, self.ac, self.tag_type, self.tag_ids).node_type)
         # guids
         self.assertSetEqual(self.ent_ids, set(Nodes(
-            self.backend, self.user, self.ent_type, self.ent_ids).guids))
+            self.backend, self.ac, self.ent_type, self.ent_ids).guids))
         self.assertSetEqual(self.tag_ids, set(Nodes(
-            self.backend, self.user, self.tag_type, self.tag_ids).guids))
+            self.backend, self.ac, self.tag_type, self.tag_ids).guids))
 
     def test__ensure_nodes(self):
-        nodes = Nodes(self.backend, self.user, self.ent_type, self.ent_ids)
+        nodes = Nodes(self.backend, self.ac, self.ent_type, self.ent_ids)
 
         # missing nodes are created
         self.assertSetEqual(self.ent_ids, nodes._ensure_nodes(self.ent_type, self.ent_ids))
@@ -196,8 +199,8 @@ class TestNodes(unittest.TestCase):
         # check triples
         self.assertSetEqual(set(self.backend._graph), self.schema_triples | {
             # entity definitions
-            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
-            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
             # bookkeeping
             (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_ent_created, datatype=rdflib.XSD.integer)),
             (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_ent_created, datatype=rdflib.XSD.integer)),
@@ -207,8 +210,8 @@ class TestNodes(unittest.TestCase):
         self.assertSetEqual(self.ent_ids, nodes._ensure_nodes(self.ent_type, self.ent_ids))
         self.assertSetEqual(set(self.backend._graph), self.schema_triples | {
             # entity definitions
-            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
-            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
             # bookkeeping
             (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_ent_created, datatype=rdflib.XSD.integer)),
             (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_ent_created, datatype=rdflib.XSD.integer)),
@@ -222,20 +225,20 @@ class TestNodes(unittest.TestCase):
         # check triples
         self.assertSetEqual(set(self.backend._graph), self.schema_triples | {
             # previous triples
-            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
-            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
             (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_ent_created, datatype=rdflib.XSD.integer)),
             (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_ent_created, datatype=rdflib.XSD.integer)),
             # new triples
-            (rdflib.URIRef('http://example.com/me/tag#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Tag')),
-            (rdflib.URIRef('http://example.com/me/tag#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Tag')),
+            (rdflib.URIRef('http://example.com/me/tag#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Tag')),
+            (rdflib.URIRef('http://example.com/me/tag#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Tag')),
             (rdflib.URIRef('http://example.com/me/tag#1234'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_tag_created, datatype=rdflib.XSD.integer)),
             (rdflib.URIRef('http://example.com/me/tag#4321'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_tag_created, datatype=rdflib.XSD.integer)),
             })
 
     def test___set(self):
         # setup
-        nodes = Nodes(self.backend, self.user, self.ent_type, {URI('http://example.com/me/entity#1234'), URI('http://example.com/me/entity#4321')})
+        nodes = Nodes(self.backend, self.ac, self.ent_type, {URI('http://example.com/me/entity#1234'), URI('http://example.com/me/entity#4321')})
         self.assertSetEqual(set(self.backend._graph), self.schema_triples | set())
         set_ = nodes._Nodes__set
 
@@ -253,8 +256,8 @@ class TestNodes(unittest.TestCase):
         # verify triples
         self.assertSetEqual(set(self.backend._graph), self.schema_triples | {
             # entity definitions
-            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
-            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
             # bookkeeping
             (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_ent_created, datatype=rdflib.XSD.integer)),
             (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_ent_created, datatype=rdflib.XSD.integer)),
@@ -264,7 +267,7 @@ class TestNodes(unittest.TestCase):
             })
 
         # set node value
-        tags = Nodes(self.backend, self.user, self.tag_type, {URI('http://example.com/me/tag#1234'), URI('http://example.com/me/tag#4321')})
+        tags = Nodes(self.backend, self.ac, self.tag_type, {URI('http://example.com/me/tag#1234'), URI('http://example.com/me/tag#4321')})
         set_(self.p_tag.uri, tags)
         # get creation time from backend manually
         time_triples = list(self.backend._graph.objects(rdflib.URIRef('http://example.com/me/tag#1234'), rdflib.URIRef(self.t_created.uri)))
@@ -272,15 +275,15 @@ class TestNodes(unittest.TestCase):
         # verify triples
         self.assertSetEqual(set(self.backend._graph), self.schema_triples | {
             # previous values
-            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
-            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
             (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(self.p_filesize.uri), rdflib.Literal(1234, datatype=rdflib.XSD.integer)),
             (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.URIRef(self.p_filesize.uri), rdflib.Literal(1234, datatype=rdflib.XSD.integer)),
             (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_ent_created, datatype=rdflib.XSD.integer)),
             (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_ent_created, datatype=rdflib.XSD.integer)),
             # tag definitions
-            (rdflib.URIRef('http://example.com/me/tag#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Tag')),
-            (rdflib.URIRef('http://example.com/me/tag#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Tag')),
+            (rdflib.URIRef('http://example.com/me/tag#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Tag')),
+            (rdflib.URIRef('http://example.com/me/tag#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Tag')),
             # tag bookkeeping
             (rdflib.URIRef('http://example.com/me/tag#1234'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_tag_created, datatype=rdflib.XSD.integer)),
             (rdflib.URIRef('http://example.com/me/tag#4321'), rdflib.URIRef(self.t_created.uri), rdflib.Literal(t_tag_created, datatype=rdflib.XSD.integer)),
@@ -296,29 +299,29 @@ class TestNodes(unittest.TestCase):
         self.assertRaises(TypeError, set_, self.p_tag.uri, URI('http://example.com/me/tag#1234'))
         # value's node_type must match the predicate's range
         self.assertRaises(errors.ConsistencyError, set_, self.p_tag.uri,
-            Nodes(self.backend, self.user, self.ent_type, self.ent_ids))
+            Nodes(self.backend, self.ac, self.ent_type, self.ent_ids))
 
     def test_set(self):
         self.assertSetEqual(set(self.backend._graph), self.schema_triples | set())
-        nodes = Nodes(self.backend, self.user, self.ent_type, self.ent_ids)
+        nodes = Nodes(self.backend, self.ac, self.ent_type, self.ent_ids)
         # can set literal values
         self.assertEqual(nodes, nodes.set(self.p_filesize.uri, 1234))
         self.assertTrue(set(self.backend._graph).issuperset({
             # nodes exist
-            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
-            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
             # links exist
             (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(self.p_filesize.uri), rdflib.Literal(1234, datatype=rdflib.XSD.integer)),
             (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.URIRef(self.p_filesize.uri), rdflib.Literal(1234, datatype=rdflib.XSD.integer)),
             }))
         # can set node values
-        self.assertEqual(nodes, nodes.set(self.p_tag.uri, Nodes(self.backend, self.user, self.tag_type, self.tag_ids)))
+        self.assertEqual(nodes, nodes.set(self.p_tag.uri, Nodes(self.backend, self.ac, self.tag_type, self.tag_ids)))
         self.assertTrue(set(self.backend._graph).issuperset({
             # nodes exist
-            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
-            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
-            (rdflib.URIRef('http://example.com/me/tag#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Tag')),
-            (rdflib.URIRef('http://example.com/me/tag#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Tag')),
+            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
+            (rdflib.URIRef('http://example.com/me/tag#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Tag')),
+            (rdflib.URIRef('http://example.com/me/tag#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Tag')),
             # links exist
             (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(self.p_tag.uri), rdflib.URIRef('http://example.com/me/tag#1234')),
             (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(self.p_tag.uri), rdflib.URIRef('http://example.com/me/tag#4321')),
@@ -341,24 +344,28 @@ class TestNodes(unittest.TestCase):
         self.assertSetEqual(curr, set(self.backend._graph))
         # cannot assing multiple values to unique predicate
         self.assertRaises(ValueError, nodes.set, self.p_author.uri,
-            Nodes(self.backend, self.user, self.user_type, {URI('http://example.com/me/user#1234'), URI('http://example.com/me/user#4321')}))
+            Nodes(self.backend, self.ac, self.user_type, {URI('http://example.com/me/user#1234'), URI('http://example.com/me/user#4321')}))
         self.assertSetEqual(curr, set(self.backend._graph))
 
+        # can set on empty nodes
+        nodes = Nodes(self.backend, self.ac, self.ent_type, {})
+        self.assertEqual(nodes, nodes.set(self.p_filesize.uri, 1234))
+
 
     def test_set_from_iterable(self):
         self.assertSetEqual(set(self.backend._graph), self.schema_triples | set())
-        nodes = Nodes(self.backend, self.user, self.ent_type, self.ent_ids)
+        nodes = Nodes(self.backend, self.ac, self.ent_type, self.ent_ids)
         # can set literal and node values simultaneously
         self.assertEqual(nodes, nodes.set_from_iterable({
             self.p_filesize.uri: 1234,
-            self.p_tag.uri: Nodes(self.backend, self.user, self.tag_type, self.tag_ids),
+            self.p_tag.uri: Nodes(self.backend, self.ac, self.tag_type, self.tag_ids),
             }.items()))
         self.assertTrue(set(self.backend._graph).issuperset({
             # nodes exist
-            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
-            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')),
-            (rdflib.URIRef('http://example.com/me/tag#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Tag')),
-            (rdflib.URIRef('http://example.com/me/tag#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Tag')),
+            (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
+            (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')),
+            (rdflib.URIRef('http://example.com/me/tag#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Tag')),
+            (rdflib.URIRef('http://example.com/me/tag#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Tag')),
             # links exist
             (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(self.p_filesize.uri), rdflib.Literal(1234, datatype=rdflib.XSD.integer)),
             (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.URIRef(self.p_filesize.uri), rdflib.Literal(1234, datatype=rdflib.XSD.integer)),
@@ -383,24 +390,30 @@ class TestNodes(unittest.TestCase):
         self.assertSetEqual(curr, set(self.backend._graph))
         # cannot assing multiple values to unique predicate
         self.assertRaises(ValueError, nodes.set_from_iterable, ((self.p_filesize.uri, 1234),
-            (self.p_author.uri, Nodes(self.backend, self.user, self.user_type, {URI('http://example.com/me/user#1234'), URI('http://example.com/me/user#4321')}))))
+            (self.p_author.uri, Nodes(self.backend, self.ac, self.user_type, {URI('http://example.com/me/user#1234'), URI('http://example.com/me/user#4321')}))))
         self.assertSetEqual(curr, set(self.backend._graph))
 
+        # can set on empty nodes
+        nodes = Nodes(self.backend, self.ac, self.ent_type, {})
+        self.assertEqual(nodes, nodes.set_from_iterable([(self.p_filesize.uri, 1234)]))
+
+
     def test_get(self):
         # setup: add some instances
-        Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#1234'}) \
+        Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#1234'}) \
             .set(ns.bse.comment, 'hello world') \
             .set(ns.bse.filesize, 1234) \
-            .set(ns.bse.tag, Nodes(self.backend, self.user, self.tag_type, {'http://example.com/me/tag#1234'}))
-        Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#4321'}) \
+            .set(ns.bse.tag, Nodes(self.backend, self.ac, self.tag_type, {'http://example.com/me/tag#1234'}))
+        Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#4321'}) \
             .set(ns.bse.filesize, 4321) \
-            .set(ns.bse.tag, Nodes(self.backend, self.user, self.tag_type, {'http://example.com/me/tag#4321'}))
-        Nodes(self.backend, self.user, self.tag_type, {'http://example.com/me/tag#1234'}) \
-            .set(bst.label, 'tag_label_1234')
-        Nodes(self.backend, self.user, self.tag_type, {'http://example.com/me/tag#4321'}) \
-            .set(bst.label, 'tag_label_4321')
+            .set(ns.bse.tag, Nodes(self.backend, self.ac, self.tag_type, {'http://example.com/me/tag#4321'}))
+        Nodes(self.backend, self.ac, self.tag_type, {'http://example.com/me/tag#1234'}) \
+            .set(ns.bst.label, 'tag_label_1234')
+        Nodes(self.backend, self.ac, self.tag_type, {'http://example.com/me/tag#4321'}) \
+            .set(ns.bst.label, 'tag_label_4321')
         # setup: get nodes instance
-        nodes = Nodes(self.backend, self.user, self.ent_type, self.ent_ids)
+        nodes = Nodes(self.backend, self.ac, self.ent_type, self.ent_ids)
+
         # must pass at least one path
         self.assertRaises(AttributeError, nodes.get)
         # view must be list or dict
@@ -409,69 +422,112 @@ class TestNodes(unittest.TestCase):
         self.assertRaises(ValueError, nodes.get, ns.bse.filesize, view=tuple)
         # can pass path as URI
         self.assertDictEqual(nodes.get(ns.bse.filesize), {
-            Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#1234'}): 1234,
-            Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#4321'}): 4321,
+            Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#1234'}): 1234,
+            Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#4321'}): 4321,
             })
         # can pass path as sequence of URI
-        self.assertDictEqual(nodes.get((ns.bse.tag, bst.label)), {
-            Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#1234'}): {'tag_label_1234'},
-            Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#4321'}): {'tag_label_4321'},
+        self.assertDictEqual(nodes.get((ns.bse.tag, ns.bst.label)), {
+            Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#1234'}): {'tag_label_1234'},
+            Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#4321'}): {'tag_label_4321'},
             })
         # get returns the same path that was passed
-        self.assertCountEqual(list(nodes.get((ns.bse.tag, bst.label), path=True, view=list)), [
-            (Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#1234'}), (ns.bse.tag, bst.label), 'tag_label_1234'),
-            (Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#4321'}), (ns.bse.tag, bst.label), 'tag_label_4321'),
+        self.assertCountEqual(list(nodes.get((ns.bse.tag, ns.bst.label), path=True, view=list)), [
+            (Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#1234'}), (ns.bse.tag, ns.bst.label), 'tag_label_1234'),
+            (Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#4321'}), (ns.bse.tag, ns.bst.label), 'tag_label_4321'),
             ])
-        self.assertCountEqual(list(nodes.get([ns.bse.tag, bst.label], path=True, view=list)), [
-            (Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#1234'}), [ns.bse.tag, bst.label], 'tag_label_1234'),
-            (Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#4321'}), [ns.bse.tag, bst.label], 'tag_label_4321'),
+        self.assertCountEqual(list(nodes.get([ns.bse.tag, ns.bst.label], path=True, view=list)), [
+            (Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#1234'}), [ns.bse.tag, ns.bst.label], 'tag_label_1234'),
+            (Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#4321'}), [ns.bse.tag, ns.bst.label], 'tag_label_4321'),
             ])
         # paths must be URI or sequence thereof
         self.assertRaises(TypeError, nodes.get, 1234)
         self.assertRaises(TypeError, nodes.get, (ns.bse.tag, 1234))
         self.assertRaises(TypeError, nodes.get, (1234, ns.bse.tag))
-        self.assertRaises(errors.ConsistencyError, nodes.get, 'hello world')
+        self.assertRaises(ValueError, nodes.get, 'hello world')
+        self.assertRaises(errors.ConsistencyError, nodes.get, 'hello_world')
         self.assertRaises(errors.ConsistencyError, nodes.get, ns.bse.invalid)
-        self.assertRaises(errors.ConsistencyError, nodes.get, (ns.bse.tag, bst.invalid))
+        self.assertRaises(errors.ConsistencyError, nodes.get, (ns.bse.tag, ns.bst.invalid))
         # can pass multiple paths
-        self.assertDictEqual(nodes.get(ns.bse.filesize, (ns.bse.tag, bst.label)), {
-            Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#1234'}): {
+        self.assertDictEqual(nodes.get(ns.bse.filesize, (ns.bse.tag, ns.bst.label)), {
+            Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#1234'}): {
                 ns.bse.filesize: 1234,
-                (ns.bse.tag, bst.label): {'tag_label_1234'},
+                (ns.bse.tag, ns.bst.label): {'tag_label_1234'},
                 },
-            Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#4321'}): {
+            Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#4321'}): {
                 ns.bse.filesize: 4321,
-                (ns.bse.tag, bst.label): {'tag_label_4321'},
+                (ns.bse.tag, ns.bst.label): {'tag_label_4321'},
                 },
             })
         # get respects view
         self.assertDictEqual(nodes.get(ns.bse.filesize, view=dict), {
-            Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#1234'}): 1234,
-            Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#4321'}): 4321,
+            Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#1234'}): 1234,
+            Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#4321'}): 4321,
             })
         self.assertSetEqual(set(nodes.get(ns.bse.filesize, view=list)), {
-            (Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#1234'}), 1234),
-            (Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#4321'}), 4321),
+            (Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#1234'}), 1234),
+            (Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#4321'}), 4321),
             })
         # get returns Nodes instance when fetching a node
         self.assertDictEqual(nodes.get(ns.bse.tag), {
-            Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#1234'}):
-                {Nodes(self.backend, self.user, self.tag_type, {'http://example.com/me/tag#1234'})},
-            Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#4321'}):
-                {Nodes(self.backend, self.user, self.tag_type, {'http://example.com/me/tag#4321'})},
+            Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#1234'}):
+                {Nodes(self.backend, self.ac, self.tag_type, {'http://example.com/me/tag#1234'})},
+            Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#4321'}):
+                {Nodes(self.backend, self.ac, self.tag_type, {'http://example.com/me/tag#4321'})},
             })
         # get returns a value when fetching a value and omits missing values
         self.assertDictEqual(nodes.get(ns.bse.comment), {
-            Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#1234'}): {'hello world'},
+            Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#1234'}): {'hello world'},
             })
 
-        # FIXME: What if I call `get` with a single predicate and a single node, but
-        # that node has no value for that predicate?
-        # so, essentially, what if triples is empty? -> Also check in test_result!
-        raise NotImplementedError()
+        # results can be empty
+        nodes = Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#4321'}) # has filesize, tag but no comment
+        # unique paths return the default value
+        self.assertIsNone(nodes.get(ns.bse.author))
+        self.assertEqual(nodes.get(ns.bse.author, default=1234), 1234)
+        # non-unique paths return an empty set
+        self.assertSetEqual(nodes.get(ns.bse.comment), set())
+
+        # nodes can have no guids
+        nodes = Nodes(self.backend, self.ac, self.ent_type, set())
+        # empty nodes does not excuse an invalid request
+        self.assertRaises(TypeError, nodes.get, 1234)
+        self.assertRaises(errors.ConsistencyError, nodes.get, ns.bse.invalid)
+        # list view always returns an empty list
+        self.assertListEqual(list(nodes.get(ns.bse.comment, view=list)), [])
+        self.assertListEqual(list(nodes.get(ns.bse.comment, view=list, node=True)), [])
+        self.assertListEqual(list(nodes.get(ns.bse.comment, view=list, path=True)), [])
+        self.assertListEqual(list(nodes.get(ns.bse.comment, view=list, node=True, path=True, value=True)), [])
+        self.assertListEqual(list(nodes.get(ns.bse.comment, view=list, node=False)), [])
+        self.assertListEqual(list(nodes.get(ns.bse.comment, view=list, path=False)), [])
+        self.assertListEqual(list(nodes.get(ns.bse.comment, view=list, node=False, path=False, value=False)), [])
+        self.assertListEqual(list(nodes.get(ns.bse.comment, ns.bse.filesize, view=list)), [])
+        self.assertListEqual(list(nodes.get(ns.bse.comment, ns.bse.filesize, view=list, node=True)), [])
+        self.assertListEqual(list(nodes.get(ns.bse.comment, ns.bse.filesize, view=list, path=True)), [])
+        self.assertListEqual(list(nodes.get(ns.bse.comment, ns.bse.filesize, view=list, node=True, path=True, value=True)), [])
+        self.assertListEqual(list(nodes.get(ns.bse.comment, ns.bse.filesize, view=list, node=False)), [])
+        self.assertListEqual(list(nodes.get(ns.bse.comment, ns.bse.filesize, view=list, path=False)), [])
+        self.assertListEqual(list(nodes.get(ns.bse.comment, ns.bse.filesize, view=list, node=False, path=False, value=False)), [])
+        # dict view returns an empty dict or an empty set
+        self.assertDictEqual(nodes.get(ns.bse.comment, view=dict), {})
+        self.assertDictEqual(nodes.get(ns.bse.comment, view=dict, node=True), {})
+        self.assertDictEqual(nodes.get(ns.bse.comment, view=dict, path=True), {})
+        self.assertDictEqual(nodes.get(ns.bse.comment, view=dict, node=True, path=True, value=True, default=None), {})
+        self.assertSetEqual(nodes.get(ns.bse.comment, view=dict, node=False), set())
+        self.assertDictEqual(nodes.get(ns.bse.comment, view=dict, path=False), {})
+        self.assertSetEqual(nodes.get(ns.bse.comment, view=dict, node=False, path=False), set())
+        self.assertSetEqual(nodes.get(ns.bse.comment, view=dict, node=False, path=False, value=False, default=None), set())
+        self.assertDictEqual(nodes.get(ns.bse.comment, ns.bse.filesize, view=dict), {})
+        self.assertDictEqual(nodes.get(ns.bse.comment, ns.bse.filesize, view=dict, node=True), {})
+        self.assertDictEqual(nodes.get(ns.bse.comment, ns.bse.filesize, view=dict, path=True), {})
+        self.assertDictEqual(nodes.get(ns.bse.comment, ns.bse.filesize, view=dict, node=True, path=True, value=True, default=None), {})
+        self.assertDictEqual(nodes.get(ns.bse.comment, ns.bse.filesize, view=dict, node=False), {})
+        self.assertDictEqual(nodes.get(ns.bse.comment, ns.bse.filesize, view=dict, path=False), {})
+        self.assertSetEqual(nodes.get(ns.bse.comment, ns.bse.filesize, view=dict, node=False, path=False), set())
+        self.assertSetEqual(nodes.get(ns.bse.comment, ns.bse.filesize, view=dict, node=False, path=False, value=False, default=None), set())
+
 
     def test_getattr(self):
-        nodes = Nodes(self.backend, self.user, self.ent_type, {'http://example.com/me/entity#1234'})
+        nodes = Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#1234'})
         # can get walks to values
         self.assertEqual(nodes.filesize, Walk(nodes, (self.p_filesize, )))
         # can get walks to nodes
@@ -482,11 +538,11 @@ class TestNodes(unittest.TestCase):
         self.assertRaises(ValueError, getattr, nodes, 'foobar')
 
     def test_schema(self):
-        self.assertEqual(Nodes(self.backend, self.user, self.ent_type,
+        self.assertEqual(Nodes(self.backend, self.ac, self.ent_type,
             {URI('http://example.com/me/entity#1234')}).schema, self.backend.schema)
 
     def test_operators(self): # __add__, __or__, __sub__, __and__
-        gen = partial(Nodes, self.backend, self.user, self.ent_type)
+        gen = partial(Nodes, self.backend, self.ac, self.ent_type)
         nodes = gen({URI('http://example.com/me/entity#1234')})
         # add/or concatenates guids
         self.assertEqual(
@@ -544,23 +600,24 @@ class TestNodes(unittest.TestCase):
             self.assertRaises(TypeError, op, nodes, 'hello world')
             # backend must match
             self.assertRaises(ValueError, op, nodes,
-                Nodes(None, self.user, self.ent_type, {URI('http://example.com/me/entity#1234')}))
-            # user must match
+                Nodes(None, self.ac, self.ent_type, {URI('http://example.com/me/entity#1234')}))
+            # ac must match
             self.assertRaises(ValueError, op, nodes,
-                Nodes(self.backend, '', self.ent_type, {URI('http://example.com/me/entity#1234')}))
+                Nodes(self.backend, NullAC(self.backend, ''),
+                    self.ent_type, {URI('http://example.com/me/entity#1234')}))
             # node type must match
             self.assertRaises(ValueError, op, nodes,
-                Nodes(self.backend, self.user, self.tag_type, {URI('http://example.com/me/entity#1234')}))
+                Nodes(self.backend, self.ac, self.tag_type, {URI('http://example.com/me/entity#1234')}))
 
     def test_len(self):
-        self.assertEqual(1, len(Nodes(self.backend, self.user, self.ent_type, {
+        self.assertEqual(1, len(Nodes(self.backend, self.ac, self.ent_type, {
             URI('http://example.com/me/entity#1234'),
             })))
-        self.assertEqual(2, len(Nodes(self.backend, self.user, self.ent_type, {
+        self.assertEqual(2, len(Nodes(self.backend, self.ac, self.ent_type, {
             URI('http://example.com/me/entity#1234'),
             URI('http://example.com/me/entity#4321'),
             })))
-        self.assertEqual(4, len(Nodes(self.backend, self.user, self.ent_type, {
+        self.assertEqual(4, len(Nodes(self.backend, self.ac, self.ent_type, {
             URI('http://example.com/me/entity#1234'),
             URI('http://example.com/me/entity#4321'),
             URI('http://example.com/me/entity#5678'),
@@ -568,8 +625,8 @@ class TestNodes(unittest.TestCase):
             })))
 
     def test_iter(self): # __iter__
-        gen = partial(Nodes, self.backend, self.user, self.ent_type)
-        self.assertSetEqual(set(Nodes(self.backend, self.user, self.ent_type, {
+        gen = partial(Nodes, self.backend, self.ac, self.ent_type)
+        self.assertSetEqual(set(Nodes(self.backend, self.ac, self.ent_type, {
             URI('http://example.com/me/entity#1234'),
             URI('http://example.com/me/entity#4321'),
             URI('http://example.com/me/entity#5678'),
diff --git a/test/graph/test_resolve.py b/test/graph/test_resolve.py
index 0918b02..e09b1cc 100644
--- a/test/graph/test_resolve.py
+++ b/test/graph/test_resolve.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import unittest
 
@@ -21,6 +16,8 @@ from bsfs.graph.resolve import Filter
 
 ## code ##
 
+ns.bse = ns.bsfs.Entity()
+
 class TestFilter(unittest.TestCase):
     """
 
@@ -30,23 +27,25 @@ class TestFilter(unittest.TestCase):
 
     """
 
-    def test_call(self):
+    def test_call(self): # tests resolve implicitly
         schema = bsc.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
 
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsa: <https://schema.bsfs.io/core/Literal/Array/>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Tag rdfs:subClassOf bsfs:Node .
             xsd:string rdfs:subClassOf bsfs:Literal .
-            bsfs:Number rdfs:subClassOf bsfs:Literal .
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array .
-            xsd:integer rdfs:subClassOf bsfs:Number .
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            bsa:Feature rdfs:subClassOf bsl:Array .
+            xsd:integer rdfs:subClassOf bsl:Number .
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
+            bsfs:Colors rdfs:subClassOf bsa:Feature ;
                 bsfs:dimension "5"^^xsd:integer .
 
             bse:colors rdfs:subClassOf bsfs:Predicate ;
@@ -79,6 +78,9 @@ class TestFilter(unittest.TestCase):
             {'http://example.com/you/invalid#1234', 'http://example.com/you/invalid#4321'})
         resolver = Filter(schema)
 
+        # query can be None
+        self.assertIsNone(resolver(schema.node(ns.bsfs.Entity), None))
+
         # immediate Is
         self.assertEqual(resolver(schema.node(ns.bsfs.Entity),
             ast.filter.Is(ents)),
diff --git a/test/graph/test_result.py b/test/graph/test_result.py
index 749b8ad..8960ef6 100644
--- a/test/graph/test_result.py
+++ b/test/graph/test_result.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import unittest
 
@@ -18,6 +13,8 @@ from bsfs.graph.result import to_list_view, to_dict_view
 
 ## code ##
 
+ns.bse = ns.bsfs.Entity()
+
 class TestListView(unittest.TestCase):
     def setUp(self):
         self.triples_111 = [('ent#1234', ns.bse.iso, 123)]
diff --git a/test/graph/test_walk.py b/test/graph/test_walk.py
index f9dbc7a..4b844da 100644
--- a/test/graph/test_walk.py
+++ b/test/graph/test_walk.py
@@ -1,15 +1,11 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import unittest
 
 # bsfs imports
 from bsfs import schema as bsc
 from bsfs.graph import Graph
+from bsfs.graph.ac import NullAC
 from bsfs.namespace import Namespace, ns
 from bsfs.triple_store.sparql import SparqlStore
 from bsfs.utils import URI
@@ -19,8 +15,8 @@ from bsfs.graph.walk import Walk
 
 ## code ##
 
-bse = ns.bse
-bst = Namespace('http://bsfs.ai/schema/Tag')
+ns.bse = ns.bsfs.Entity()
+ns.bst = ns.bsfs.Tag()
 
 class TestWalk(unittest.TestCase):
     def setUp(self):
@@ -28,9 +24,9 @@ class TestWalk(unittest.TestCase):
         self.schema = bsc.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
-            prefix bst: <http://bsfs.ai/schema/Tag#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bst: <https://schema.bsfs.io/core/Tag#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Tag rdfs:subClassOf bsfs:Node .
@@ -65,7 +61,8 @@ class TestWalk(unittest.TestCase):
             ''')
         self.backend = SparqlStore.Open()
         self.user = URI('http://example.com/me')
-        self.graph = Graph(self.backend, self.user)
+        self.ac = NullAC(self.backend, self.user)
+        self.graph = Graph(self.backend, self.ac)
         self.graph.migrate(self.schema)
 
         # nodes setup
@@ -76,14 +73,14 @@ class TestWalk(unittest.TestCase):
             URI('http://example.com/me/tag#1234'),
             URI('http://example.com/me/tag#4321')})
         # add some instances
-        self.ents.set(bse.tag, self.tags)
-        self.graph.node(ns.bsfs.Tag, URI('http://example.com/me/tag#1234')).set(bst.label, 'hello')
-        self.graph.node(ns.bsfs.Tag, URI('http://example.com/me/tag#4321')).set(bst.label, 'world')
+        self.ents.set(ns.bse.tag, self.tags)
+        self.graph.node(ns.bsfs.Tag, URI('http://example.com/me/tag#1234')).set(ns.bst.label, 'hello')
+        self.graph.node(ns.bsfs.Tag, URI('http://example.com/me/tag#4321')).set(ns.bst.label, 'world')
 
     def test_essentials(self): # __eq__, __hash__, __str__, __repr__
-        p_author = self.schema.predicate(bse.author)
-        p_tag = self.schema.predicate(bse.tag)
-        p_main = self.schema.predicate(bst.main)
+        p_author = self.schema.predicate(ns.bse.author)
+        p_tag = self.schema.predicate(ns.bse.tag)
+        p_main = self.schema.predicate(ns.bst.main)
         # comparison
         self.assertEqual(Walk(self.ents, [p_tag]), Walk(self.ents, [p_tag]))
         self.assertEqual(hash(Walk(self.ents, [p_tag])), hash(Walk(self.ents, [p_tag])))
@@ -99,18 +96,18 @@ class TestWalk(unittest.TestCase):
         self.assertNotEqual(hash(Walk(self.tags, [p_author])), hash(Walk(self.tags, [p_main])))
         # string conversion
         self.assertEqual(str(Walk(self.ents, [p_tag, p_main])),
-            'Walk(@http://bsfs.ai/schema/Entity: http://bsfs.ai/schema/Entity#tag, http://bsfs.ai/schema/Tag#main)')
+            'Walk(@https://schema.bsfs.io/core/Entity: https://schema.bsfs.io/core/Entity#tag, https://schema.bsfs.io/core/Tag#main)')
         self.assertEqual(repr(Walk(self.ents, [p_tag, p_main])),
-            'Walk(http://bsfs.ai/schema/Entity, (http://bsfs.ai/schema/Entity#tag, http://bsfs.ai/schema/Tag#main))')
+            'Walk(https://schema.bsfs.io/core/Entity, (https://schema.bsfs.io/core/Entity#tag, https://schema.bsfs.io/core/Tag#main))')
 
     def test_tail(self):
         self.assertEqual(Walk(self.ents, (
-            self.schema.predicate(bse.tag),
+            self.schema.predicate(ns.bse.tag),
             )).tail,
             self.schema.node(ns.bsfs.Tag))
         self.assertEqual(Walk(self.ents, (
-            self.schema.predicate(bse.tag),
-            self.schema.predicate(bst.main),
+            self.schema.predicate(ns.bse.tag),
+            self.schema.predicate(ns.bst.main),
             )).tail,
             self.schema.node(ns.bsfs.Entity))
 
@@ -118,24 +115,24 @@ class TestWalk(unittest.TestCase):
         tag_type = self.schema.node(ns.bsfs.Tag)
         # step returns a predicate
         self.assertEqual(Walk.step(self.schema, tag_type, 'subTagOf'),
-            (self.schema.predicate(bst.subTagOf), ))
+            (self.schema.predicate(ns.bst.subTagOf), ))
         # invalid step raises an error
         self.assertRaises(ValueError, Walk.step, self.schema, tag_type, 'foobar')
         # ambiguous step raises an error
         self.assertRaises(ValueError, Walk.step, self.schema, tag_type, 'author')
 
     def test_getattr(self): # __getattr__
-        walk = Walk(self.ents, (self.schema.predicate(bse.tag), ))
+        walk = Walk(self.ents, (self.schema.predicate(ns.bse.tag), ))
         # first step
         self.assertEqual(walk.subTagOf, Walk(self.ents, (
-            self.schema.predicate(bse.tag),
-            self.schema.predicate(bst.subTagOf),
+            self.schema.predicate(ns.bse.tag),
+            self.schema.predicate(ns.bst.subTagOf),
             )))
         # second step
         self.assertEqual(walk.subTagOf.main, Walk(self.ents, (
-            self.schema.predicate(bse.tag),
-            self.schema.predicate(bst.subTagOf),
-            self.schema.predicate(bst.main),
+            self.schema.predicate(ns.bse.tag),
+            self.schema.predicate(ns.bst.subTagOf),
+            self.schema.predicate(ns.bst.main),
             )))
         # invalid step raises an error
         self.assertRaises(ValueError, getattr, walk, 'foobar')
@@ -143,7 +140,7 @@ class TestWalk(unittest.TestCase):
         self.assertRaises(ValueError, getattr, walk, 'author')
 
     def test_get(self): # get, __call__
-        walk = Walk(self.ents, (self.schema.predicate(bse.tag), ))
+        walk = Walk(self.ents, (self.schema.predicate(ns.bse.tag), ))
         tags = {
             self.graph.node(ns.bsfs.Tag, URI('http://example.com/me/tag#1234')),
             self.graph.node(ns.bsfs.Tag, URI('http://example.com/me/tag#4321'))}
diff --git a/test/namespace/test_namespace.py b/test/namespace/test_namespace.py
index 2536203..f7bf02a 100644
--- a/test/namespace/test_namespace.py
+++ b/test/namespace/test_namespace.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the tagit test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import operator
 import unittest
@@ -12,7 +7,7 @@ import unittest
 from bsfs.utils import URI
 
 # objects to test
-from bsfs.namespace.namespace import Namespace, ClosedNamespace
+from bsfs.namespace.namespace import Namespace, FinalNamespace
 
 
 ## code ##
@@ -20,108 +15,48 @@ from bsfs.namespace.namespace import Namespace, ClosedNamespace
 class TestNamespace(unittest.TestCase):
     def test_essentials(self):
         # string conversion
-        self.assertEqual(str(Namespace('http://example.org/')), 'http://example.org')
-        self.assertEqual(str(Namespace('http://example.org#')), 'http://example.org')
-        self.assertEqual(repr(Namespace('http://example.org/')), 'Namespace(http://example.org, #, /)')
-        self.assertEqual(repr(Namespace('http://example.org#')), 'Namespace(http://example.org, #, /)')
-        self.assertEqual(repr(Namespace('http://example.org', fsep='.')), 'Namespace(http://example.org, ., /)')
-        self.assertEqual(repr(Namespace('http://example.org', psep='.')), 'Namespace(http://example.org, #, .)')
-        # repeated separators are truncated
-        self.assertEqual(str(Namespace('http://example.org////')), 'http://example.org')
-        self.assertEqual(str(Namespace('http://example.org####')), 'http://example.org')
-        self.assertEqual(repr(Namespace('http://example.org///##')), 'Namespace(http://example.org, #, /)')
+        self.assertEqual(str(Namespace('http://example.org')), 'http://example.org')
+        self.assertEqual(repr(Namespace('http://example.org')), "'http://example.org'")
         # comparison
-        class Foo(Namespace): pass
-        self.assertEqual(Namespace('http://example.org/'), Namespace('http://example.org/'))
-        self.assertEqual(Namespace('http://example.org/'), Namespace('http://example.org'))
-        self.assertEqual(Namespace('http://example.org/'), Namespace('http://example.org#'))
-        self.assertNotEqual(Namespace('http://example.org'), Namespace('http://example.org', fsep='.'))
-        self.assertNotEqual(Namespace('http://example.org'), Namespace('http://example.org', psep='.'))
-        self.assertNotEqual(Namespace('http://example.org/'), Foo('http://example.org/'))
-        self.assertNotEqual(Foo('http://example.org/'), Namespace('http://example.org/'))
-        # hashing
-        self.assertEqual(hash(Namespace('http://example.org/')), hash(Namespace('http://example.org/')))
-        self.assertEqual(hash(Namespace('http://example.org/')), hash(Namespace('http://example.org')))
-        self.assertEqual(hash(Namespace('http://example.org/')), hash(Namespace('http://example.org#')))
+        self.assertEqual(Namespace('http://example.org'), Namespace('http://example.org'))
+        self.assertEqual(hash(Namespace('http://example.org')), hash(Namespace('http://example.org')))
+        # Namespace compares to string
+        self.assertEqual(Namespace('http://example.org'), 'http://example.org')
+        self.assertEqual(hash(Namespace('http://example.org')), hash('http://example.org'))
+        # URI must match
+        self.assertNotEqual(Namespace('http://example.org'), Namespace('http://example.com'))
         self.assertNotEqual(hash(Namespace('http://example.org')), hash(Namespace('http://example.com')))
-        self.assertNotEqual(hash(Namespace('http://example.org')), hash(Namespace('http://example.org', fsep='.')))
-        self.assertNotEqual(hash(Namespace('http://example.org')), hash(Namespace('http://example.org', psep='.')))
-        self.assertNotEqual(hash(Namespace('http://example.org/')), hash(Foo('http://example.org/')))
-        self.assertNotEqual(hash(Foo('http://example.org/')), hash(Namespace('http://example.org/')))
 
     def test_getattr(self):
-        self.assertEqual(Namespace('http://example.org/').foo, 'http://example.org#foo')
-        self.assertEqual(Namespace('http://example.org/').bar, 'http://example.org#bar')
-        self.assertEqual(Namespace('http://example.org/', fsep='/').foo, 'http://example.org/foo')
-        self.assertEqual(Namespace('http://example.org/', fsep='/').bar, 'http://example.org/bar')
-        self.assertEqual(Namespace('http://example.org', fsep='/').foo, 'http://example.org/foo')
-        self.assertEqual(Namespace('http://example.org', fsep='/').bar, 'http://example.org/bar')
-        self.assertEqual(Namespace('http://example.org#', fsep='/').foo, 'http://example.org#/foo')
-        self.assertEqual(Namespace('http://example.org#', fsep='/').bar, 'http://example.org#/bar')
-        self.assertEqual(Namespace('http://example.org/me#').foo, 'http://example.org/me#foo')
-        self.assertEqual(Namespace('http://example.org/me#').bar, 'http://example.org/me#bar')
+        self.assertEqual(Namespace('http://example.org').foo, Namespace('http://example.org/foo'))
+        self.assertEqual(Namespace('http://example.org').bar, Namespace('http://example.org/bar'))
 
-    def test_getitem(self):
-        self.assertEqual(Namespace('http://example.org')['foo'], 'http://example.org#foo')
-        self.assertEqual(Namespace('http://example.org')['bar'], 'http://example.org#bar')
-        self.assertEqual(Namespace('http://example.org', fsep='/')['foo'], 'http://example.org/foo')
-        self.assertEqual(Namespace('http://example.org', fsep='/')['bar'], 'http://example.org/bar')
-        self.assertEqual(Namespace('http://example.org/me#')['foo'], 'http://example.org/me#foo')
-        self.assertEqual(Namespace('http://example.org/me#')['bar'], 'http://example.org/me#bar')
+    def test_call(self):
+        self.assertEqual(Namespace('http://example.org')(), FinalNamespace('http://example.org', sep='#'))
+        self.assertEqual(Namespace('http://example.org').foo(), FinalNamespace('http://example.org/foo', sep='#'))
 
-    def test_add(self):
-        self.assertEqual(Namespace('http://example.org') + 'foo', Namespace('http://example.org/foo'))
-        self.assertEqual(Namespace('http://example.org', psep='.') + 'foo', Namespace('http://example.org.foo', psep='.'))
-        self.assertEqual(Namespace('http://example.org') + 'foo' + 'bar', Namespace('http://example.org/foo/bar'))
-        # can add URIs
-        self.assertEqual(Namespace('http://example.org') + URI('foo'), Namespace('http://example.org/foo'))
-        # can only add strings
-        self.assertRaises(TypeError, operator.add, Namespace('http://example.org'), 1234)
-        self.assertRaises(TypeError, operator.add, Namespace('http://example.org'), Namespace('http://example.com'))
-
-
-class TestClosedNamespace(unittest.TestCase):
+class TestFinalNamespace(unittest.TestCase):
     def test_essentials(self):
-       # string conversion
-        self.assertEqual(str(ClosedNamespace('http://example.org/')), 'http://example.org')
-        self.assertEqual(str(ClosedNamespace('http://example.org#')), 'http://example.org')
-        self.assertEqual(repr(ClosedNamespace('http://example.org/')), 'ClosedNamespace(http://example.org, #, /)')
-        self.assertEqual(repr(ClosedNamespace('http://example.org#')), 'ClosedNamespace(http://example.org, #, /)')
-        self.assertEqual(repr(ClosedNamespace('http://example.org', fsep='.')), 'ClosedNamespace(http://example.org, ., /)')
-        self.assertEqual(repr(ClosedNamespace('http://example.org', psep='.')), 'ClosedNamespace(http://example.org, #, .)')
+        # string conversion
+        self.assertEqual(str(FinalNamespace('http://example.org')), 'http://example.org')
+        self.assertEqual(repr(FinalNamespace('http://example.org')), "'http://example.org'")
         # comparison
-        class Foo(ClosedNamespace): pass
-        self.assertEqual(ClosedNamespace('http://example.org'), ClosedNamespace('http://example.org#'))
-        self.assertEqual(ClosedNamespace('http://example.org'), ClosedNamespace('http://example.org'))
-        self.assertEqual(ClosedNamespace('http://example.org'), ClosedNamespace('http://example.org/'))
-        self.assertEqual(ClosedNamespace('http://example.org/', 'foo', 'bar'), ClosedNamespace('http://example.org/', 'foo', 'bar'))
-        self.assertNotEqual(ClosedNamespace('http://example.org/', 'foo'), ClosedNamespace('http://example.org/', 'bar'))
-        self.assertNotEqual(ClosedNamespace('http://example.org/'), Foo('http://example.org/'))
-        self.assertNotEqual(Foo('http://example.org/'), ClosedNamespace('http://example.org/'))
-        # hashing
-        self.assertEqual(hash(ClosedNamespace('http://example.org')), hash(ClosedNamespace('http://example.org')))
-        self.assertEqual(hash(ClosedNamespace('http://example.org')), hash(ClosedNamespace('http://example.org/')))
-        self.assertEqual(hash(ClosedNamespace('http://example.org')), hash(ClosedNamespace('http://example.org#')))
-        self.assertEqual(hash(ClosedNamespace('http://example.org/', 'foo', 'bar')), hash(ClosedNamespace('http://example.org/', 'foo', 'bar')))
-        self.assertNotEqual(hash(ClosedNamespace('http://example.org/', 'foo')), hash(ClosedNamespace('http://example.org/', 'bar')))
-        self.assertNotEqual(hash(ClosedNamespace('http://example.org/')), hash(Foo('http://example.org/')))
-        self.assertNotEqual(hash(Foo('http://example.org/')), hash(ClosedNamespace('http://example.org/')))
+        self.assertEqual(FinalNamespace('http://example.org'), FinalNamespace('http://example.org'))
+        self.assertEqual(hash(FinalNamespace('http://example.org')), hash(FinalNamespace('http://example.org')))
+        # FinalNamespace compares to string
+        self.assertEqual(FinalNamespace('http://example.org'), 'http://example.org')
+        self.assertEqual(hash(FinalNamespace('http://example.org')), hash('http://example.org'))
+        # URI must match
+        self.assertNotEqual(FinalNamespace('http://example.org'), FinalNamespace('http://example.com'))
+        self.assertNotEqual(hash(FinalNamespace('http://example.org')), hash(FinalNamespace('http://example.com')))
+        # separator is ignored
+        self.assertEqual(FinalNamespace('http://example.org'), FinalNamespace('http://example.org', sep='/'))
+        self.assertEqual(hash(FinalNamespace('http://example.org')), hash(FinalNamespace('http://example.org', sep='/')))
 
     def test_getattr(self):
-        self.assertEqual(ClosedNamespace('http://example.org/', 'foo', 'bar').foo, 'http://example.org#foo')
-        self.assertEqual(ClosedNamespace('http://example.org/', 'bar', 'bar').bar, 'http://example.org#bar')
-        self.assertEqual(ClosedNamespace('http://example.org/me#', 'foo', 'bar').foo, 'http://example.org/me#foo')
-        self.assertEqual(ClosedNamespace('http://example.org/me#', 'foo', 'bar').bar, 'http://example.org/me#bar')
-        self.assertRaises(KeyError, getattr, ClosedNamespace('http://example.org/', 'bar', 'bar'), 'foobar')
-        self.assertRaises(KeyError, getattr, ClosedNamespace('http://example.org#', 'bar', 'bar'), 'foobar')
-
-    def test_getitem(self):
-        self.assertEqual(ClosedNamespace('http://example.org/', 'foo', 'bar')['foo'], 'http://example.org#foo')
-        self.assertEqual(ClosedNamespace('http://example.org/', 'foo', 'bar')['bar'], 'http://example.org#bar')
-        self.assertEqual(ClosedNamespace('http://example.org/me#', 'foo', 'bar')['foo'], 'http://example.org/me#foo')
-        self.assertEqual(ClosedNamespace('http://example.org/me#', 'foo', 'bar')['bar'], 'http://example.org/me#bar')
-        self.assertRaises(KeyError, ClosedNamespace('http://example.org/', 'bar', 'bar').__getitem__, 'foobar')
-        self.assertRaises(KeyError, ClosedNamespace('http://example.org#', 'bar', 'bar').__getitem__, 'foobar')
+        self.assertEqual(FinalNamespace('http://example.org').foo, FinalNamespace('http://example.org#foo'))
+        self.assertEqual(FinalNamespace('http://example.org').bar, FinalNamespace('http://example.org#bar'))
+        self.assertEqual(FinalNamespace('http://example.org', sep='/').bar, FinalNamespace('http://example.org/bar'))
 
 
 ## main ##
diff --git a/test/query/ast_test/test_fetch.py b/test/query/ast_test/test_fetch.py
index 0c48a1f..ccb680e 100644
--- a/test/query/ast_test/test_fetch.py
+++ b/test/query/ast_test/test_fetch.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the tagit test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import unittest
 
diff --git a/test/query/ast_test/test_filter_.py b/test/query/ast_test/test_filter_.py
index 39b98f8..d0d42ea 100644
--- a/test/query/ast_test/test_filter_.py
+++ b/test/query/ast_test/test_filter_.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the tagit test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import unittest
 
@@ -387,7 +382,7 @@ class TestPredicate(unittest.TestCase):
         # member returns predicate
         # predicate must be an URI
         self.assertEqual(Predicate(ns.bse.filesize).predicate, ns.bse.filesize)
-        self.assertEqual(Predicate(URI('hello world')).predicate, URI('hello world'))
+        self.assertEqual(Predicate(URI('hello_world')).predicate, URI('hello_world'))
         self.assertRaises(TypeError, Predicate, 1234)
         self.assertRaises(TypeError, Predicate, FilterExpression())
         self.assertRaises(TypeError, Predicate, FilterExpression())
diff --git a/test/query/test_matcher.py b/test/query/test_matcher.py
index e830cf8..6b975b2 100644
--- a/test/query/test_matcher.py
+++ b/test/query/test_matcher.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the tagit test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import operator
 import unittest
diff --git a/test/query/test_validator.py b/test/query/test_validator.py
index fec3d23..418463e 100644
--- a/test/query/test_validator.py
+++ b/test/query/test_validator.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the tagit test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import unittest
 
@@ -19,26 +14,29 @@ from bsfs.query.validator import Filter, Fetch
 
 ## code ##
 
+ns.bse = ns.bsfs.Entity()
+
 class TestFilter(unittest.TestCase):
     def setUp(self):
         self.schema = _schema.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
 
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:URI rdfs:subClassOf bsfs:Literal .
 
             bsfs:Tag rdfs:subClassOf bsfs:Node .
             xsd:string rdfs:subClassOf bsfs:Literal .
-            bsfs:Number rdfs:subClassOf bsfs:Literal .
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array .
-            xsd:integer rdfs:subClassOf bsfs:Number .
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            <https://schema.bsfs.io/core/Literal/Array/Feature> rdfs:subClassOf bsl:Array .
+            xsd:integer rdfs:subClassOf bsl:Number .
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
+            bsfs:Colors rdfs:subClassOf <https://schema.bsfs.io/core/Literal/Array/Feature> ;
                 bsfs:dimension "5"^^xsd:integer ;
                 bsfs:dtype bsfs:f32 .
 
@@ -75,7 +73,7 @@ class TestFilter(unittest.TestCase):
             ''')
         self.validate = Filter(self.schema)
 
-    def test_call(self):
+    def test_call(self): # tests validate implicitly
         # root_type must be a _schema.Node
         self.assertRaises(TypeError, self.validate, 1234, None)
         self.assertRaises(TypeError, self.validate, '1234', None)
@@ -272,10 +270,10 @@ class TestFilter(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, self.validate._distance, self.schema.node(ns.bsfs.Node),
             ast.filter.Distance([1,2,3], 1, False))
         # type must be a feature
-        self.assertRaises(errors.ConsistencyError, self.validate._distance, self.schema.literal(ns.bsfs.Array),
+        self.assertRaises(errors.ConsistencyError, self.validate._distance, self.schema.literal(ns.bsl.Array),
             ast.filter.Distance([1,2,3], 1, False))
         # type must be in the schema
-        self.assertRaises(errors.ConsistencyError, self.validate._distance, self.schema.literal(ns.bsfs.Feature).child(ns.bsfs.Invalid),
+        self.assertRaises(errors.ConsistencyError, self.validate._distance, self.schema.literal(ns.bsl.Array.Feature).child(ns.bsfs.Invalid),
             ast.filter.Distance([1,2,3], 1, False))
         # FIXME: reference must be a numpy array
         # reference must have the correct dimension
@@ -292,8 +290,8 @@ class TestFetch(unittest.TestCase):
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
 
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Tag rdfs:subClassOf bsfs:Node .
@@ -314,7 +312,7 @@ class TestFetch(unittest.TestCase):
             ''')
         self.validate = Fetch(self.schema)
 
-    def test_call(self):
+    def test_call(self): # tests validate implicitly
         # call accepts correct expressions
         self.assertTrue(self.validate(self.schema.node(ns.bsfs.Entity),
             ast.fetch.Fetch(ns.bse.tag, ast.fetch.Value(ns.bse.label, 'value'))))
diff --git a/test/schema/test_schema.py b/test/schema/test_schema.py
index 414e542..f52cf95 100644
--- a/test/schema/test_schema.py
+++ b/test/schema/test_schema.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the tagit test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import operator
 import unittest
@@ -19,6 +14,8 @@ from bsfs.schema.schema import Schema
 
 ## code ##
 
+ns.bse = ns.bsfs.Entity()
+
 class TestSchema(unittest.TestCase):
 
     def setUp(self):
@@ -26,8 +23,9 @@ class TestSchema(unittest.TestCase):
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
 
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Tag rdfs:subClassOf bsfs:Node .
@@ -36,7 +34,7 @@ class TestSchema(unittest.TestCase):
 
             xsd:string rdfs:subClassOf bsfs:Literal .
             bsfs:Number rdfs:subClassOf bsfs:Literal .
-            xsd:integer rdfs:subClassOf bsfs:Number .
+            xsd:integer rdfs:subClassOf bsl:Number .
             xsd:boolean rdfs:subClassOf bsfs:Literal .
 
             bse:tag rdfs:subClassOf bsfs:Predicate ;
@@ -179,13 +177,13 @@ class TestSchema(unittest.TestCase):
         self.assertEqual(str(Schema(self.predicates, self.nodes, self.literals)), 'Schema()')
         # repr conversion with only default nodes, literals, and predicates
         n = [ns.bsfs.Node]
-        l = [ns.bsfs.Array, ns.bsfs.BinaryBlob, ns.bsfs.Feature, ns.bsfs.Literal, ns.bsfs.Number, ns.bsfs.Time]
+        l = [ns.bsfs.Literal, ns.bsl.Array, ns.bsl.Array.Feature, ns.bsl.BinaryBlob, ns.bsl.Number, ns.bsl.Time]
         p = [ns.bsfs.Predicate]
         self.assertEqual(repr(Schema()), f'Schema({n}, {l}, {p})')
         self.assertEqual(repr(Schema([], [], [])), f'Schema({n}, {l}, {p})')
         # repr conversion
         n = [ns.bsfs.Entity, ns.bsfs.Image, ns.bsfs.Node, ns.bsfs.Tag, ns.bsfs.Unused]
-        l = [ns.bsfs.Array, ns.bsfs.BinaryBlob, ns.bsfs.Feature, ns.bsfs.Literal, ns.bsfs.Number, ns.bsfs.Time, ns.xsd.boolean, ns.xsd.integer, ns.xsd.string]
+        l = [ns.xsd.boolean, ns.xsd.integer, ns.xsd.string, ns.bsfs.Literal, ns.bsl.Array, ns.bsl.Array.Feature, ns.bsl.BinaryBlob, ns.bsl.Number, ns.bsl.Time]
         p = [ns.bse.comment, ns.bse.group, ns.bse.tag, ns.bsfs.Predicate]
         self.assertEqual(repr(Schema(self.predicates, self.nodes, self.literals)), f'Schema({n}, {l}, {p})')
 
diff --git a/test/schema/test_serialize.py b/test/schema/test_serialize.py
index fc6b20a..7d5d3ae 100644
--- a/test/schema/test_serialize.py
+++ b/test/schema/test_serialize.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the tagit test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import re
 import unittest
@@ -19,6 +14,8 @@ from bsfs.schema.serialize import from_string, to_string
 
 ## code ##
 
+ns.bse = ns.bsfs.Entity()
+
 class TestFromString(unittest.TestCase):
 
     def test_empty(self):
@@ -30,7 +27,7 @@ class TestFromString(unittest.TestCase):
         # must not have circular dependencies
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bsfs: <https://schema.bsfs.io/core/>
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             # ah, a nice circular dependency
             bsfs:Entity rdfs:subClassOf bsfs:Document .
@@ -44,8 +41,8 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             xsd:string rdfs:subClassOf bsfs:Literal .
 
@@ -59,7 +56,7 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bsfs: <https://schema.bsfs.io/core/>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Document rdfs:subClassOf bsfs:Node .
@@ -71,8 +68,8 @@ class TestFromString(unittest.TestCase):
         self.assertEqual(Schema({}, {n_unused}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:unused rdfs:subClassOf bsfs:Node . # unused symbol
             '''))
@@ -85,8 +82,8 @@ class TestFromString(unittest.TestCase):
         self.assertEqual(Schema({}, {n_ent, n_tag, n_doc, n_image}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             # nodes inherit from same parent
             bsfs:Entity rdfs:subClassOf bsfs:Node .
@@ -105,8 +102,8 @@ class TestFromString(unittest.TestCase):
         self.assertEqual(Schema({p_filename}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             xsd:string rdfs:subClassOf bsfs:Literal .
@@ -121,7 +118,7 @@ class TestFromString(unittest.TestCase):
         self.assertDictEqual(from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bsfs: <https://schema.bsfs.io/core/>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
 
@@ -129,7 +126,7 @@ class TestFromString(unittest.TestCase):
         self.assertDictEqual(from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bsfs: <https://schema.bsfs.io/core/>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node ;
                 rdfs:label "hello world"^^xsd:string ;
@@ -146,8 +143,8 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
 
@@ -161,7 +158,7 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bsfs: <https://schema.bsfs.io/core/>
 
             xsd:string rdfs:subClassOf bsfs:Literal .
             xsd:name rdfs:subClassOf bsfs:Literal .
@@ -173,8 +170,8 @@ class TestFromString(unittest.TestCase):
         self.assertEqual(Schema({}, {}, {l_unused}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             xsd:unused rdfs:subClassOf bsfs:Literal . # unused symbol
             '''))
@@ -187,13 +184,14 @@ class TestFromString(unittest.TestCase):
         self.assertEqual(Schema({}, {}, {l_string, l_integer, l_unsigned, l_signed}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
 
             # literals inherit from same parent
             xsd:string rdfs:subClassOf bsfs:Literal .
-            bsfs:Number rdfs:subClassOf bsfs:Literal .
-            xsd:integer rdfs:subClassOf bsfs:Number .
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsl:Number .
 
             # literals inherit from same parent
             xsd:unsigned rdfs:subClassOf xsd:integer .
@@ -208,8 +206,8 @@ class TestFromString(unittest.TestCase):
         self.assertEqual(Schema({p_filename}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             xsd:string rdfs:subClassOf bsfs:Literal .
@@ -224,7 +222,7 @@ class TestFromString(unittest.TestCase):
         self.assertDictEqual(from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bsfs: <https://schema.bsfs.io/core/>
 
             xsd:string rdfs:subClassOf bsfs:Literal .
 
@@ -232,7 +230,7 @@ class TestFromString(unittest.TestCase):
         self.assertDictEqual(from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bsfs: <https://schema.bsfs.io/core/>
 
             xsd:string rdfs:subClassOf bsfs:Literal ;
                 rdfs:label "hello world"^^xsd:string ;
@@ -249,8 +247,8 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             xsd:string rdfs:subClassOf bsfs:Literal .
 
@@ -263,8 +261,8 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Literal .
             xsd:string rdfs:subClassOf bsfs:Literal .
@@ -279,8 +277,8 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
 
@@ -293,8 +291,8 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
 
@@ -307,8 +305,8 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
 
@@ -325,8 +323,8 @@ class TestFromString(unittest.TestCase):
         self.assertEqual(Schema({p_comment}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             xsd:string rdfs:subClassOf bsfs:Literal .
@@ -345,8 +343,8 @@ class TestFromString(unittest.TestCase):
         self.assertEqual(Schema({p_comment}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             xsd:string rdfs:subClassOf bsfs:Literal .
@@ -367,8 +365,8 @@ class TestFromString(unittest.TestCase):
         self.assertEqual(Schema({p_comment}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             xsd:string rdfs:subClassOf bsfs:Literal .
@@ -388,8 +386,8 @@ class TestFromString(unittest.TestCase):
         self.assertEqual(Schema({p_foo}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
 
@@ -410,8 +408,8 @@ class TestFromString(unittest.TestCase):
         self.assertEqual(Schema({p_foobar}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Image rdfs:subClassOf bsfs:Entity .
@@ -426,8 +424,8 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Image rdfs:subClassOf bsfs:Entity .
@@ -449,8 +447,8 @@ class TestFromString(unittest.TestCase):
         self.assertEqual(Schema({p_foobar}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Image rdfs:subClassOf bsfs:Entity .
@@ -465,8 +463,8 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Image rdfs:subClassOf bsfs:Entity .
@@ -483,8 +481,8 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Annotation rdfs:subClassOf bsfs:Predicate .
@@ -504,8 +502,8 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
 
@@ -521,8 +519,8 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
 
@@ -538,8 +536,8 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
 
@@ -556,8 +554,8 @@ class TestFromString(unittest.TestCase):
         self.assertDictEqual(from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bse:comment rdfs:subClassOf bsfs:Predicate ;
                 rdfs:range bsfs:Node .
@@ -566,8 +564,8 @@ class TestFromString(unittest.TestCase):
         self.assertDictEqual(from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bse:comment rdfs:subClassOf bsfs:Predicate ;
                 rdfs:range bsfs:Node ;
@@ -586,70 +584,78 @@ class TestFromString(unittest.TestCase):
         self.assertEqual(Schema(literals={f_colors}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsa: <https://schema.bsfs.io/core/Literal/Array/>
 
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array.
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            bsa:Feature rdfs:subClassOf bsl:Array.
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature .
+            bsfs:Colors rdfs:subClassOf bsa:Feature .
 
             '''))
 
         # features inherit properties from parents
-        f_colors = types.ROOT_FEATURE.child(ns.bsfs.Colors, dimension=1234, dtype=ns.bsfs.i32)
-        f_main_colors = f_colors.child(ns.bsfs.MainColor, distance=ns.bsfs.cosine, dtype=ns.bsfs.f16)
+        f_colors = types.ROOT_FEATURE.child(ns.bsfs.Colors, dimension=1234, dtype=ns.bsfs.dtype().i32)
+        f_main_colors = f_colors.child(ns.bsfs.MainColor, distance=ns.bsfs.cosine, dtype=ns.bsfs.dtype().f16)
         self.assertEqual(Schema(literals={f_colors, f_main_colors}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsa: <https://schema.bsfs.io/core/Literal/Array/>
 
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array.
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            bsa:Feature rdfs:subClassOf bsl:Array.
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ; # inherits distance from bsfs:Feature
-                bsfs:dimension "1234"^^xsd:integer ; # overwrites bsfs:Feature
-                bsfs:dtype bsfs:i32 . # overwrites bsfs:Feature
+            bsfs:Colors rdfs:subClassOf bsa:Feature ; # inherits distance from bsa:Feature
+                bsfs:dimension "1234"^^xsd:integer ; # overwrites bsa:Feature
+                bsfs:dtype <https://schema.bsfs.io/core/dtype#i32> . # overwrites bsa:Feature
 
             bsfs:MainColor rdfs:subClassOf bsfs:Colors ; # inherits dimension from bsfs:Colors
-                bsfs:distance bsfs:cosine ; # overwrites bsfs:Feature
-                bsfs:dtype bsfs:f16 . # overwrites bsfs:Colors
+                bsfs:distance bsfs:cosine ; # overwrites bsa:Feature
+                bsfs:dtype <https://schema.bsfs.io/core/dtype#f16> . # overwrites bsfs:Colors
 
             '''))
 
         # feature definition can be split across multiple statements.
         # statements can be repeated
-        f_colors = types.ROOT_FEATURE.child(ns.bsfs.Colors, dimension=1234, dtype=ns.bsfs.f32)
+        f_colors = types.ROOT_FEATURE.child(ns.bsfs.Colors, dimension=1234, dtype=ns.bsfs.dtype().f32)
         self.assertEqual(Schema(literals={f_colors}), from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsa: <https://schema.bsfs.io/core/Literal/Array/>
 
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array.
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            bsa:Feature rdfs:subClassOf bsl:Array.
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
+            bsfs:Colors rdfs:subClassOf bsa:Feature ;
                 bsfs:dimension "1234"^^xsd:integer .
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
+            bsfs:Colors rdfs:subClassOf bsa:Feature ;
                 bsfs:dimension "1234"^^xsd:integer ; # non-conflicting repetition
-                bsfs:dtype bsfs:f32 .
+                bsfs:dtype <https://schema.bsfs.io/core/dtype#f32> .
             '''))
 
         # cannot define the same feature from multiple parents
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsa: <https://schema.bsfs.io/core/Literal/Array/>
 
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array.
-            bsfs:ColorSpace rdfs:subClassOf bsfs:Feature .
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            bsa:Feature rdfs:subClassOf bsl:Array.
+            bsfs:ColorSpace rdfs:subClassOf bsa:Feature .
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature .
+            bsfs:Colors rdfs:subClassOf bsa:Feature .
             bsfs:Colors rdfs:subClassOf bsfs:ColorSpace .
 
             ''')
@@ -657,16 +663,18 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsa: <https://schema.bsfs.io/core/Literal/Array/>
 
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array.
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            bsa:Feature rdfs:subClassOf bsl:Array.
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
+            bsfs:Colors rdfs:subClassOf bsa:Feature ;
                 bsfs:dimension "1234"^^xsd:integer .
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
+            bsfs:Colors rdfs:subClassOf bsa:Feature ;
                 bsfs:dimension "4321"^^xsd:integer . # conflicting dimension
 
             ''')
@@ -674,32 +682,36 @@ class TestFromString(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsa: <https://schema.bsfs.io/core/Literal/Array/>
 
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array.
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            bsa:Feature rdfs:subClassOf bsl:Array.
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
-                bsfs:dtype bsfs:f32 .
+            bsfs:Colors rdfs:subClassOf bsa:Feature ;
+                bsfs:dtype <https://schema.bsfs.io/core/dtype#i32> .
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
-                bsfs:dtype bsfs:f16 . # conflicting dtype
+            bsfs:Colors rdfs:subClassOf bsa:Feature ;
+                bsfs:dtype <https://schema.bsfs.io/core/dtype#f16> .  # conflicting dtype
             ''')
         # cannot assign multiple conflicting distance metrics to the same feature
         self.assertRaises(errors.ConsistencyError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsa: <https://schema.bsfs.io/core/Literal/Array/>
 
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array.
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            bsa:Feature rdfs:subClassOf bsl:Array.
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
+            bsfs:Colors rdfs:subClassOf bsa:Feature ;
                 bsfs:distance bsfs:euclidean .
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
+            bsfs:Colors rdfs:subClassOf bsa:Feature ;
                 bsfs:distance bsfs:cosine . # conflicting distance
             ''')
 
@@ -707,26 +719,30 @@ class TestFromString(unittest.TestCase):
         self.assertDictEqual(from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsa: <https://schema.bsfs.io/core/Literal/Array/>
 
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array.
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            bsa:Feature rdfs:subClassOf bsl:Array.
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
+            bsfs:Colors rdfs:subClassOf bsa:Feature ;
                 bsfs:dimension "1234"^^xsd:integer .
 
             ''').literal(ns.bsfs.Colors).annotations, {})
         self.assertDictEqual(from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsa: <https://schema.bsfs.io/core/Literal/Array/>
 
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array.
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            bsa:Feature rdfs:subClassOf bsl:Array.
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
+            bsfs:Colors rdfs:subClassOf bsa:Feature ;
                 bsfs:dimension "1234"^^xsd:integer ;
                 rdfs:label "hello world"^^xsd:string ;
                 bsfs:foo "1234"^^xsd:integer .
@@ -753,10 +769,10 @@ class TestFromString(unittest.TestCase):
         p_group = p_tag.child(ns.bse.group, domain=n_image, unique=True)
         p_comment = p_annotation.child(ns.bse.comment, range=l_string)
         # features
-        f_colors = types.ROOT_FEATURE.child(URI('http://bsfs.ai/schema/Feature/colors_spatial'),
-            dtype=ns.bsfs.f16, distance=ns.bsfs.euclidean)
-        f_colors1234 = f_colors.child(URI('http://bsfs.ai/schema/Feature/colors_spatial#1234'), dimension=1024)
-        f_colors4321 = f_colors.child(URI('http://bsfs.ai/schema/Feature/colors_spatial#4321'), dimension=2048)
+        f_colors = types.ROOT_FEATURE.child(URI('https://schema.bsfs.io/core/Feature/colors_spatial'),
+            dtype=ns.bsfs.dtype().f16, distance=ns.bsfs.euclidean)
+        f_colors1234 = f_colors.child(URI('https://schema.bsfs.io/core/Feature/colors_spatial#1234'), dimension=1024)
+        f_colors4321 = f_colors.child(URI('https://schema.bsfs.io/core/Feature/colors_spatial#4321'), dimension=2048)
         # schema
         ref = Schema(
             {p_annotation, p_tag, p_group, p_comment},
@@ -769,8 +785,10 @@ class TestFromString(unittest.TestCase):
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
 
             # bsfs prefixes
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsa: <https://schema.bsfs.io/core/Literal/Array/>
 
             # nodes
             bsfs:Entity rdfs:subClassOf bsfs:Node ;
@@ -782,10 +800,10 @@ class TestFromString(unittest.TestCase):
             # literals
             xsd:string rdfs:subClassOf bsfs:Literal ;
                 rdfs:label "A sequence of characters"^^xsd:string .
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array.
-            bsfs:Number rdfs:subClassOf bsfs:Literal .
-            xsd:integer rdfs:subClassOf bsfs:Number .
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            bsa:Feature rdfs:subClassOf bsl:Array.
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsl:Number .
             xsd:boolean rdfs:subClassOf bsfs:Literal .
 
 
@@ -794,19 +812,19 @@ class TestFromString(unittest.TestCase):
                 rdfs:label "node annotation"^^xsd:string .
 
             # feature instances
-            <http://bsfs.ai/schema/Feature/colors_spatial> rdfs:subClassOf bsfs:Feature ;
-                bsfs:dtype bsfs:f16 ;
+            <https://schema.bsfs.io/core/Feature/colors_spatial> rdfs:subClassOf bsa:Feature ;
+                bsfs:dtype <https://schema.bsfs.io/core/dtype#f16> ;
                 bsfs:distance bsfs:euclidean ;
                 # annotations
                 rdfs:label "ColorsSpatial instances. Dimension depends on instance."^^xsd:string ;
                 bsfs:first_arg "1234"^^xsd:integer ;
                 bsfs:second_arg "hello world"^^xsd:string .
 
-            <http://bsfs.ai/schema/Feature/colors_spatial#1234> rdfs:subClassOf <http://bsfs.ai/schema/Feature/colors_spatial> ;
+            <https://schema.bsfs.io/core/Feature/colors_spatial#1234> rdfs:subClassOf <https://schema.bsfs.io/core/Feature/colors_spatial> ;
                 bsfs:dimension "1024"^^xsd:integer ;
                 rdfs:label "Main colors spatial instance"^^xsd:string .
 
-            <http://bsfs.ai/schema/Feature/colors_spatial#4321> rdfs:subClassOf <http://bsfs.ai/schema/Feature/colors_spatial> ;
+            <https://schema.bsfs.io/core/Feature/colors_spatial#4321> rdfs:subClassOf <https://schema.bsfs.io/core/Feature/colors_spatial> ;
                 bsfs:dimension "2048"^^xsd:integer .
 
             # predicate instances
@@ -834,19 +852,19 @@ class TestFromString(unittest.TestCase):
         self.assertDictEqual(gen.node(ns.bsfs.Tag).annotations, {ns.rdfs.label: 'Tag'})
         self.assertDictEqual(gen.literal(ns.xsd.string).annotations, {ns.rdfs.label: 'A sequence of characters'})
         self.assertDictEqual(gen.predicate(ns.bsfs.Annotation).annotations, {ns.rdfs.label: 'node annotation'})
-        self.assertDictEqual(gen.literal(URI('http://bsfs.ai/schema/Feature/colors_spatial')).annotations, {
+        self.assertDictEqual(gen.literal(URI('https://schema.bsfs.io/core/Feature/colors_spatial')).annotations, {
             ns.rdfs.label: 'ColorsSpatial instances. Dimension depends on instance.',
             ns.bsfs.first_arg: 1234,
             ns.bsfs.second_arg: 'hello world',
             })
-        self.assertDictEqual(gen.literal(URI('http://bsfs.ai/schema/Feature/colors_spatial#1234')).annotations, {
+        self.assertDictEqual(gen.literal(URI('https://schema.bsfs.io/core/Feature/colors_spatial#1234')).annotations, {
             ns.rdfs.label: 'Main colors spatial instance'})
         self.assertDictEqual(gen.predicate(ns.bse.tag).annotations, {ns.rdfs.label: 'connect entity to a tag'})
 
         # blank nodes result in an error
         self.assertRaises(errors.BackendError, from_string, '''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bsfs: <https://schema.bsfs.io/core/>
             bsfs:Entity rdfs:subClassOf bsfs:Node ;
                 bsfs:foo _:bar .
             ''')
@@ -981,29 +999,29 @@ class TestToString(unittest.TestCase):
 
     def test_feature(self):
         # root features
-        f_colors = types.ROOT_FEATURE.child(URI('http://bsfs.ai/schema/Feature/colors'),
+        f_colors = types.ROOT_FEATURE.child(URI('https://schema.bsfs.io/core/Feature/colors'),
             distance=ns.bsfs.cosine)
         # derived features
-        f_colors1234 = f_colors.child(URI('http://bsfs.ai/schema/Feature/colors#1234'),
+        f_colors1234 = f_colors.child(URI('https://schema.bsfs.io/core/Feature/colors#1234'),
             dimension=1024) # inherits dtype, distance
-        f_colors4321 = f_colors.child(URI('http://bsfs.ai/schema/Feature/colors#4321'),
+        f_colors4321 = f_colors.child(URI('https://schema.bsfs.io/core/Feature/colors#4321'),
             dimension=2048, distance=ns.bsfs.euclidean) # inherits dtype
         # create schema
         schema = Schema(literals={f_colors, f_colors1234, f_colors4321})
 
         schema_str = to_string(schema)
         # all symbols are serialized
-        self.assertIn('bsfs:Array', schema_str)
-        self.assertIn('<http://bsfs.ai/schema/Feature/colors', schema_str)
-        self.assertIn('<http://bsfs.ai/schema/Feature/colors#1234', schema_str)
-        self.assertIn('<http://bsfs.ai/schema/Feature/colors#4321', schema_str)
+        self.assertIn('bsl:Array', schema_str)
+        self.assertIn('<https://schema.bsfs.io/core/Feature/colors', schema_str)
+        self.assertIn('<https://schema.bsfs.io/core/Feature/colors#1234', schema_str)
+        self.assertIn('<https://schema.bsfs.io/core/Feature/colors#4321', schema_str)
         # inherited properties are not serialized
-        self.assertIsNotNone(re.search(r'<http://bsfs\.ai/schema/Feature/colors#1234>[^\.]*bsfs:dimension[^\.]', schema_str))
-        self.assertIsNone(re.search(r'<http://bsfs\.ai/schema/Feature/colors#1234>[^\.]*bsfs:dtype[^\.]', schema_str))
-        self.assertIsNone(re.search(r'<http://bsfs\.ai/schema/Feature/colors#1234>[^\.]*bsfs:distance[^\.]', schema_str))
-        self.assertIsNotNone(re.search(r'<http://bsfs\.ai/schema/Feature/colors#4321>[^\.]*bsfs:dimension[^\.]', schema_str))
-        self.assertIsNotNone(re.search(r'<http://bsfs\.ai/schema/Feature/colors#4321>[^\.]*bsfs:distance[^\.]', schema_str))
-        self.assertIsNone(re.search(r'<http://bsfs\.ai/schema/Feature/colors#4321>[^\.]*bsfs:dtype[^\.]', schema_str))
+        self.assertIsNotNone(re.search(r'<https://schema.bsfs\.io/core/Feature/colors#1234>.*[^\.]*bsfs:dimension[^\.]', schema_str))
+        self.assertIsNone(re.search(r'<https://schema\.bsfs\.io/core/Feature/colors#1234>.*[^\.]*bsfs:dtype[^\.]', schema_str))
+        self.assertIsNone(re.search(r'<https://schema\.bsfs\.io/core/Feature/colors#1234>.*[^\.]*bsfs:distance[^\.]', schema_str))
+        self.assertIsNotNone(re.search(r'<https://schema\.bsfs\.io/core/Feature/colors#4321>.*[^\.]*bsfs:dimension[^\.]', schema_str))
+        self.assertIsNotNone(re.search(r'<https://schema\.bsfs\.io/core/Feature/colors#4321>.*[^\.]*bsfs:distance[^\.]', schema_str))
+        self.assertIsNone(re.search(r'<https://schema\.bsfs\.io/core/Feature/colors#4321>.*[^\.]*bsfs:dtype[^\.]', schema_str))
         # unserialize yields the original schema
         self.assertEqual(schema, from_string(schema_str))
 
@@ -1014,12 +1032,12 @@ class TestToString(unittest.TestCase):
             ns.bsfs.foo: 1234,
             ns.bsfs.bar: False,
             }
-        f_colors = types.ROOT_FEATURE.child(URI('http://bsfs.ai/schema/Feature/colors'),
-            dtype=ns.bsfs.f16, distance=ns.bsfs.euclidean,
+        f_colors = types.ROOT_FEATURE.child(URI('https://schema.bsfs.io/core/Feature/colors'),
+            dtype=ns.bsfs.dtype().f16, distance=ns.bsfs.euclidean,
             **annotations)
         self.assertDictEqual(
             annotations,
-            from_string(to_string(Schema(literals={f_colors}))).literal(URI('http://bsfs.ai/schema/Feature/colors')).annotations)
+            from_string(to_string(Schema(literals={f_colors}))).literal(URI('https://schema.bsfs.io/core/Feature/colors')).annotations)
 
 
 ## main ##
diff --git a/test/schema/test_types.py b/test/schema/test_types.py
index c5895d2..9bfa8c5 100644
--- a/test/schema/test_types.py
+++ b/test/schema/test_types.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the tagit test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import operator
 import unittest
@@ -19,6 +14,8 @@ from bsfs.schema.types import _Type, Vertex, Node, Literal, Predicate, Feature
 
 ## code ##
 
+ns.bse = ns.bsfs.Entity()
+
 class TestType(unittest.TestCase):
 
     def test_parents(self):
diff --git a/test/triple_store/sparql/test_distance.py b/test/triple_store/sparql/test_distance.py
index 0659459..e95be5a 100644
--- a/test/triple_store/sparql/test_distance.py
+++ b/test/triple_store/sparql/test_distance.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import numpy as np
 import unittest
diff --git a/test/triple_store/sparql/test_parse_fetch.py b/test/triple_store/sparql/test_parse_fetch.py
index 0961789..1d793e7 100644
--- a/test/triple_store/sparql/test_parse_fetch.py
+++ b/test/triple_store/sparql/test_parse_fetch.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import rdflib
 import unittest
@@ -20,10 +15,9 @@ from bsfs.triple_store.sparql.parse_fetch import Fetch
 
 ## code ##
 
-bsfs = Namespace('http://bsfs.ai/schema', fsep='/')
-bse = Namespace('http://bsfs.ai/schema/Entity')
-bst = Namespace('http://bsfs.ai/schema/Tag')
-bsc = Namespace('http://bsfs.ai/schema/Collection')
+ns.bse = ns.bsfs.Entity()
+ns.bst = ns.bsfs.Tag()
+ns.bsc = ns.bsfs.Collection()
 
 class TestParseFetch(unittest.TestCase):
 
@@ -32,10 +26,10 @@ class TestParseFetch(unittest.TestCase):
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
 
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
-            prefix bst: <http://bsfs.ai/schema/Tag#>
-            prefix bsc: <http://bsfs.ai/schema/Collection#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bst: <https://schema.bsfs.io/core/Tag#>
+            prefix bsc: <https://schema.bsfs.io/core/Collection#>
 
             # nodes
             bsfs:Entity rdfs:subClassOf bsfs:Node .
@@ -88,43 +82,43 @@ class TestParseFetch(unittest.TestCase):
         # graph to test queries
         self.graph = rdflib.Graph()
         # schema hierarchies
-        self.graph.add((rdflib.URIRef('http://bsfs.ai/schema/Entity'), rdflib.RDFS.subClassOf, rdflib.URIRef('http://bsfs.ai/schema/Node')))
-        self.graph.add((rdflib.URIRef('http://bsfs.ai/schema/Collection'), rdflib.RDFS.subClassOf, rdflib.URIRef('http://bsfs.ai/schema/Node')))
-        self.graph.add((rdflib.URIRef('http://bsfs.ai/schema/Tag'), rdflib.RDFS.subClassOf, rdflib.URIRef('http://bsfs.ai/schema/Node')))
+        self.graph.add((rdflib.URIRef('https://schema.bsfs.io/core/Entity'), rdflib.RDFS.subClassOf, rdflib.URIRef('https://schema.bsfs.io/core/Node')))
+        self.graph.add((rdflib.URIRef('https://schema.bsfs.io/core/Collection'), rdflib.RDFS.subClassOf, rdflib.URIRef('https://schema.bsfs.io/core/Node')))
+        self.graph.add((rdflib.URIRef('https://schema.bsfs.io/core/Tag'), rdflib.RDFS.subClassOf, rdflib.URIRef('https://schema.bsfs.io/core/Node')))
         # entities
-        self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')))
-        self.graph.add((rdflib.URIRef('http://example.com/entity#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')))
+        self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')))
+        self.graph.add((rdflib.URIRef('http://example.com/entity#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')))
         # tags
-        self.graph.add((rdflib.URIRef('http://example.com/tag#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Tag')))
-        self.graph.add((rdflib.URIRef('http://example.com/tag#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Tag')))
+        self.graph.add((rdflib.URIRef('http://example.com/tag#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Tag')))
+        self.graph.add((rdflib.URIRef('http://example.com/tag#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Tag')))
         # collections
-        self.graph.add((rdflib.URIRef('http://example.com/collection#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Collection')))
-        self.graph.add((rdflib.URIRef('http://example.com/collection#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Collection')))
+        self.graph.add((rdflib.URIRef('http://example.com/collection#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Collection')))
+        self.graph.add((rdflib.URIRef('http://example.com/collection#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Collection')))
         # entity literals
-        self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef(bse.rank), rdflib.Literal('1234', datatype=rdflib.XSD.integer)))
-        self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef(bse.filename), rdflib.Literal('filename_1234', datatype=rdflib.XSD.string)))
-        #self.graph.add((rdflib.URIRef('http://example.com/entity#4321'), rdflib.URIRef(bse.rank), rdflib.Literal('4321', datatype=rdflib.XSD.integer)))
-        self.graph.add((rdflib.URIRef('http://example.com/entity#4321'), rdflib.URIRef(bse.filename), rdflib.Literal('filename_4321', datatype=rdflib.XSD.string)))
+        self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef(ns.bse.rank), rdflib.Literal('1234', datatype=rdflib.XSD.integer)))
+        self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef(ns.bse.filename), rdflib.Literal('filename_1234', datatype=rdflib.XSD.string)))
+        #self.graph.add((rdflib.URIRef('http://example.com/entity#4321'), rdflib.URIRef(ns.bse.rank), rdflib.Literal('4321', datatype=rdflib.XSD.integer)))
+        self.graph.add((rdflib.URIRef('http://example.com/entity#4321'), rdflib.URIRef(ns.bse.filename), rdflib.Literal('filename_4321', datatype=rdflib.XSD.string)))
         # tag literals
-        self.graph.add((rdflib.URIRef('http://example.com/tag#1234'), rdflib.URIRef(bst.label), rdflib.Literal('tag_label_1234', datatype=rdflib.XSD.string)))
-        self.graph.add((rdflib.URIRef('http://example.com/tag#4321'), rdflib.URIRef(bst.label), rdflib.Literal('tag_label_4321', datatype=rdflib.XSD.string)))
+        self.graph.add((rdflib.URIRef('http://example.com/tag#1234'), rdflib.URIRef(ns.bst.label), rdflib.Literal('tag_label_1234', datatype=rdflib.XSD.string)))
+        self.graph.add((rdflib.URIRef('http://example.com/tag#4321'), rdflib.URIRef(ns.bst.label), rdflib.Literal('tag_label_4321', datatype=rdflib.XSD.string)))
         # collection literals
-        self.graph.add((rdflib.URIRef('http://example.com/collection#1234'), rdflib.URIRef(bsc.label), rdflib.Literal('collection_label_1234', datatype=rdflib.XSD.string)))
-        self.graph.add((rdflib.URIRef('http://example.com/collection#1234'), rdflib.URIRef(bsc.rating), rdflib.Literal('1234', datatype=rdflib.XSD.integer)))
-        self.graph.add((rdflib.URIRef('http://example.com/collection#4321'), rdflib.URIRef(bsc.label), rdflib.Literal('collection_label_4321', datatype=rdflib.XSD.string)))
-        self.graph.add((rdflib.URIRef('http://example.com/collection#4321'), rdflib.URIRef(bsc.rating), rdflib.Literal('4321', datatype=rdflib.XSD.integer)))
+        self.graph.add((rdflib.URIRef('http://example.com/collection#1234'), rdflib.URIRef(ns.bsc.label), rdflib.Literal('collection_label_1234', datatype=rdflib.XSD.string)))
+        self.graph.add((rdflib.URIRef('http://example.com/collection#1234'), rdflib.URIRef(ns.bsc.rating), rdflib.Literal('1234', datatype=rdflib.XSD.integer)))
+        self.graph.add((rdflib.URIRef('http://example.com/collection#4321'), rdflib.URIRef(ns.bsc.label), rdflib.Literal('collection_label_4321', datatype=rdflib.XSD.string)))
+        self.graph.add((rdflib.URIRef('http://example.com/collection#4321'), rdflib.URIRef(ns.bsc.rating), rdflib.Literal('4321', datatype=rdflib.XSD.integer)))
         # entity-tag links
-        self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef(bse.tag), rdflib.URIRef('http://example.com/tag#1234')))
-        self.graph.add((rdflib.URIRef('http://example.com/entity#4321'), rdflib.URIRef(bse.tag), rdflib.URIRef('http://example.com/tag#4321')))
+        self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef(ns.bse.tag), rdflib.URIRef('http://example.com/tag#1234')))
+        self.graph.add((rdflib.URIRef('http://example.com/entity#4321'), rdflib.URIRef(ns.bse.tag), rdflib.URIRef('http://example.com/tag#4321')))
         # entity-collection links
-        self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef(bse.collection), rdflib.URIRef('http://example.com/collection#1234')))
-        self.graph.add((rdflib.URIRef('http://example.com/entity#4321'), rdflib.URIRef(bse.collection), rdflib.URIRef('http://example.com/collection#4321')))
+        self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef(ns.bse.collection), rdflib.URIRef('http://example.com/collection#1234')))
+        self.graph.add((rdflib.URIRef('http://example.com/entity#4321'), rdflib.URIRef(ns.bse.collection), rdflib.URIRef('http://example.com/collection#4321')))
         # collection-tag links
-        self.graph.add((rdflib.URIRef('http://example.com/collection#1234'), rdflib.URIRef(bsc.tag), rdflib.URIRef('http://example.com/tag#1234')))
-        self.graph.add((rdflib.URIRef('http://example.com/collection#4321'), rdflib.URIRef(bsc.tag), rdflib.URIRef('http://example.com/tag#4321')))
+        self.graph.add((rdflib.URIRef('http://example.com/collection#1234'), rdflib.URIRef(ns.bsc.tag), rdflib.URIRef('http://example.com/tag#1234')))
+        self.graph.add((rdflib.URIRef('http://example.com/collection#4321'), rdflib.URIRef(ns.bsc.tag), rdflib.URIRef('http://example.com/tag#4321')))
         # tag-entity links # NOTE: cross-over
-        self.graph.add((rdflib.URIRef('http://example.com/tag#1234'), rdflib.URIRef(bst.main), rdflib.URIRef('http://example.com/entity#4321')))
-        self.graph.add((rdflib.URIRef('http://example.com/tag#4321'), rdflib.URIRef(bst.main), rdflib.URIRef('http://example.com/entity#1234')))
+        self.graph.add((rdflib.URIRef('http://example.com/tag#1234'), rdflib.URIRef(ns.bst.main), rdflib.URIRef('http://example.com/entity#4321')))
+        self.graph.add((rdflib.URIRef('http://example.com/tag#4321'), rdflib.URIRef(ns.bst.main), rdflib.URIRef('http://example.com/entity#1234')))
 
         # default parser
         self.parser = Fetch(self.schema)
@@ -140,7 +134,7 @@ class TestParseFetch(unittest.TestCase):
         # __call__ requires a parseable root
         self.assertRaises(errors.BackendError, self.parser, self.ent, ast.filter.FilterExpression())
         # __call__ returns an executable query
-        q = self.parser(self.ent, ast.fetch.Fetch(bse.tag, ast.fetch.Value(bst.label, 'label')))
+        q = self.parser(self.ent, ast.fetch.Fetch(ns.bse.tag, ast.fetch.Value(ns.bst.label, 'label')))
         self.assertSetEqual(set(q(self.graph)), {
             (rdflib.URIRef('http://example.com/entity#1234'), rdflib.Literal('tag_label_1234', datatype=rdflib.XSD.string)),
             (rdflib.URIRef('http://example.com/entity#4321'), rdflib.Literal('tag_label_4321', datatype=rdflib.XSD.string)),
@@ -154,8 +148,8 @@ class TestParseFetch(unittest.TestCase):
     def test_all(self):
         # multiple values query
         q = self.parser(self.ent, ast.fetch.All(
-            ast.fetch.Value(bse.filename, name='filename'),
-            ast.fetch.Value(bse.rank, name='rank')),
+            ast.fetch.Value(ns.bse.filename, name='filename'),
+            ast.fetch.Value(ns.bse.rank, name='rank')),
             )
         self.assertSetEqual(set(q.names), {'filename', 'rank'})
         if q.names == ('filename', 'rank'):
@@ -170,8 +164,8 @@ class TestParseFetch(unittest.TestCase):
                 })
         # mixed values and node query
         q = self.parser(self.ent, ast.fetch.All(
-            ast.fetch.Value(bse.filename, name='filename'),
-            ast.fetch.Node(bse.tag, name='tag'),
+            ast.fetch.Value(ns.bse.filename, name='filename'),
+            ast.fetch.Node(ns.bse.tag, name='tag'),
             ))
         self.assertSetEqual(set(q.names), {'filename', 'tag'})
         if q.names == ('filename', 'tag'):
@@ -185,9 +179,9 @@ class TestParseFetch(unittest.TestCase):
                 (rdflib.URIRef('http://example.com/entity#4321'), rdflib.URIRef('http://example.com/tag#4321'), rdflib.Literal('filename_4321', datatype=rdflib.XSD.string)),
                 })
         # multiple values and second hop
-        q = self.parser(self.ent, ast.fetch.Fetch(bse.tag, ast.fetch.All(
+        q = self.parser(self.ent, ast.fetch.Fetch(ns.bse.tag, ast.fetch.All(
             ast.fetch.This(name='tag'),
-            ast.fetch.Value(bst.label, name='label'),
+            ast.fetch.Value(ns.bst.label, name='label'),
             )))
         self.assertSetEqual(set(q.names), {'tag', 'label'})
         if q.names == ('tag', 'label'):
@@ -205,13 +199,13 @@ class TestParseFetch(unittest.TestCase):
 
     def test_fetch(self):
         # two-hop query
-        q = self.parser(self.ent, ast.fetch.Fetch(bse.tag, ast.fetch.Value(bst.label, 'tag_label')))
+        q = self.parser(self.ent, ast.fetch.Fetch(ns.bse.tag, ast.fetch.Value(ns.bst.label, 'tag_label')))
         self.assertSetEqual(set(q(self.graph)), {
             (rdflib.URIRef('http://example.com/entity#1234'), rdflib.Literal('tag_label_1234', datatype=rdflib.XSD.string)),
             (rdflib.URIRef('http://example.com/entity#4321'), rdflib.Literal('tag_label_4321', datatype=rdflib.XSD.string)),
             })
         # three-hop-query
-        q = self.parser(self.ent, ast.fetch.Fetch(bse.tag, ast.fetch.Fetch(bst.main, ast.fetch.Value(bse.rank, 'entity_rank'))))
+        q = self.parser(self.ent, ast.fetch.Fetch(ns.bse.tag, ast.fetch.Fetch(ns.bst.main, ast.fetch.Value(ns.bse.rank, 'entity_rank'))))
         self.assertSetEqual(set(q(self.graph)), {
             (rdflib.URIRef('http://example.com/entity#1234'), None),
             (rdflib.URIRef('http://example.com/entity#4321'), rdflib.Literal('1234', datatype=rdflib.XSD.integer)),
@@ -220,9 +214,9 @@ class TestParseFetch(unittest.TestCase):
 
     def test_node(self):
         # cannot use the internal hop name
-        self.assertRaises(errors.BackendError, self.parser, self.ent, ast.fetch.Node(bse.tag, self.parser.ngen.prefix[1:] + '123'))
+        self.assertRaises(errors.BackendError, self.parser, self.ent, ast.fetch.Node(ns.bse.tag, self.parser.ngen.prefix[1:] + '123'))
         # a simple Node statement
-        q = self.parser(self.ent, ast.fetch.Node(bse.tag, 'tag'))
+        q = self.parser(self.ent, ast.fetch.Node(ns.bse.tag, 'tag'))
         self.assertSetEqual(set(q.names), {'tag'})
         self.assertSetEqual(set(q(self.graph)), {
             (rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef('http://example.com/tag#1234')),
@@ -232,9 +226,9 @@ class TestParseFetch(unittest.TestCase):
 
     def test_value(self):
         # cannot use the internal hop name
-        self.assertRaises(errors.BackendError, self.parser, self.schema.node(ns.bsfs.Entity), ast.fetch.Value(bse.filename, self.parser.ngen.prefix[1:] + '123'))
+        self.assertRaises(errors.BackendError, self.parser, self.schema.node(ns.bsfs.Entity), ast.fetch.Value(ns.bse.filename, self.parser.ngen.prefix[1:] + '123'))
         # a simple Value statement
-        q = self.parser(self.ent, ast.fetch.Value(bse.filename, 'filename'))
+        q = self.parser(self.ent, ast.fetch.Value(ns.bse.filename, 'filename'))
         self.assertSetEqual(set(q.names), {'filename'})
         self.assertSetEqual(set(q(self.graph)), {
             (rdflib.URIRef('http://example.com/entity#1234'), rdflib.Literal('filename_1234', datatype=rdflib.XSD.string)),
diff --git a/test/triple_store/sparql/test_parse_filter.py b/test/triple_store/sparql/test_parse_filter.py
index 6fa0cd3..a45f2ef 100644
--- a/test/triple_store/sparql/test_parse_filter.py
+++ b/test/triple_store/sparql/test_parse_filter.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import rdflib
 import unittest
@@ -20,6 +15,8 @@ from bsfs.triple_store.sparql.parse_filter import Filter
 
 ## code ##
 
+ns.bse = ns.bsfs.Entity()
+
 class TestParseFilter(unittest.TestCase):
     def setUp(self):
         # schema
@@ -27,25 +24,28 @@ class TestParseFilter(unittest.TestCase):
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
 
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsd: <https://schema.bsfs.io/core/distance#>
+            prefix bsa: <https://schema.bsfs.io/core/Literal/Array/>
 
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array .
-            bsfs:Number rdfs:subClassOf bsfs:Literal .
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            bsa:Feature rdfs:subClassOf bsl:Array .
+            bsl:Number rdfs:subClassOf bsfs:Literal .
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Image rdfs:subClassOf bsfs:Entity .
             bsfs:Tag rdfs:subClassOf bsfs:Node .
 
             xsd:string rdfs:subClassOf bsfs:Literal .
-            xsd:integer rdfs:subClassOf bsfs:Number .
+            xsd:integer rdfs:subClassOf bsl:Number .
             bsfs:URI rdfs:subClassOf bsfs:Literal .
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
+            bsfs:Colors rdfs:subClassOf bsa:Feature ;
                 bsfs:dimension "4"^^xsd:integer ;
                 bsfs:dtype xsd:integer ;
-                bsfs:distance bsfs:euclidean .
+                bsfs:distance bsd:euclidean .
 
             bse:colors rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Entity ;
@@ -86,18 +86,18 @@ class TestParseFilter(unittest.TestCase):
         # graph to test queries
         self.graph = rdflib.Graph()
         # schema hierarchies
-        self.graph.add((rdflib.URIRef('http://bsfs.ai/schema/Entity'), rdflib.RDFS.subClassOf, rdflib.URIRef('http://bsfs.ai/schema/Node')))
-        self.graph.add((rdflib.URIRef('http://bsfs.ai/schema/Image'), rdflib.RDFS.subClassOf, rdflib.URIRef('http://bsfs.ai/schema/Entity')))
-        self.graph.add((rdflib.URIRef('http://bsfs.ai/schema/Tag'), rdflib.RDFS.subClassOf, rdflib.URIRef('http://bsfs.ai/schema/Node')))
+        self.graph.add((rdflib.URIRef('https://schema.bsfs.io/core/Entity'), rdflib.RDFS.subClassOf, rdflib.URIRef('https://schema.bsfs.io/core/Node')))
+        self.graph.add((rdflib.URIRef('https://schema.bsfs.io/core/Image'), rdflib.RDFS.subClassOf, rdflib.URIRef('https://schema.bsfs.io/core/Entity')))
+        self.graph.add((rdflib.URIRef('https://schema.bsfs.io/core/Tag'), rdflib.RDFS.subClassOf, rdflib.URIRef('https://schema.bsfs.io/core/Node')))
         # entities
-        self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')))
-        self.graph.add((rdflib.URIRef('http://example.com/entity#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Entity')))
+        self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')))
+        self.graph.add((rdflib.URIRef('http://example.com/entity#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Entity')))
         # tags
-        self.graph.add((rdflib.URIRef('http://example.com/tag#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Tag')))
-        self.graph.add((rdflib.URIRef('http://example.com/tag#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Tag')))
+        self.graph.add((rdflib.URIRef('http://example.com/tag#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Tag')))
+        self.graph.add((rdflib.URIRef('http://example.com/tag#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Tag')))
         # images
-        self.graph.add((rdflib.URIRef('http://example.com/image#1234'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Image')))
-        self.graph.add((rdflib.URIRef('http://example.com/image#4321'), rdflib.RDF.type, rdflib.URIRef('http://bsfs.ai/schema/Image')))
+        self.graph.add((rdflib.URIRef('http://example.com/image#1234'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Image')))
+        self.graph.add((rdflib.URIRef('http://example.com/image#4321'), rdflib.RDF.type, rdflib.URIRef('https://schema.bsfs.io/core/Image')))
         # node comments
         self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef(ns.bse.comment), rdflib.Literal('Me, Myself, and I', datatype=rdflib.XSD.string)))
         self.graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef(ns.bse.comment), rdflib.Literal('hello world', datatype=rdflib.XSD.string)))
@@ -162,6 +162,8 @@ class TestParseFilter(unittest.TestCase):
     def test_is(self):
         # _is requires a node
         self.assertRaises(errors.BackendError, self.parser._is, self.schema.literal(ns.bsfs.Literal), ast.filter.Is('http://example.com/entity#1234'), '?ent')
+        # _is requires a serializable guid
+        self.assertRaises(ValueError, self.parser._is, self.schema.node(ns.bsfs.Entity), ast.filter.Is('http://example.com/entity#foo and bar'), '?ent')
         # a single Is statement
         q = self.parser(self.schema.node(ns.bsfs.Entity), ast.filter.Is('http://example.com/entity#1234'))
         self.assertSetEqual({str(guid) for guid, in q(self.graph)},
diff --git a/test/triple_store/sparql/test_sparql.py b/test/triple_store/sparql/test_sparql.py
index 30876f2..a7e7d37 100644
--- a/test/triple_store/sparql/test_sparql.py
+++ b/test/triple_store/sparql/test_sparql.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import rdflib
 import unittest
@@ -20,22 +15,25 @@ from bsfs.triple_store.sparql.sparql import SparqlStore
 
 ## code ##
 
+ns.bse = ns.bsfs.Entity()
+
 class TestSparqlStore(unittest.TestCase):
     def setUp(self):
         self.schema = bsc.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
 
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Tag rdfs:subClassOf bsfs:Node .
             bsfs:User rdfs:subClassOf bsfs:Node .
             xsd:string rdfs:subClassOf bsfs:Literal .
-            bsfs:Number rdfs:subClassOf bsfs:Literal .
-            bsfs:BinaryBlob rdfs:subClassOf bsfs:Literal .
-            xsd:integer rdfs:subClassOf bsfs:Number .
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            bsl:BinaryBlob rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsl:Number .
 
             # non-unique literal
             bse:comment rdfs:subClassOf bsfs:Predicate ;
@@ -64,7 +62,7 @@ class TestSparqlStore(unittest.TestCase):
             # binary range
             bse:asset rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Entity ;
-                rdfs:range bsfs:BinaryBlob .
+                rdfs:range bsl:BinaryBlob .
 
             ''')
         self.schema_triples = {
@@ -73,12 +71,12 @@ class TestSparqlStore(unittest.TestCase):
             (rdflib.URIRef(ns.bsfs.Tag), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Node)),
             (rdflib.URIRef(ns.bsfs.User), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Node)),
             (rdflib.URIRef(ns.xsd.string), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.bsfs.Array), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.bsfs.BinaryBlob), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.bsfs.Feature), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Array)),
-            (rdflib.URIRef(ns.bsfs.Number), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.bsfs.Time), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.xsd.integer), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Number)),
+            (rdflib.URIRef(ns.bsl.Array), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
+            (rdflib.URIRef(ns.bsl.BinaryBlob), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
+            (rdflib.URIRef(ns.bsl.Array.Feature), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsl.Array)),
+            (rdflib.URIRef(ns.bsl.Number), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
+            (rdflib.URIRef(ns.bsl.Time), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
+            (rdflib.URIRef(ns.xsd.integer), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsl.Number)),
             (rdflib.URIRef(ns.bse.comment), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             (rdflib.URIRef(ns.bse.filesize), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             (rdflib.URIRef(ns.bse.tag), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
@@ -106,7 +104,7 @@ class TestSparqlStore(unittest.TestCase):
         store.schema = bsc.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bsfs: <https://schema.bsfs.io/core/>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Document rdfs:subClassOf bsfs:Entity .
@@ -211,10 +209,10 @@ class TestSparqlStore(unittest.TestCase):
         curr = curr + bsc.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
-            prefix bst: <http://bsfs.ai/schema/Tag#>
-            prefix bsc: <http://bsfs.ai/schema/Collection#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bst: <https://schema.bsfs.io/core/Tag#>
+            prefix bsc: <https://schema.bsfs.io/core/Collection#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Tag rdfs:subClassOf bsfs:Node .
@@ -260,16 +258,16 @@ class TestSparqlStore(unittest.TestCase):
             (rdflib.URIRef(ns.xsd.boolean), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
             (rdflib.URIRef(ns.bse.shared), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             (rdflib.URIRef(ns.bse.partOf), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
-            (rdflib.URIRef('http://bsfs.ai/schema/Tag#usedIn'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
-            (rdflib.URIRef('http://bsfs.ai/schema/Collection#tag'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
-            (rdflib.URIRef('http://bsfs.ai/schema/Tag#principal'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
+            (rdflib.URIRef('https://schema.bsfs.io/core/Tag#usedIn'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
+            (rdflib.URIRef('https://schema.bsfs.io/core/Collection#tag'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
+            (rdflib.URIRef('https://schema.bsfs.io/core/Tag#principal'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             })
         # add some instances of the new classes
         p_partOf = curr.predicate(ns.bse.partOf)
         p_shared = curr.predicate(ns.bse.shared)
-        p_usedIn = curr.predicate('http://bsfs.ai/schema/Tag#usedIn')
-        p_ctag = curr.predicate('http://bsfs.ai/schema/Collection#tag')
-        p_principal = curr.predicate('http://bsfs.ai/schema/Tag#principal')
+        p_usedIn = curr.predicate('https://schema.bsfs.io/core/Tag#usedIn')
+        p_ctag = curr.predicate('https://schema.bsfs.io/core/Collection#tag')
+        p_principal = curr.predicate('https://schema.bsfs.io/core/Tag#principal')
         store.create(curr.node(ns.bsfs.Collection), {URI('http://example.com/me/collection#1234'), URI('http://example.com/me/collection#4321')})
         # add some more triples
         store.set(curr.node(ns.bsfs.Entity), ent_ids, p_shared, {True})
@@ -288,9 +286,9 @@ class TestSparqlStore(unittest.TestCase):
             (rdflib.URIRef(ns.xsd.boolean), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
             (rdflib.URIRef(ns.bse.shared), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             (rdflib.URIRef(ns.bse.partOf), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
-            (rdflib.URIRef('http://bsfs.ai/schema/Tag#usedIn'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
-            (rdflib.URIRef('http://bsfs.ai/schema/Collection#tag'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
-            (rdflib.URIRef('http://bsfs.ai/schema/Tag#principal'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
+            (rdflib.URIRef('https://schema.bsfs.io/core/Tag#usedIn'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
+            (rdflib.URIRef('https://schema.bsfs.io/core/Collection#tag'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
+            (rdflib.URIRef('https://schema.bsfs.io/core/Tag#principal'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             # collections
             (rdflib.URIRef('http://example.com/me/collection#1234'), rdflib.RDF.type, rdflib.URIRef(ns.bsfs.Collection)),
             (rdflib.URIRef('http://example.com/me/collection#4321'), rdflib.RDF.type, rdflib.URIRef(ns.bsfs.Collection)),
@@ -314,17 +312,18 @@ class TestSparqlStore(unittest.TestCase):
         curr = bsc.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
-            prefix bst: <http://bsfs.ai/schema/Tag#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bst: <https://schema.bsfs.io/core/Tag#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Tag rdfs:subClassOf bsfs:Node .
             bsfs:User rdfs:subClassOf bsfs:Node .
 
             xsd:boolean rdfs:subClassOf bsfs:Literal .
-            bsfs:Number rdfs:subClassOf bsfs:Literal .
-            xsd:integer rdfs:subClassOf bsfs:Number .
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsl:Number .
 
             bse:filesize rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Entity ;
@@ -365,16 +364,16 @@ class TestSparqlStore(unittest.TestCase):
             (rdflib.URIRef(ns.bsfs.Tag), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Node)),
             (rdflib.URIRef(ns.bsfs.User), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Node)),
             (rdflib.URIRef(ns.xsd.boolean), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.bsfs.Array), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.bsfs.BinaryBlob), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.bsfs.Feature), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Array)),
-            (rdflib.URIRef(ns.bsfs.Number), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.bsfs.Time), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
-            (rdflib.URIRef(ns.xsd.integer), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Number)),
+            (rdflib.URIRef(ns.bsl.Array), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
+            (rdflib.URIRef(ns.bsl.BinaryBlob), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
+            (rdflib.URIRef(ns.bsl.Array.Feature), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsl.Array)),
+            (rdflib.URIRef(ns.bsl.Number), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
+            (rdflib.URIRef(ns.bsl.Time), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Literal)),
+            (rdflib.URIRef(ns.xsd.integer), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsl.Number)),
             (rdflib.URIRef(ns.bse.shared), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             (rdflib.URIRef(ns.bse.tag), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             (rdflib.URIRef(ns.bse.filesize), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
-            (rdflib.URIRef('http://bsfs.ai/schema/Tag#principal'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
+            (rdflib.URIRef('https://schema.bsfs.io/core/Tag#principal'), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Predicate)),
             # node instances
             (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.RDF.type, rdflib.URIRef(ns.bsfs.Entity)),
             (rdflib.URIRef('http://example.com/me/entity#4321'), rdflib.RDF.type, rdflib.URIRef(ns.bsfs.Entity)),
@@ -405,13 +404,15 @@ class TestSparqlStore(unittest.TestCase):
         invalid = bsc.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
+            prefix bsl: <https://schema.bsfs.io/core/Literal/>
+            prefix bsa: <https://schema.bsfs.io/core/Literal/Array/>
 
-            bsfs:Array rdfs:subClassOf bsfs:Literal .
-            bsfs:Feature rdfs:subClassOf bsfs:Array .
+            bsl:Array rdfs:subClassOf bsfs:Literal .
+            bsa:Feature rdfs:subClassOf bsl:Array .
 
-            bsfs:Colors rdfs:subClassOf bsfs:Feature ;
+            bsfs:Colors rdfs:subClassOf bsa:Feature ;
                 bsfs:dimension "4"^^xsd:integer ;
                 bsfs:distance bsfs:foobar .
 
@@ -422,8 +423,8 @@ class TestSparqlStore(unittest.TestCase):
         invalid = bsc.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:Tag rdfs:subClassOf bsfs:Entity . # inconsistent with previous tag definition
@@ -438,8 +439,8 @@ class TestSparqlStore(unittest.TestCase):
         invalid = bsc.from_string('''
             prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
             prefix xsd: <http://www.w3.org/2001/XMLSchema#>
-            prefix bsfs: <http://bsfs.ai/schema/>
-            prefix bse: <http://bsfs.ai/schema/Entity#>
+            prefix bsfs: <https://schema.bsfs.io/core/>
+            prefix bse: <https://schema.bsfs.io/core/Entity#>
 
             bsfs:Entity rdfs:subClassOf bsfs:Node .
             bsfs:User rdfs:subClassOf bsfs:Node .
@@ -683,6 +684,9 @@ class TestSparqlStore(unittest.TestCase):
         self.assertRaises(errors.ConsistencyError, store.create, self.schema.node(ns.bsfs.Entity).child(ns.bsfs.invalid), {
             URI('http://example.com/me/entity#1234'), URI('http://example.com/me/entity#4321')})
 
+        # guid must be valid
+        self.assertRaises(ValueError, store.create, self.schema.node(ns.bsfs.Entity), {'http://example.com/me/foo and bar'})
+
         # can create some nodes
         ent_type = store.schema.node(ns.bsfs.Entity)
         store.create(ent_type, {URI('http://example.com/me/entity#1234'), URI('http://example.com/me/entity#4321')})
@@ -771,6 +775,9 @@ class TestSparqlStore(unittest.TestCase):
         # invalid predicate is not permitted
         self.assertRaises(errors.ConsistencyError, store.set, ent_type, ent_ids, p_invalid, {'http://example.com/me/tag#1234'})
 
+        # invalid guid is not permitted
+        self.assertRaises(ValueError, store.set, ent_type, {'http://example.com/me/foo and bar'}, p_filesize, {1234})
+
         # predicate must match node_type
         self.assertRaises(errors.ConsistencyError, store.set, tag_type, tag_ids, p_filesize, {1234})
 
@@ -944,9 +951,9 @@ class TestSparqlStore(unittest.TestCase):
         p_asset = store.schema.predicate(ns.bse.asset)
         store.set(ent_type, ent_ids, p_asset, {bytes(range(128)), bytes(range(128, 256))})
         blob1 = rdflib.Literal('AAECAwQFBgcICQoLDA0ODxAREhMUFRYXGBkaGxwdHh8gISIjJCUmJygpKissLS4vMDEyMzQ1Njc4OTo7PD0+P0BBQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWltcXV5fYGFiY2RlZmdoaWprbG1ub3BxcnN0dXZ3eHl6e3x9fn8=',
-            datatype=rdflib.URIRef(ns.bsfs.BinaryBlob))
+            datatype=rdflib.URIRef(ns.bsl.BinaryBlob))
         blob2 = rdflib.Literal('gIGCg4SFhoeIiYqLjI2Oj5CRkpOUlZaXmJmam5ydnp+goaKjpKWmp6ipqqusra6vsLGys7S1tre4ubq7vL2+v8DBwsPExcbHyMnKy8zNzs/Q0dLT1NXW19jZ2tvc3d7f4OHi4+Tl5ufo6err7O3u7/Dx8vP09fb3+Pn6+/z9/v8=',
-            datatype=rdflib.URIRef(ns.bsfs.BinaryBlob))
+            datatype=rdflib.URIRef(ns.bsl.BinaryBlob))
         self.assertTrue(set(store._graph).issuperset({
             (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(p_asset.uri), blob1),
             (rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(p_asset.uri), blob2),
diff --git a/test/triple_store/sparql/test_utils.py b/test/triple_store/sparql/test_utils.py
index 073b8f8..44a1299 100644
--- a/test/triple_store/sparql/test_utils.py
+++ b/test/triple_store/sparql/test_utils.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # standard imports
 import operator
 import re
@@ -21,6 +16,8 @@ from bsfs.triple_store.sparql.utils import GenHopName, Query
 
 ## code ##
 
+ns.bse = ns.bsfs.Entity()
+
 class TestGenHopName(unittest.TestCase):
     def test_next(self):
         # baseline
@@ -45,7 +42,7 @@ class TestGenHopName(unittest.TestCase):
 
 class TestQuery(unittest.TestCase):
     def setUp(self):
-        self.root_type = 'http://bsfs.ai/schema/Entity'
+        self.root_type = 'https://schema.bsfs.io/core/Entity'
         self.root_head = '?root'
         self.select = (('?head', 'name'), )
         self.where = f'?root <{ns.bse.tag}> ?head'
@@ -61,8 +58,8 @@ class TestQuery(unittest.TestCase):
         self.assertEqual(q, Query(self.root_type, self.root_head, self.select, self.where))
         self.assertEqual(hash(q), hash(Query(self.root_type, self.root_head, self.select, self.where)))
         # comparison respects root_type
-        self.assertNotEqual(q, Query('http://bsfs.ai/schema/Tag', self.root_head, self.select, self.where))
-        self.assertNotEqual(hash(q), hash(Query('http://bsfs.ai/schema/Tag', self.root_head, self.select, self.where)))
+        self.assertNotEqual(q, Query('https://schema.bsfs.io/core/Tag', self.root_head, self.select, self.where))
+        self.assertNotEqual(hash(q), hash(Query('https://schema.bsfs.io/core/Tag', self.root_head, self.select, self.where)))
         # comparison respects root_head
         self.assertNotEqual(q, Query(self.root_type, '?foo', self.select, self.where))
         self.assertNotEqual(hash(q), hash(Query(self.root_type, '?foo', self.select, self.where)))
@@ -74,7 +71,7 @@ class TestQuery(unittest.TestCase):
         self.assertNotEqual(hash(q), hash(Query(self.root_type, self.root_head, self.select, '?root bse:filename ?head')))
         # string conversion
         self.assertEqual(str(q), q.query)
-        self.assertEqual(repr(q), "Query(http://bsfs.ai/schema/Entity, ?root, (('?head', 'name'),), ?root <http://bsfs.ai/schema/Entity#tag> ?head)")
+        self.assertEqual(repr(q), "Query(https://schema.bsfs.io/core/Entity, ?root, (('?head', 'name'),), ?root <https://schema.bsfs.io/core/Entity#tag> ?head)")
 
     def test_add(self):
         q = Query(self.root_type, self.root_head, self.select, self.where)
@@ -82,7 +79,7 @@ class TestQuery(unittest.TestCase):
         self.assertRaises(TypeError, operator.add, q, 1234)
         self.assertRaises(TypeError, operator.add, q, 'foobar')
         # root type and head must match
-        self.assertRaises(ValueError, operator.add, q, Query('http://bsfs.ai/schema/Tag', self.root_head))
+        self.assertRaises(ValueError, operator.add, q, Query('https://schema.bsfs.io/core/Node/Tag', self.root_head))
         self.assertRaises(ValueError, operator.add, q, Query(self.root_type, '?foobar'))
         # select and were are combined
         combo = q + Query(self.root_type, self.root_head, (('?foo', 'bar'), ), f'?root <{ns.bse.filename}> ?foo')
@@ -118,23 +115,23 @@ class TestQuery(unittest.TestCase):
             return value
         # query composes a valid query
         q = Query(self.root_type, self.root_head, self.select, self.where)
-        self.assertEqual(normalize(q.query), normalize(f'select ?root (?head as ?name) where {{ ?root <{ns.rdf.type}>/<{ns.rdfs.subClassOf}>* <http://bsfs.ai/schema/Entity> . ?root <{ns.bse.tag}> ?head }}'))
+        self.assertEqual(normalize(q.query), normalize(f'select distinct ?root (?head as ?name) where {{ ?root <{ns.rdf.type}>/<{ns.rdfs.subClassOf}>* <https://schema.bsfs.io/core/Entity> . ?root <{ns.bse.tag}> ?head }} order by str(?root)'))
         # select and where are optional
         q = Query(self.root_type, self.root_head)
-        self.assertEqual(normalize(q.query), normalize(f'select ?root where {{ ?root <{ns.rdf.type}>/<{ns.rdfs.subClassOf}>* <http://bsfs.ai/schema/Entity> . }}'))
+        self.assertEqual(normalize(q.query), normalize(f'select distinct ?root where {{ ?root <{ns.rdf.type}>/<{ns.rdfs.subClassOf}>* <https://schema.bsfs.io/core/Entity> . }} order by str(?root)'))
         # select and where need not to correspond
         q = Query(self.root_type, self.root_head, (('?head', 'name'), ))
-        self.assertEqual(normalize(q.query), normalize(f'select ?root (?head as ?name) where {{ ?root <{ns.rdf.type}>/<{ns.rdfs.subClassOf}>* <http://bsfs.ai/schema/Entity> . }}'))
+        self.assertEqual(normalize(q.query), normalize(f'select distinct ?root (?head as ?name) where {{ ?root <{ns.rdf.type}>/<{ns.rdfs.subClassOf}>* <https://schema.bsfs.io/core/Entity> . }} order by str(?root)'))
         # query is used for string representation
         self.assertEqual(str(q), q.query)
 
     def test_call(self):
         graph = rdflib.Graph()
         # schema
-        graph.add((rdflib.URIRef('http://bsfs.ai/schema/Document'), rdflib.URIRef(ns.rdfs.subClassOf), rdflib.URIRef('http://bsfs.ai/schema/Entity')))
+        graph.add((rdflib.URIRef('https://schema.bsfs.io/core/Document'), rdflib.URIRef(ns.rdfs.subClassOf), rdflib.URIRef('https://schema.bsfs.io/core/Entity')))
         # nodes
-        graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef(ns.rdf.type), rdflib.URIRef('http://bsfs.ai/schema/Entity')))
-        graph.add((rdflib.URIRef('http://example.com/doc#1234'), rdflib.URIRef(ns.rdf.type), rdflib.URIRef('http://bsfs.ai/schema/Document')))
+        graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef(ns.rdf.type), rdflib.URIRef('https://schema.bsfs.io/core/Entity')))
+        graph.add((rdflib.URIRef('http://example.com/doc#1234'), rdflib.URIRef(ns.rdf.type), rdflib.URIRef('https://schema.bsfs.io/core/Document')))
         # links
         graph.add((rdflib.URIRef('http://example.com/entity#1234'), rdflib.URIRef(ns.bse.tag), rdflib.Literal('tag#1234', datatype=rdflib.XSD.string)))
         graph.add((rdflib.URIRef('http://example.com/doc#1234'), rdflib.URIRef(ns.bse.tag), rdflib.Literal('tag#1234', datatype=rdflib.XSD.string)))
diff --git a/test/triple_store/test_base.py b/test/triple_store/test_base.py
index 56a2539..4c4a9b6 100644
--- a/test/triple_store/test_base.py
+++ b/test/triple_store/test_base.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import unittest
 
diff --git a/test/utils/test_commons.py b/test/utils/test_commons.py
index 3ad6dea..29e3046 100644
--- a/test/utils/test_commons.py
+++ b/test/utils/test_commons.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the tagit test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import unittest
 
diff --git a/test/utils/test_uri.py b/test/utils/test_uri.py
index 770e65a..1c4c9f9 100644
--- a/test/utils/test_uri.py
+++ b/test/utils/test_uri.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the tagit test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import operator
 import unittest
@@ -40,6 +35,16 @@ class TestURI(unittest.TestCase):
         self.assertTrue(URI.is_parseable('telnet://192.0.2.16:80/'))
         self.assertTrue(URI.is_parseable('urn:oasis:names:specification:docbook:dtd:xml:4.1.2'))
 
+        # some characters are prohibited
+        self.assertFalse(URI.is_parseable('http://example.com/foo<bar'))
+        self.assertFalse(URI.is_parseable('http://example.com/foo>bar'))
+        self.assertFalse(URI.is_parseable('http://example.com/foo bar'))
+        self.assertFalse(URI.is_parseable('http://example.com/foo{bar'))
+        self.assertFalse(URI.is_parseable('http://example.com/foo}bar'))
+        self.assertFalse(URI.is_parseable('http://example.com/foo|bar'))
+        self.assertFalse(URI.is_parseable('http://example.com/foo^bar'))
+        self.assertFalse(URI.is_parseable('http://example.com/foo\\bar'))
+
         # uri cannot end with a scheme delimiter
         self.assertFalse(URI.is_parseable('http://'))
         # port must be a number
@@ -164,10 +169,10 @@ class TestURI(unittest.TestCase):
 
     def test_overloaded(self):
         # composition
-        self.assertIsInstance(URI('http://user@www.example.com:1234/{}/path1?{}#fragment') + 'hello', URI)
-        self.assertIsInstance(URI('http://user@www.example.com:1234/{}/path1?{}#fragment') * 2, URI)
-        self.assertIsInstance(2 * URI('http://user@www.example.com:1234/{}/path1?{}#fragment'), URI) # rmul
-        self.assertIsInstance(URI('http://user@www.example.com:1234/{}/path1?{}#fragment').join(['hello', 'world']) , URI)
+        self.assertIsInstance(URI('http://user@www.example.com:1234/path0/path1?query#fragment') + 'hello', URI)
+        self.assertIsInstance(URI('http://user@www.example.com:1234/path0/path1?query#fragment') * 2, URI)
+        self.assertIsInstance(2 * URI('http://user@www.example.com:1234/path0/path1?query#fragment'), URI) # rmul
+        self.assertIsInstance(URI('http://user@www.example.com:1234/path0/path1?query#fragment').join(['hello', 'world']) , URI)
         # stripping
         self.assertIsInstance(URI('http://user@www.example.com:1234/path0/path1?query#fragment').strip(), URI)
         self.assertIsInstance(URI('http://user@www.example.com:1234/path0/path1?query#fragment').lstrip(), URI)
@@ -176,7 +181,6 @@ class TestURI(unittest.TestCase):
         self.assertIsInstance(URI('http://user@www.example.com:1234/path0/path1?query#fragment').lower(), URI)
         self.assertIsInstance(URI('http://user@www.example.com:1234/path0/path1?query#fragment').upper(), URI)
         # formatting
-        self.assertIsInstance(URI('http://user@www.example.com:1234/{}/path1?{}#fragment').format('hello', 'world'), URI)
         self.assertIsInstance(URI('http://user@www.example.com:1234/%s/path1?%s#fragment') % ('hello', 'world'), URI)
         self.assertIsInstance(URI('http://user@www.example.com:1234/path0/path1?query#fragment').replace('path0', 'pathX'), URI)
 
diff --git a/test/utils/test_uuid.py b/test/utils/test_uuid.py
index 804b063..8f519d9 100644
--- a/test/utils/test_uuid.py
+++ b/test/utils/test_uuid.py
@@ -1,9 +1,4 @@
-"""
 
-Part of the tagit test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import os
 import re