Merge branch 'develop'v0.23.03

7 files changed, 1515 insertions, 157 deletions

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 f39c9be..142bc23 100644
--- a/test/graph/ac/test_null.py
+++ b/test/graph/ac/test_null.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
 
 # bsie imports
-from bsfs import schema as _schema
+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
 
@@ -19,24 +15,28 @@ from bsfs.graph.ac.null import NullAC
 
 ## code ##
 
+ns.bse = ns.bsfs.Entity()
+
 class TestNullAC(unittest.TestCase):
     def setUp(self):
         self.backend = SparqlStore()
-        self.backend.schema = _schema.Schema.from_string('''
+        self.backend.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 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 .
-            xsd:integer rdfs:subClassOf bsfs:Literal .
+            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 .
@@ -62,10 +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))
@@ -93,6 +123,26 @@ class TestNullAC(unittest.TestCase):
         ac = NullAC(self.backend, self.user)
         self.assertSetEqual(self.ent_ids, ac.createable(self.ent_type, self.ent_ids))
 
+    def test_filter_read(self):
+        query = ast.filter.Or(
+            ast.filter.Any(ns.bse.tag, ast.filter.Is('http://example.com/tag#1234')),
+            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))
+        # 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 33cf6aa..167168d 100644
--- a/test/graph/test_graph.py
+++ b/test/graph/test_graph.py
@@ -1,18 +1,17 @@
-"""
 
-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
 from bsfs.triple_store import SparqlStore
 from bsfs.utils import URI, errors
-from bsfs.graph.nodes import Nodes
 
 # objects to test
 from bsfs.graph.graph import Graph
@@ -20,83 +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.Schema.from_string('''
+        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_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.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
@@ -117,14 +128,16 @@ class TestGraph(unittest.TestCase):
                     schema.Node(ns.bsfs.Node, None)))}), append=False)
 
         # can migrate to compatible schema
-        target_1 = schema.Schema.from_string('''
+        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 .
-            xsd:integer rdfs:subClassOf bsfs:Literal .
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsl:Number .
 
             bse:filename rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Entity ;
@@ -141,27 +154,31 @@ class TestGraph(unittest.TestCase):
         # new schema is applied
         self.assertLess(target_1, graph.schema)
         # graph appends its predicates
-        self.assertEqual(graph.schema, target_1 + schema.Schema.from_string('''
+        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#>
-            xsd:integer rdfs:subClassOf bsfs:Literal .
-            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 .
             '''))
 
         # can overwrite the current schema
-        target_2 = schema.Schema.from_string('''
+        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 .
-            xsd:integer rdfs:subClassOf bsfs:Literal .
+            bsl:Number rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsl:Number .
 
             bse:filename rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Entity ;
@@ -180,18 +197,147 @@ class TestGraph(unittest.TestCase):
         # new schema is applied
         self.assertLess(target_2, graph.schema)
         # graph appends its predicates
-        self.assertEqual(graph.schema, target_2 + schema.Schema.from_string('''
+        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#>
-            xsd:integer rdfs:subClassOf bsfs:Literal .
-            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.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 = graph.nodes(ns.bsfs.Entity, {URI('http://example.com/entity#1234'), 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
+        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, graph.get, ns.bsfs.Entity, ast.filter.Any(ns.bse.tag, ast.filter.Equals('hello world')))
+
+        # 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')))
+        self.assertEqual(graph.get(ns.bsfs.Node, ast.filter.Any(ns.bse.comment, ast.filter.StartsWith('foo'))),
+            graph.nodes(ns.bsfs.Node, {URI('http://example.com/entity#1234'), URI('http://example.com/tag#1234')}))
+        self.assertEqual(graph.get(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.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)
+
+
 
 ## main ##
 
diff --git a/test/graph/test_nodes.py b/test/graph/test_nodes.py
index 43e7f6f..afe7522 100644
--- a/test/graph/test_nodes.py
+++ b/test/graph/test_nodes.py
@@ -1,16 +1,17 @@
-"""
 
-Part of the bsfs test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
-# imports
-import rdflib
+# standard imports
+from functools import partial
+import operator
 import unittest
 
+# external imports
+import rdflib
+
 # bsie imports
-from bsfs import schema as _schema
-from bsfs.namespace import ns
+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
 from bsfs.utils import errors, URI
 
@@ -20,27 +21,32 @@ from bsfs.graph.nodes import Nodes
 
 ## code ##
 
+ns.bse = ns.bsfs.Entity()
+ns.bst = ns.bsfs.Tag()
+
 class TestNodes(unittest.TestCase):
     def setUp(self):
         # initialize backend
         self.backend = SparqlStore()
-        self.backend.schema = _schema.Schema.from_string('''
+        self.backend.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 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 .
-            xsd:integer rdfs:subClassOf bsfs:Literal .
+            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 .
@@ -66,14 +72,40 @@ class TestNodes(unittest.TestCase):
                 rdfs:range bsfs:User ;
                 bsfs:unique "true"^^xsd:boolean .
 
+            bst:label rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Tag ;
+                rdfs:range xsd:string ;
+                bsfs:unique "true"^^xsd:boolean .
+
             bst:representative rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Tag ;
                 rdfs:range bsfs:Entity ;
                 bsfs:unique "true"^^xsd:boolean .
 
             ''')
+        self.schema_triples = {
+            # schema hierarchy
+            (rdflib.URIRef(ns.bsfs.Entity), rdflib.RDFS.subClassOf, rdflib.URIRef(ns.bsfs.Node)),
+            (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.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(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)
@@ -81,8 +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(URI('http://bsfs.ai/schema/Tag#representative'))
-        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'),
@@ -92,67 +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))
@@ -160,10 +197,10 @@ class TestNodes(unittest.TestCase):
         time_triples = list(self.backend._graph.objects(rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(self.t_created.uri)))
         t_ent_created = float(time_triples[0]) if len(time_triples) > 0 else 0.0
         # check triples
-        self.assertSetEqual(set(self.backend._graph), {
+        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)),
@@ -171,10 +208,10 @@ class TestNodes(unittest.TestCase):
 
         # existing nodes remain unchanged
         self.assertSetEqual(self.ent_ids, nodes._ensure_nodes(self.ent_type, self.ent_ids))
-        self.assertSetEqual(set(self.backend._graph), {
+        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)),
@@ -186,23 +223,23 @@ class TestNodes(unittest.TestCase):
         time_triples = list(self.backend._graph.objects(rdflib.URIRef('http://example.com/me/tag#1234'), rdflib.URIRef(self.t_created.uri)))
         t_tag_created = float(time_triples[0]) if len(time_triples) > 0 else 0.0
         # check triples
-        self.assertSetEqual(set(self.backend._graph), {
+        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')})
-        self.assertSetEqual(set(self.backend._graph), set())
+        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
 
         # node_type must match predicate's domain
@@ -217,10 +254,10 @@ class TestNodes(unittest.TestCase):
         time_triples = list(self.backend._graph.objects(rdflib.URIRef('http://example.com/me/entity#1234'), rdflib.URIRef(self.t_created.uri)))
         t_ent_created = float(time_triples[0]) if len(time_triples) > 0 else 0.0
         # verify triples
-        self.assertSetEqual(set(self.backend._graph), {
+        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)),
@@ -230,23 +267,23 @@ 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)))
         t_tag_created = float(time_triples[0]) if len(time_triples) > 0 else 0.0
         # verify triples
-        self.assertSetEqual(set(self.backend._graph), {
+        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)),
@@ -262,29 +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), set())
-        nodes = Nodes(self.backend, self.user, self.ent_type, self.ent_ids)
+        self.assertSetEqual(set(self.backend._graph), self.schema_triples | set())
+        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')),
@@ -307,24 +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), set())
-        nodes = Nodes(self.backend, self.user, self.ent_type, self.ent_ids)
+        self.assertSetEqual(set(self.backend._graph), self.schema_triples | set())
+        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)),
@@ -349,9 +390,254 @@ 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.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.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.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.ac, self.ent_type, self.ent_ids)
+
+        # must pass at least one path
+        self.assertRaises(AttributeError, nodes.get)
+        # view must be list or dict
+        self.assertRaises(ValueError, nodes.get, ns.bse.filesize, view='hello')
+        self.assertRaises(ValueError, nodes.get, ns.bse.filesize, view=1234)
+        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.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, 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, 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, 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(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, ns.bst.invalid))
+        # can pass multiple paths
+        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, ns.bst.label): {'tag_label_1234'},
+                },
+            Nodes(self.backend, self.ac, self.ent_type, {'http://example.com/me/entity#4321'}): {
+                ns.bse.filesize: 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.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.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.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.ac, self.ent_type, {'http://example.com/me/entity#1234'}): {'hello world'},
+            })
+
+        # 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.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
+        self.assertEqual(nodes.tag, Walk(nodes, (self.p_tag, )))
+        # can do multiple hops
+        self.assertEqual(nodes.tag.label, Walk(nodes, (self.p_tag, self.p_label)))
+        # invalid step raises an error
+        self.assertRaises(ValueError, getattr, nodes, 'foobar')
+
+    def test_schema(self):
+        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.ac, self.ent_type)
+        nodes = gen({URI('http://example.com/me/entity#1234')})
+        # add/or concatenates guids
+        self.assertEqual(
+            gen({URI('http://example.com/me/entity#1234')}) +
+            gen({URI('http://example.com/me/entity#4321')}),
+            # target
+            gen({
+                URI('http://example.com/me/entity#1234'),
+                URI('http://example.com/me/entity#4321')}))
+        self.assertEqual(
+            gen({URI('http://example.com/me/entity#1234')}) |
+            gen({URI('http://example.com/me/entity#4321')}),
+            # target
+            gen({
+                URI('http://example.com/me/entity#1234'),
+                URI('http://example.com/me/entity#4321')}))
+        # repeated guids are ignored
+        self.assertEqual(
+            gen({URI('http://example.com/me/entity#1234')}) +
+            gen({URI('http://example.com/me/entity#1234')}),
+            # target
+            gen({URI('http://example.com/me/entity#1234')}))
+        self.assertEqual(
+            gen({URI('http://example.com/me/entity#1234')}) |
+            gen({URI('http://example.com/me/entity#1234')}),
+            # target
+            gen({URI('http://example.com/me/entity#1234')}))
+
+        # sub substracts guids
+        self.assertEqual(
+            gen({URI('http://example.com/me/entity#1234'),
+                 URI('http://example.com/me/entity#4321')}) -
+            gen({URI('http://example.com/me/entity#4321')}),
+            # target
+            gen({URI('http://example.com/me/entity#1234')}))
+        # missing guids are ignored
+        self.assertEqual(
+            gen({URI('http://example.com/me/entity#1234')}) -
+            gen({URI('http://example.com/me/entity#4321')}),
+            # target
+            gen({URI('http://example.com/me/entity#1234')}))
+
+        # and intersects guids
+        self.assertEqual(
+            gen({URI('http://example.com/me/entity#1234'),
+                 URI('http://example.com/me/entity#4321')}) &
+            gen({URI('http://example.com/me/entity#4321'),
+                 URI('http://example.com/me/entity#5678')}),
+            # target
+            gen({URI('http://example.com/me/entity#4321')}))
+
+        for op in (operator.add, operator.or_, operator.sub, operator.and_):
+            # type must match
+            self.assertRaises(TypeError, op, nodes, 1234)
+            self.assertRaises(TypeError, op, nodes, 'hello world')
+            # backend must match
+            self.assertRaises(ValueError, op, nodes,
+                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, 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.ac, self.tag_type, {URI('http://example.com/me/entity#1234')}))
+
+    def test_len(self):
+        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.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.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'),
+            URI('http://example.com/me/entity#8765'),
+            })))
+
+    def test_iter(self): # __iter__
+        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'),
+            URI('http://example.com/me/entity#8765'),
+            })), {
+            gen({URI('http://example.com/me/entity#1234')}),
+            gen({URI('http://example.com/me/entity#4321')}),
+            gen({URI('http://example.com/me/entity#5678')}),
+            gen({URI('http://example.com/me/entity#8765')}),
+            })
+
 
 ## main ##
 
diff --git a/test/graph/test_resolve.py b/test/graph/test_resolve.py
new file mode 100644
index 0000000..e09b1cc
--- /dev/null
+++ b/test/graph/test_resolve.py
@@ -0,0 +1,199 @@
+
+# imports
+import unittest
+
+# bsie imports
+from bsfs import schema as bsc
+from bsfs.graph import Graph, nodes
+from bsfs.namespace import ns
+from bsfs.query import ast
+from bsfs.triple_store import SparqlStore
+from bsfs.utils import URI, errors
+
+# objects to test
+from bsfs.graph.resolve import Filter
+
+
+## code ##
+
+ns.bse = ns.bsfs.Entity()
+
+class TestFilter(unittest.TestCase):
+    """
+
+    NOTE: The Filter resolver is relatively simple as it only checks and changes
+    ast.filter.Is instances. Hence, we don't test all methods individually but
+    all of them with respect to ast.filter.Is elements.
+
+    """
+
+    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: <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 .
+            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 bsa:Feature ;
+                bsfs:dimension "5"^^xsd:integer .
+
+            bse:colors rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range bsfs:Colors .
+
+            bse:comment rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range xsd:string ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            bse:filesize rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range xsd:integer ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            bse:tag rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range bsfs:Tag ;
+                bsfs:unique "false"^^xsd:boolean .
+            ''')
+        backend = SparqlStore.Open()
+        backend.schema = schema
+        graph = Graph(backend, URI('http://example.com/me'))
+        ents = graph.nodes(ns.bsfs.Entity,
+            {URI('http://example.com/me/entity#1234'), URI('http://example.com/me/entity#4321')})
+        tags = graph.nodes(ns.bsfs.Tag,
+            {URI('http://example.com/me/tag#1234'), URI('http://example.com/me/tag#4321')})
+        invalid = nodes.Nodes(None, '', schema.node(ns.bsfs.Node).child(ns.bsfs.Invalid),
+            {'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)),
+            ast.filter.Or(
+                ast.filter.Is('http://example.com/me/entity#1234'),
+                ast.filter.Is('http://example.com/me/entity#4321')
+                ))
+        # only resolves nodes instances, not URIs
+        self.assertEqual(resolver(schema.node(ns.bsfs.Entity),
+            ast.filter.Is('http://example.com/me/entity#1234')),
+            ast.filter.Is('http://example.com/me/entity#1234'))
+        self.assertEqual(resolver(schema.node(ns.bsfs.Entity),
+            ast.filter.Is(1234)),
+            ast.filter.Is(1234))
+
+        # within And (also checks _value)
+        self.assertEqual(resolver(schema.node(ns.bsfs.Entity),
+            ast.filter.And(
+                ast.filter.Is(ents),
+                ast.filter.Any(ns.bse.comment, ast.filter.Equals('hello world')),
+            )),
+            ast.filter.And(
+                ast.filter.Or(
+                    ast.filter.Is('http://example.com/me/entity#1234'),
+                    ast.filter.Is('http://example.com/me/entity#4321')),
+                ast.filter.Any(ns.bse.comment, ast.filter.Equals('hello world'))
+            ))
+        # within Or (checks _bounded)
+        self.assertEqual(resolver(schema.node(ns.bsfs.Entity),
+            ast.filter.Or(
+                ast.filter.Is(ents),
+                ast.filter.Any(ns.bse.filesize, ast.filter.LessThan(5)),
+            )),
+            ast.filter.Or(
+                ast.filter.Or(
+                    ast.filter.Is('http://example.com/me/entity#1234'),
+                    ast.filter.Is('http://example.com/me/entity#4321')),
+                ast.filter.Any(ns.bse.filesize, ast.filter.LessThan(5))
+            ))
+
+        # Any-branched Is
+        self.assertEqual(resolver(schema.node(ns.bsfs.Entity),
+            ast.filter.Any(ns.bse.tag, ast.filter.Is(tags))),
+            ast.filter.Any(ns.bse.tag, ast.filter.Or(
+                ast.filter.Is('http://example.com/me/tag#1234'),
+                ast.filter.Is('http://example.com/me/tag#4321')),
+                ))
+        # All-branched Is
+        self.assertEqual(resolver(schema.node(ns.bsfs.Entity),
+            ast.filter.All(ns.bse.tag, ast.filter.Is(tags))),
+            ast.filter.All(ns.bse.tag, ast.filter.Or(
+                ast.filter.Is('http://example.com/me/tag#1234'),
+                ast.filter.Is('http://example.com/me/tag#4321')),
+                ))
+        # Negated predicate
+        self.assertEqual(resolver(schema.node(ns.bsfs.Tag),
+            ast.filter.Any(ast.filter.Predicate(ns.bse.tag, reverse=True), ast.filter.Is(ents))),
+            ast.filter.Any(ast.filter.Predicate(ns.bse.tag, reverse=True), ast.filter.Or(
+                ast.filter.Is('http://example.com/me/entity#1234'),
+                ast.filter.Is('http://example.com/me/entity#4321')),
+                ))
+
+        # negated Is
+        self.assertEqual(resolver(schema.node(ns.bsfs.Entity),
+            ast.filter.Not(ast.filter.Is(ents))),
+            ast.filter.Not(
+                ast.filter.Or(
+                    ast.filter.Is('http://example.com/me/entity#1234'),
+                    ast.filter.Is('http://example.com/me/entity#4321')),
+            ))
+
+        # for sake of completeness: Has
+        self.assertEqual(resolver(schema.node(ns.bsfs.Entity),
+            ast.filter.Has(ns.bse.comment)),
+            ast.filter.Has(ns.bse.comment))
+        # for sake of completeness: Distance
+        self.assertEqual(resolver(schema.node(ns.bsfs.Entity),
+            ast.filter.Any(ns.bse.colors, ast.filter.Distance([1,2,3,4,5], 1))),
+            ast.filter.Any(ns.bse.colors, ast.filter.Distance([1,2,3,4,5], 1)))
+        # route errors
+        self.assertRaises(errors.BackendError, resolver, schema.node(ns.bsfs.Tag),
+            ast.filter.Predicate(ns.bse.comment))
+        self.assertRaises(errors.BackendError, resolver, schema.node(ns.bsfs.Tag),
+            ast.filter.Any(ast.filter.PredicateExpression(), ast.filter.Equals('foo')))
+        self.assertRaises(errors.BackendError, resolver._one_of, ast.filter.OneOf(ast.filter.Predicate(ns.bsfs.Predicate)))
+        # for sake of coverage completeness: valid OneOf
+        self.assertIsNotNone(resolver._one_of(ast.filter.OneOf(ast.filter.Predicate(ns.bse.colors))))
+
+        # check schema consistency
+        self.assertRaises(errors.ConsistencyError, resolver, schema.node(ns.bsfs.Tag),
+            ast.filter.Is(invalid))
+        # check immediate type compatibility
+        self.assertRaises(errors.ConsistencyError, resolver, schema.node(ns.bsfs.Tag),
+            ast.filter.Is(ents))
+        self.assertRaises(errors.ConsistencyError, resolver, schema.node(ns.bsfs.Entity),
+            ast.filter.Is(tags))
+        # check type compatibility through branches
+        self.assertRaises(errors.ConsistencyError, resolver, schema.node(ns.bsfs.Tag),
+            ast.filter.Any(ns.bse.comment, ast.filter.Is(tags)))
+        self.assertRaises(errors.ConsistencyError, resolver, schema.node(ns.bsfs.Tag),
+            ast.filter.Any(ns.bse.invalid, ast.filter.Is(tags)))
+        self.assertRaises(errors.ConsistencyError, resolver, schema.node(ns.bsfs.Tag),
+            ast.filter.Any(ast.filter.OneOf(ns.bse.comment, ns.bse.tag), ast.filter.Is(tags)))
+        self.assertRaises(errors.ConsistencyError, resolver, schema.node(ns.bsfs.Tag),
+            ast.filter.Any(ast.filter.OneOf(ns.bse.comment, ns.bse.filesize), ast.filter.Is(tags)))
+        self.assertRaises(errors.ConsistencyError, resolver, schema.node(ns.bsfs.Tag),
+            ast.filter.Any(ast.filter.Predicate(ns.bse.tag, reverse=True), ast.filter.Is(tags)))
+
+
+
+## main ##
+
+if __name__ == '__main__':
+    unittest.main()
+
+## EOF ##
diff --git a/test/graph/test_result.py b/test/graph/test_result.py
new file mode 100644
index 0000000..8960ef6
--- /dev/null
+++ b/test/graph/test_result.py
@@ -0,0 +1,429 @@
+
+# imports
+import unittest
+
+# bsie imports
+from bsfs import schema as bsc
+from bsfs.namespace import ns
+from bsfs.utils import URI
+
+# objects to test
+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)]
+        self.triples_11U = [('ent#1234', ns.bse.tag, 'tag#1234'),
+                            ('ent#1234', ns.bse.tag, 'tag#5678')]
+        self.triples_1M1 = [('ent#1234', ns.bse.iso, 123),
+                            ('ent#1234', ns.bse.t_created, '2010-01-02')]
+        self.triples_1MU = [('ent#1234', ns.bse.iso, 123),
+                            ('ent#1234', ns.bse.tag, 'tag#1234'),
+                            ('ent#1234', ns.bse.tag, 'tag#5678')]
+        self.triples_N11 = [('ent#1234', ns.bse.iso, 123),
+                            ('ent#4321', ns.bse.iso, 321)]
+        self.triples_N1U = [('ent#1234', ns.bse.tag, 'tag#1234'),
+                            ('ent#1234', ns.bse.tag, 'tag#5678'),
+                            ('ent#4321', ns.bse.tag, 'tag#4321')]
+        self.triples_NM1 = [('ent#1234', ns.bse.iso, 123),
+                            ('ent#1234', ns.bse.t_created, '2010-01-02'),
+                            ('ent#4321', ns.bse.iso, 321),
+                            ('ent#4321', ns.bse.t_created, '2022-02-22')]
+        self.triples_NMU = [('ent#1234', ns.bse.iso, 123),
+                            ('ent#1234', ns.bse.tag, 'tag#1234'),
+                            ('ent#1234', ns.bse.tag, 'tag#5678'),
+                            ('ent#4321', ns.bse.iso, 321),
+                            ('ent#4321', ns.bse.t_created, '2022-02-22')]
+
+    def test_copy(self):
+        # iterator yields tuples
+        self.assertIsInstance(list(to_list_view([('subject', 'predicate', 'object')], node=True, path=True, value=True))[0], tuple)
+        # components are not changed
+        class Foo(): pass
+        foo = Foo()
+        self.assertListEqual(list(to_list_view([('subject', 'predicate', 'object')], node=True, path=True, value=True)),
+            [('subject', 'predicate', 'object')])
+        self.assertListEqual(list(to_list_view([(foo, 'predicate', 'object')], node=True, path=True, value=True)),
+            [(foo, 'predicate', 'object')])
+        self.assertListEqual(list(to_list_view([('subject', foo, 'object')], node=True, path=True, value=True)),
+            [('subject', foo, 'object')])
+        self.assertListEqual(list(to_list_view([('subject', 'predicate', foo)], node=True, path=True, value=True)),
+            [('subject', 'predicate', foo)])
+
+    def test_agg_none(self):
+        self.assertListEqual(list(to_list_view(self.triples_111, node=True, path=True, value=True)), self.triples_111)
+        self.assertListEqual(list(to_list_view(self.triples_11U, node=True, path=True, value=True)), self.triples_11U)
+        self.assertListEqual(list(to_list_view(self.triples_1M1, node=True, path=True, value=True)), self.triples_1M1)
+        self.assertListEqual(list(to_list_view(self.triples_1MU, node=True, path=True, value=True)), self.triples_1MU)
+        self.assertListEqual(list(to_list_view(self.triples_N11, node=True, path=True, value=True)), self.triples_N11)
+        self.assertListEqual(list(to_list_view(self.triples_N1U, node=True, path=True, value=True)), self.triples_N1U)
+        self.assertListEqual(list(to_list_view(self.triples_NM1, node=True, path=True, value=True)), self.triples_NM1)
+        self.assertListEqual(list(to_list_view(self.triples_NMU, node=True, path=True, value=True)), self.triples_NMU)
+
+    def test_agg_node(self):
+        self.assertListEqual(list(to_list_view(self.triples_111, node=False, path=True, value=True)),
+            [(ns.bse.iso, 123)])
+        self.assertListEqual(list(to_list_view(self.triples_11U, node=False, path=True, value=True)),
+            [(ns.bse.tag, 'tag#1234'), (ns.bse.tag, 'tag#5678')])
+        self.assertListEqual(list(to_list_view(self.triples_1M1, node=False, path=True, value=True)),
+            [(ns.bse.iso, 123), (ns.bse.t_created, '2010-01-02')])
+        self.assertListEqual(list(to_list_view(self.triples_1MU, node=False, path=True, value=True)),
+            [(ns.bse.iso, 123), (ns.bse.tag, 'tag#1234'), (ns.bse.tag, 'tag#5678')])
+        self.assertListEqual(list(to_list_view(self.triples_N11, node=False, path=True, value=True)),
+            [(ns.bse.iso, 123), (ns.bse.iso, 321)])
+        self.assertListEqual(list(to_list_view(self.triples_N1U, node=False, path=True, value=True)),
+            [(ns.bse.tag, 'tag#1234'), (ns.bse.tag, 'tag#5678'), (ns.bse.tag, 'tag#4321')])
+        self.assertListEqual(list(to_list_view(self.triples_NM1, node=False, path=True, value=True)),
+            [(ns.bse.iso, 123), (ns.bse.t_created, '2010-01-02'), (ns.bse.iso, 321), (ns.bse.t_created, '2022-02-22')])
+        self.assertListEqual(list(to_list_view(self.triples_NMU, node=False, path=True, value=True)),
+            [(ns.bse.iso, 123), (ns.bse.tag, 'tag#1234'), (ns.bse.tag, 'tag#5678'), (ns.bse.iso, 321), (ns.bse.t_created, '2022-02-22')])
+
+    def test_agg_path(self):
+        self.assertListEqual(list(to_list_view(self.triples_111, node=True, path=False, value=True)),
+            [('ent#1234', 123)])
+        self.assertListEqual(list(to_list_view(self.triples_11U, node=True, path=False, value=True)),
+            [('ent#1234', 'tag#1234'), ('ent#1234', 'tag#5678')])
+        self.assertListEqual(list(to_list_view(self.triples_1M1, node=True, path=False, value=True)),
+            [('ent#1234', 123), ('ent#1234', '2010-01-02')])
+        self.assertListEqual(list(to_list_view(self.triples_1MU, node=True, path=False, value=True)),
+            [('ent#1234', 123), ('ent#1234', 'tag#1234'), ('ent#1234', 'tag#5678')])
+        self.assertListEqual(list(to_list_view(self.triples_N11, node=True, path=False, value=True)),
+            [('ent#1234', 123), ('ent#4321', 321)])
+        self.assertListEqual(list(to_list_view(self.triples_N1U, node=True, path=False, value=True)),
+            [('ent#1234', 'tag#1234'), ('ent#1234', 'tag#5678'), ('ent#4321', 'tag#4321')])
+        self.assertListEqual(list(to_list_view(self.triples_NM1, node=True, path=False, value=True)),
+            [('ent#1234', 123), ('ent#1234', '2010-01-02'), ('ent#4321', 321), ('ent#4321', '2022-02-22')])
+        self.assertListEqual(list(to_list_view(self.triples_NMU, node=True, path=False, value=True)),
+            [('ent#1234', 123), ('ent#1234', 'tag#1234'), ('ent#1234', 'tag#5678'), ('ent#4321', 321), ('ent#4321', '2022-02-22')])
+
+    def test_agg_node_path(self):
+        self.assertListEqual(list(to_list_view(self.triples_111, node=False, path=False, value=True)),
+            [123])
+        self.assertListEqual(list(to_list_view(self.triples_11U, node=False, path=False, value=True)),
+            ['tag#1234', 'tag#5678'])
+        self.assertListEqual(list(to_list_view(self.triples_1M1, node=False, path=False, value=True)),
+            [123, '2010-01-02'])
+        self.assertListEqual(list(to_list_view(self.triples_1MU, node=False, path=False, value=True)),
+            [123, 'tag#1234', 'tag#5678'])
+        self.assertListEqual(list(to_list_view(self.triples_N11, node=False, path=False, value=True)),
+            [123, 321])
+        self.assertListEqual(list(to_list_view(self.triples_N1U, node=False, path=False, value=True)),
+            ['tag#1234', 'tag#5678', 'tag#4321'])
+        self.assertListEqual(list(to_list_view(self.triples_NM1, node=False, path=False, value=True)),
+            [123, '2010-01-02', 321, '2022-02-22'])
+        self.assertListEqual(list(to_list_view(self.triples_NMU, node=False, path=False, value=True)),
+            [123, 'tag#1234', 'tag#5678', 321, '2022-02-22'])
+
+    def test_agg_value(self):
+        # value flag has no effect
+        self.assertListEqual(list(to_list_view(self.triples_111, node=True, path=True, value=True)), self.triples_111)
+        self.assertListEqual(list(to_list_view(self.triples_11U, node=True, path=True, value=True)), self.triples_11U)
+        self.assertListEqual(list(to_list_view(self.triples_1M1, node=True, path=True, value=True)), self.triples_1M1)
+        self.assertListEqual(list(to_list_view(self.triples_1MU, node=True, path=True, value=True)), self.triples_1MU)
+        self.assertListEqual(list(to_list_view(self.triples_N11, node=True, path=True, value=True)), self.triples_N11)
+        self.assertListEqual(list(to_list_view(self.triples_N1U, node=True, path=True, value=True)), self.triples_N1U)
+        self.assertListEqual(list(to_list_view(self.triples_NM1, node=True, path=True, value=True)), self.triples_NM1)
+        self.assertListEqual(list(to_list_view(self.triples_NMU, node=True, path=True, value=True)), self.triples_NMU)
+
+    def test_agg_node_value(self):
+        # value flag has no effect -> same test as test_agg_node
+        self.assertListEqual(list(to_list_view(self.triples_111, node=False, path=True, value=False)),
+            [(ns.bse.iso, 123)])
+        self.assertListEqual(list(to_list_view(self.triples_11U, node=False, path=True, value=False)),
+            [(ns.bse.tag, 'tag#1234'), (ns.bse.tag, 'tag#5678')])
+        self.assertListEqual(list(to_list_view(self.triples_1M1, node=False, path=True, value=False)),
+            [(ns.bse.iso, 123), (ns.bse.t_created, '2010-01-02')])
+        self.assertListEqual(list(to_list_view(self.triples_1MU, node=False, path=True, value=False)),
+            [(ns.bse.iso, 123), (ns.bse.tag, 'tag#1234'), (ns.bse.tag, 'tag#5678')])
+        self.assertListEqual(list(to_list_view(self.triples_N11, node=False, path=True, value=False)),
+            [(ns.bse.iso, 123), (ns.bse.iso, 321)])
+        self.assertListEqual(list(to_list_view(self.triples_N1U, node=False, path=True, value=False)),
+            [(ns.bse.tag, 'tag#1234'), (ns.bse.tag, 'tag#5678'), (ns.bse.tag, 'tag#4321')])
+        self.assertListEqual(list(to_list_view(self.triples_NM1, node=False, path=True, value=False)),
+            [(ns.bse.iso, 123), (ns.bse.t_created, '2010-01-02'), (ns.bse.iso, 321), (ns.bse.t_created, '2022-02-22')])
+        self.assertListEqual(list(to_list_view(self.triples_NMU, node=False, path=True, value=False)),
+            [(ns.bse.iso, 123), (ns.bse.tag, 'tag#1234'), (ns.bse.tag, 'tag#5678'), (ns.bse.iso, 321), (ns.bse.t_created, '2022-02-22')])
+
+    def test_agg_path_value(self):
+        # value flag has no effect -> same test as test_agg_path
+        self.assertListEqual(list(to_list_view(self.triples_111, node=True, path=False, value=False)),
+            [('ent#1234', 123)])
+        self.assertListEqual(list(to_list_view(self.triples_11U, node=True, path=False, value=False)),
+            [('ent#1234', 'tag#1234'), ('ent#1234', 'tag#5678')])
+        self.assertListEqual(list(to_list_view(self.triples_1M1, node=True, path=False, value=False)),
+            [('ent#1234', 123), ('ent#1234', '2010-01-02')])
+        self.assertListEqual(list(to_list_view(self.triples_1MU, node=True, path=False, value=False)),
+            [('ent#1234', 123), ('ent#1234', 'tag#1234'), ('ent#1234', 'tag#5678')])
+        self.assertListEqual(list(to_list_view(self.triples_N11, node=True, path=False, value=False)),
+            [('ent#1234', 123), ('ent#4321', 321)])
+        self.assertListEqual(list(to_list_view(self.triples_N1U, node=True, path=False, value=False)),
+            [('ent#1234', 'tag#1234'), ('ent#1234', 'tag#5678'), ('ent#4321', 'tag#4321')])
+        self.assertListEqual(list(to_list_view(self.triples_NM1, node=True, path=False, value=False)),
+            [('ent#1234', 123), ('ent#1234', '2010-01-02'), ('ent#4321', 321), ('ent#4321', '2022-02-22')])
+        self.assertListEqual(list(to_list_view(self.triples_NMU, node=True, path=False, value=False)),
+            [('ent#1234', 123), ('ent#1234', 'tag#1234'), ('ent#1234', 'tag#5678'), ('ent#4321', 321), ('ent#4321', '2022-02-22')])
+
+    def test_agg_all(self):
+        # value flag has no effect -> same test as test_agg_node_path
+        self.assertListEqual(list(to_list_view(self.triples_111, node=False, path=False, value=False)),
+            [123])
+        self.assertListEqual(list(to_list_view(self.triples_11U, node=False, path=False, value=False)),
+            ['tag#1234', 'tag#5678'])
+        self.assertListEqual(list(to_list_view(self.triples_1M1, node=False, path=False, value=False)),
+            [123, '2010-01-02'])
+        self.assertListEqual(list(to_list_view(self.triples_1MU, node=False, path=False, value=False)),
+            [123, 'tag#1234', 'tag#5678'])
+        self.assertListEqual(list(to_list_view(self.triples_N11, node=False, path=False, value=False)),
+            [123, 321])
+        self.assertListEqual(list(to_list_view(self.triples_N1U, node=False, path=False, value=False)),
+            ['tag#1234', 'tag#5678', 'tag#4321'])
+        self.assertListEqual(list(to_list_view(self.triples_NM1, node=False, path=False, value=False)),
+            [123, '2010-01-02', 321, '2022-02-22'])
+        self.assertListEqual(list(to_list_view(self.triples_NMU, node=False, path=False, value=False)),
+            [123, 'tag#1234', 'tag#5678', 321, '2022-02-22'])
+
+
+class TestDictView(unittest.TestCase):
+    def setUp(self):
+        self.unique_paths = {ns.bse.iso, ns.bse.t_created}
+        self.triples_111 = [('ent#1234', ns.bse.iso, 123)]
+        self.triples_11U = [('ent#1234', ns.bse.tag, 'tag#1234'),
+                            ('ent#1234', ns.bse.tag, 'tag#5678')]
+        self.triples_1M1 = [('ent#1234', ns.bse.iso, 123),
+                            ('ent#1234', ns.bse.t_created, '2010-01-02')]
+        self.triples_1MU = [('ent#1234', ns.bse.iso, 123),
+                            ('ent#1234', ns.bse.tag, 'tag#1234'),
+                            ('ent#1234', ns.bse.tag, 'tag#5678')]
+        self.triples_N11 = [('ent#1234', ns.bse.iso, 123),
+                            ('ent#4321', ns.bse.iso, 321)]
+        self.triples_N1U = [('ent#1234', ns.bse.tag, 'tag#1234'),
+                            ('ent#1234', ns.bse.tag, 'tag#5678'),
+                            ('ent#4321', ns.bse.tag, 'tag#4321')]
+        self.triples_NM1 = [('ent#1234', ns.bse.iso, 123),
+                            ('ent#1234', ns.bse.t_created, '2010-01-02'),
+                            ('ent#4321', ns.bse.iso, 321),
+                            ('ent#4321', ns.bse.t_created, '2022-02-22')]
+        self.triples_NMU = [('ent#1234', ns.bse.iso, 123),
+                            ('ent#1234', ns.bse.tag, 'tag#1234'),
+                            ('ent#1234', ns.bse.tag, 'tag#5678'),
+                            ('ent#4321', ns.bse.iso, 321),
+                            ('ent#4321', ns.bse.t_created, '2022-02-22')]
+
+    def test_errounous_call(self):
+        # return set instead of value
+        self.assertSetEqual(to_dict_view(self.triples_111, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=False),
+            {123})
+        self.assertSetEqual(to_dict_view(self.triples_111, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=False, path=False, value=False),
+            {123})
+        # one_node mismatch: return set of values instead of value
+        self.assertDictEqual(to_dict_view(self.triples_111, one_node=False, one_path=True, unique_paths=self.unique_paths, node=False, path=True, value=False),
+            {ns.bse.iso: {123}})
+        # one_path mismatch: return set of values instead of value
+        self.assertDictEqual(to_dict_view(self.triples_111, one_node=True, one_path=False, unique_paths=self.unique_paths, node=True, path=False, value=False),
+            {'ent#1234': {123}})
+        # unique_paths mismatch: return set of values instead of value
+        self.assertSetEqual(to_dict_view(self.triples_111, one_node=True, one_path=False, unique_paths={}, node=False, path=False, value=False),
+            {123})
+        self.assertDictEqual(to_dict_view(self.triples_111, one_node=True, one_path=False, unique_paths={}, node=False, path=True, value=False),
+            {ns.bse.iso: {123}})
+        self.assertDictEqual(to_dict_view(self.triples_111, one_node=True, one_path=False, unique_paths={}, node=True, path=False, value=False),
+            {'ent#1234': {123}})
+        self.assertDictEqual(to_dict_view(self.triples_111, one_node=True, one_path=False, unique_paths={}, node=True, path=True, value=False),
+            {'ent#1234': {ns.bse.iso: {123}}})
+
+    def test_agg_none(self):
+        self.assertDictEqual(to_dict_view(self.triples_111, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=True, path=True, value=True),
+            {'ent#1234': {ns.bse.iso: {123}}})
+        self.assertDictEqual(to_dict_view(self.triples_11U, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=True, path=True, value=True),
+            {'ent#1234': {ns.bse.tag: {'tag#1234', 'tag#5678'}}})
+        self.assertDictEqual(to_dict_view(self.triples_1M1, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=True, path=True, value=True),
+            {'ent#1234': {ns.bse.iso: {123}, ns.bse.t_created: {'2010-01-02'}}})
+        self.assertDictEqual(to_dict_view(self.triples_1MU, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=True, path=True, value=True),
+            {'ent#1234': {ns.bse.iso: {123}, ns.bse.tag: {'tag#1234', 'tag#5678'}}})
+        self.assertDictEqual(to_dict_view(self.triples_N11, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=True, path=True, value=True),
+            {'ent#1234': {ns.bse.iso: {123}}, 'ent#4321': {ns.bse.iso: {321}}})
+        self.assertDictEqual(to_dict_view(self.triples_N1U, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=True, path=True, value=True),
+            {'ent#1234': {ns.bse.tag: {'tag#1234', 'tag#5678'}}, 'ent#4321': {ns.bse.tag: {'tag#4321'}}})
+        self.assertDictEqual(to_dict_view(self.triples_NM1, one_node=False, one_path=False, unique_paths=self.unique_paths, node=True, path=True, value=True),
+            {'ent#1234': {ns.bse.iso: {123}, ns.bse.t_created: {'2010-01-02'}}, 'ent#4321': {ns.bse.iso: {321}, ns.bse.t_created: {'2022-02-22'}}})
+        self.assertDictEqual(to_dict_view(self.triples_NMU, one_node=False, one_path=False, unique_paths=self.unique_paths, node=True, path=True, value=True),
+            {'ent#1234': {ns.bse.iso: {123}, ns.bse.tag: {'tag#1234', 'tag#5678'}}, 'ent#4321': {ns.bse.iso: {321}, ns.bse.t_created: {'2022-02-22'}}})
+        # empty
+        self.assertDictEqual(to_dict_view([], one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=True, path=True, value=True), {})
+        self.assertDictEqual(to_dict_view([], one_node=True,  one_path=False, unique_paths=self.unique_paths, node=True, path=True, value=True), {})
+        self.assertDictEqual(to_dict_view([], one_node=False, one_path=True,  unique_paths=self.unique_paths, node=True, path=True, value=True), {})
+        self.assertDictEqual(to_dict_view([], one_node=False, one_path=False, unique_paths=self.unique_paths, node=True, path=True, value=True), {})
+
+    def test_agg_node(self):
+        self.assertDictEqual(to_dict_view(self.triples_111, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=False, path=True, value=True),
+            {ns.bse.iso: {123}})
+        self.assertDictEqual(to_dict_view(self.triples_11U, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=False, path=True, value=True),
+            {ns.bse.tag: {'tag#1234', 'tag#5678'}})
+        self.assertDictEqual(to_dict_view(self.triples_1M1, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=False, path=True, value=True),
+            {ns.bse.iso: {123}, ns.bse.t_created: {'2010-01-02'}})
+        self.assertDictEqual(to_dict_view(self.triples_1MU, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=False, path=True, value=True),
+            {ns.bse.iso: {123}, ns.bse.tag: {'tag#1234', 'tag#5678'}})
+        self.assertDictEqual(to_dict_view(self.triples_N11, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=False, path=True, value=True),
+            {ns.bse.iso: {123, 321}})
+        self.assertDictEqual(to_dict_view(self.triples_N1U, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=False, path=True, value=True),
+            {ns.bse.tag: {'tag#1234', 'tag#5678', 'tag#4321'}})
+        self.assertDictEqual(to_dict_view(self.triples_NM1, one_node=False, one_path=False, unique_paths=self.unique_paths, node=False, path=True, value=True),
+            {ns.bse.iso: {123, 321}, ns.bse.t_created: {'2010-01-02', '2022-02-22'}})
+        self.assertDictEqual(to_dict_view(self.triples_NMU, one_node=False, one_path=False, unique_paths=self.unique_paths, node=False, path=True, value=True),
+            {ns.bse.iso: {123, 321}, ns.bse.tag: {'tag#1234', 'tag#5678'}, ns.bse.t_created: {'2022-02-22'}})
+        # empty
+        self.assertDictEqual(to_dict_view([], one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=False, path=True, value=True), {})
+        self.assertDictEqual(to_dict_view([], one_node=True,  one_path=False, unique_paths=self.unique_paths, node=False, path=True, value=True), {})
+        self.assertDictEqual(to_dict_view([], one_node=False, one_path=True,  unique_paths=self.unique_paths, node=False, path=True, value=True), {})
+        self.assertDictEqual(to_dict_view([], one_node=False, one_path=False, unique_paths=self.unique_paths, node=False, path=True, value=True), {})
+
+    def test_agg_path(self):
+        self.assertDictEqual(to_dict_view(self.triples_111, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=True, path=False, value=True),
+            {'ent#1234': {123}})
+        self.assertDictEqual(to_dict_view(self.triples_11U, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=True, path=False, value=True),
+            {'ent#1234': {'tag#1234', 'tag#5678'}})
+        self.assertDictEqual(to_dict_view(self.triples_1M1, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=True, path=False, value=True),
+            {'ent#1234': {123, '2010-01-02'}})
+        self.assertDictEqual(to_dict_view(self.triples_1MU, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=True, path=False, value=True),
+            {'ent#1234': {123, 'tag#1234', 'tag#5678'}})
+        self.assertDictEqual(to_dict_view(self.triples_N11, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=True, path=False, value=True),
+            {'ent#1234': {123}, 'ent#4321': {321}})
+        self.assertDictEqual(to_dict_view(self.triples_N1U, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=True, path=False, value=True),
+            {'ent#1234': {'tag#1234', 'tag#5678'}, 'ent#4321': {'tag#4321'}})
+        self.assertDictEqual(to_dict_view(self.triples_NM1, one_node=False, one_path=False, unique_paths=self.unique_paths, node=True, path=False, value=True),
+            {'ent#1234': {123, '2010-01-02'}, 'ent#4321': {321, '2022-02-22'}})
+        self.assertDictEqual(to_dict_view(self.triples_NMU, one_node=False, one_path=False, unique_paths=self.unique_paths, node=True, path=False, value=True),
+            {'ent#1234': {123, 'tag#1234', 'tag#5678'}, 'ent#4321': {321, '2022-02-22'}})
+        # empty
+        self.assertDictEqual(to_dict_view([], one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=True, path=False, value=True), {})
+        self.assertDictEqual(to_dict_view([], one_node=True,  one_path=False, unique_paths=self.unique_paths, node=True, path=False, value=True), {})
+        self.assertDictEqual(to_dict_view([], one_node=False, one_path=True,  unique_paths=self.unique_paths, node=True, path=False, value=True), {})
+        self.assertDictEqual(to_dict_view([], one_node=False, one_path=False, unique_paths=self.unique_paths, node=True, path=False, value=True), {})
+
+    def test_agg_node_path(self):
+        self.assertSetEqual(to_dict_view(self.triples_111, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=True),
+            {123})
+        self.assertSetEqual(to_dict_view(self.triples_11U, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=True),
+            {'tag#1234', 'tag#5678'})
+        self.assertSetEqual(to_dict_view(self.triples_1M1, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=False, path=False, value=True),
+            {123, '2010-01-02'})
+        self.assertSetEqual(to_dict_view(self.triples_1MU, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=False, path=False, value=True),
+            {123, 'tag#1234', 'tag#5678'})
+        self.assertSetEqual(to_dict_view(self.triples_N11, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=True),
+            {123, 321})
+        self.assertSetEqual(to_dict_view(self.triples_N1U, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=True),
+            {'tag#1234', 'tag#5678', 'tag#4321'})
+        self.assertSetEqual(to_dict_view(self.triples_NM1, one_node=False, one_path=False, unique_paths=self.unique_paths, node=False, path=False, value=True),
+            {123, '2010-01-02', 321, '2022-02-22'})
+        self.assertSetEqual(to_dict_view(self.triples_NMU, one_node=False, one_path=False, unique_paths=self.unique_paths, node=False, path=False, value=True),
+            {123, 'tag#1234', 'tag#5678', 321, '2022-02-22'})
+        # empty
+        self.assertSetEqual(to_dict_view([], one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=True), set())
+        self.assertSetEqual(to_dict_view([], one_node=True,  one_path=False, unique_paths=self.unique_paths, node=False, path=False, value=True), set())
+        self.assertSetEqual(to_dict_view([], one_node=False, one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=True), set())
+        self.assertSetEqual(to_dict_view([], one_node=False, one_path=False, unique_paths=self.unique_paths, node=False, path=False, value=True), set())
+
+    def test_agg_value(self):
+        self.assertDictEqual(to_dict_view(self.triples_111, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=True, path=True, value=False),
+            {'ent#1234': {ns.bse.iso: 123}})
+        self.assertDictEqual(to_dict_view(self.triples_11U, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=True, path=True, value=False),
+            {'ent#1234': {ns.bse.tag: {'tag#1234', 'tag#5678'}}})
+        self.assertDictEqual(to_dict_view(self.triples_1M1, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=True, path=True, value=False),
+            {'ent#1234': {ns.bse.iso: 123, ns.bse.t_created: '2010-01-02'}})
+        self.assertDictEqual(to_dict_view(self.triples_1MU, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=True, path=True, value=False),
+            {'ent#1234': {ns.bse.iso: 123, ns.bse.tag: {'tag#1234', 'tag#5678'}}})
+        self.assertDictEqual(to_dict_view(self.triples_N11, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=True, path=True, value=False),
+            {'ent#1234': {ns.bse.iso: 123}, 'ent#4321': {ns.bse.iso: 321}})
+        self.assertDictEqual(to_dict_view(self.triples_N1U, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=True, path=True, value=False),
+            {'ent#1234': {ns.bse.tag: {'tag#1234', 'tag#5678'}}, 'ent#4321': {ns.bse.tag: {'tag#4321'}}})
+        self.assertDictEqual(to_dict_view(self.triples_NM1, one_node=False, one_path=False, unique_paths=self.unique_paths, node=True, path=True, value=False),
+            {'ent#1234': {ns.bse.iso: 123, ns.bse.t_created: '2010-01-02'}, 'ent#4321': {ns.bse.iso: 321, ns.bse.t_created: '2022-02-22'}})
+        self.assertDictEqual(to_dict_view(self.triples_NMU, one_node=False, one_path=False, unique_paths=self.unique_paths, node=True, path=True, value=False),
+            {'ent#1234': {ns.bse.iso: 123, ns.bse.tag: {'tag#1234', 'tag#5678'}}, 'ent#4321': {ns.bse.iso: 321, ns.bse.t_created: '2022-02-22'}})
+        # empty
+        self.assertDictEqual(to_dict_view([], one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=True, path=True, value=False), {})
+        self.assertDictEqual(to_dict_view([], one_node=True,  one_path=False, unique_paths=self.unique_paths, node=True, path=True, value=False), {})
+        self.assertDictEqual(to_dict_view([], one_node=False, one_path=True,  unique_paths=self.unique_paths, node=True, path=True, value=False), {})
+        self.assertDictEqual(to_dict_view([], one_node=False, one_path=False, unique_paths=self.unique_paths, node=True, path=True, value=False), {})
+
+    def test_agg_node_value(self):
+        self.assertDictEqual(to_dict_view(self.triples_111, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=False, path=True, value=False),
+            {ns.bse.iso: 123})
+        self.assertDictEqual(to_dict_view(self.triples_11U, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=False, path=True, value=False),
+            {ns.bse.tag: {'tag#1234', 'tag#5678'}})
+        self.assertDictEqual(to_dict_view(self.triples_1M1, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=False, path=True, value=False),
+            {ns.bse.iso: 123, ns.bse.t_created: '2010-01-02'})
+        self.assertDictEqual(to_dict_view(self.triples_1MU, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=False, path=True, value=False),
+            {ns.bse.iso: 123, ns.bse.tag: {'tag#1234', 'tag#5678'}})
+        self.assertDictEqual(to_dict_view(self.triples_N11, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=False, path=True, value=False),
+            {ns.bse.iso: {123, 321}})
+        self.assertDictEqual(to_dict_view(self.triples_N1U, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=False, path=True, value=False),
+            {ns.bse.tag: {'tag#1234', 'tag#5678', 'tag#4321'}})
+        self.assertDictEqual(to_dict_view(self.triples_NM1, one_node=False, one_path=False, unique_paths=self.unique_paths, node=False, path=True, value=False),
+            {ns.bse.iso: {123, 321}, ns.bse.t_created: {'2010-01-02', '2022-02-22'}})
+        self.assertDictEqual(to_dict_view(self.triples_NMU, one_node=False, one_path=False, unique_paths=self.unique_paths, node=False, path=True, value=False),
+            {ns.bse.iso: {123, 321}, ns.bse.tag: {'tag#1234', 'tag#5678'}, ns.bse.t_created: {'2022-02-22'}})
+        # empty
+        self.assertDictEqual(to_dict_view([], one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=False, path=True, value=False), {})
+        self.assertDictEqual(to_dict_view([], one_node=True,  one_path=False, unique_paths=self.unique_paths, node=False, path=True, value=False), {})
+        self.assertDictEqual(to_dict_view([], one_node=False, one_path=True,  unique_paths=self.unique_paths, node=False, path=True, value=False), {})
+        self.assertDictEqual(to_dict_view([], one_node=False, one_path=False, unique_paths=self.unique_paths, node=False, path=True, value=False), {})
+
+    def test_agg_path_value(self):
+        self.assertDictEqual(to_dict_view(self.triples_111, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=True, path=False, value=False),
+            {'ent#1234': 123})
+        self.assertDictEqual(to_dict_view(self.triples_11U, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=True, path=False, value=False),
+            {'ent#1234': {'tag#1234', 'tag#5678'}})
+        self.assertDictEqual(to_dict_view(self.triples_1M1, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=True, path=False, value=False),
+            {'ent#1234': {123, '2010-01-02'}})
+        self.assertDictEqual(to_dict_view(self.triples_1MU, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=True, path=False, value=False),
+            {'ent#1234': {123, 'tag#1234', 'tag#5678'}})
+        self.assertDictEqual(to_dict_view(self.triples_N11, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=True, path=False, value=False),
+            {'ent#1234': 123, 'ent#4321': 321})
+        self.assertDictEqual(to_dict_view(self.triples_N1U, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=True, path=False, value=False),
+            {'ent#1234': {'tag#1234', 'tag#5678'}, 'ent#4321': {'tag#4321'}})
+        self.assertDictEqual(to_dict_view(self.triples_NM1, one_node=False, one_path=False, unique_paths=self.unique_paths, node=True, path=False, value=False),
+            {'ent#1234': {123, '2010-01-02'}, 'ent#4321': {321, '2022-02-22'}})
+        self.assertDictEqual(to_dict_view(self.triples_NMU, one_node=False, one_path=False, unique_paths=self.unique_paths, node=True, path=False, value=False),
+            {'ent#1234': {123, 'tag#1234', 'tag#5678'}, 'ent#4321': {321, '2022-02-22'}})
+        # empty
+        self.assertDictEqual(to_dict_view([], one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=True, path=False, value=False), {})
+        self.assertDictEqual(to_dict_view([], one_node=True,  one_path=False, unique_paths=self.unique_paths, node=True, path=False, value=False), {})
+        self.assertDictEqual(to_dict_view([], one_node=False, one_path=True,  unique_paths=self.unique_paths, node=True, path=False, value=False), {})
+        self.assertDictEqual(to_dict_view([], one_node=False, one_path=False, unique_paths=self.unique_paths, node=True, path=False, value=False), {})
+
+    def test_agg_all(self):
+        self.assertEqual(to_dict_view(self.triples_111, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=False),
+            123)
+        self.assertSetEqual(to_dict_view(self.triples_11U, one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=False),
+            {'tag#1234', 'tag#5678'})
+        self.assertSetEqual(to_dict_view(self.triples_1M1, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=False, path=False, value=False),
+            {123, '2010-01-02'})
+        self.assertSetEqual(to_dict_view(self.triples_1MU, one_node=True,  one_path=False, unique_paths=self.unique_paths, node=False, path=False, value=False),
+            {123, 'tag#1234', 'tag#5678'})
+        self.assertSetEqual(to_dict_view(self.triples_N11, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=False),
+            {123, 321})
+        self.assertSetEqual(to_dict_view(self.triples_N1U, one_node=False, one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=False),
+            {'tag#1234', 'tag#5678', 'tag#4321'})
+        self.assertSetEqual(to_dict_view(self.triples_NM1, one_node=False, one_path=False, unique_paths=self.unique_paths, node=False, path=False, value=False),
+            {123, '2010-01-02', 321, '2022-02-22'})
+        self.assertSetEqual(to_dict_view(self.triples_NMU, one_node=False, one_path=False, unique_paths=self.unique_paths, node=False, path=False, value=False),
+            {123, 'tag#1234', 'tag#5678', 321, '2022-02-22'})
+        # empty
+        self.assertEqual(to_dict_view([], one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=False), None)
+        self.assertSetEqual(to_dict_view([], one_node=True,  one_path=False, unique_paths=self.unique_paths, node=False, path=False, value=False), set())
+        self.assertSetEqual(to_dict_view([], one_node=False, one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=False), set())
+        self.assertSetEqual(to_dict_view([], one_node=False, one_path=False, unique_paths=self.unique_paths, node=False, path=False, value=False), set())
+        self.assertEqual(to_dict_view([], one_node=True,  one_path=True,  unique_paths=self.unique_paths, node=False, path=False, value=False, default=123), 123)
+
+## main ##
+
+if __name__ == '__main__':
+    unittest.main()
+
+## EOF ##
diff --git a/test/graph/test_walk.py b/test/graph/test_walk.py
new file mode 100644
index 0000000..4b844da
--- /dev/null
+++ b/test/graph/test_walk.py
@@ -0,0 +1,170 @@
+
+# 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
+
+# symbol to test
+from bsfs.graph.walk import Walk
+
+## code ##
+
+ns.bse = ns.bsfs.Entity()
+ns.bst = ns.bsfs.Tag()
+
+class TestWalk(unittest.TestCase):
+    def setUp(self):
+        # backend setup
+        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: <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 .
+            bsfs:User rdfs:subClassOf bsfs:Node .
+            xsd:string rdfs:subClassOf bsfs:Literal .
+
+            bse:author rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Node ;
+                rdfs:range bsfs:User .
+
+            bse:tag rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range bsfs:Tag .
+
+            bst:label rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Tag ;
+                rdfs:range xsd:string ;
+                bsfs:unique "true"^^xsd:boolean .
+
+            bst:subTagOf rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Tag ;
+                rdfs:range bsfs:Tag .
+
+            bst:main rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Tag ;
+                rdfs:range bsfs:Entity .
+
+            bst:author rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Tag ;
+                rdfs:range xsd:string .
+
+            ''')
+        self.backend = SparqlStore.Open()
+        self.user = URI('http://example.com/me')
+        self.ac = NullAC(self.backend, self.user)
+        self.graph = Graph(self.backend, self.ac)
+        self.graph.migrate(self.schema)
+
+        # nodes setup
+        self.ents = self.graph.nodes(ns.bsfs.Entity, {
+            URI('http://example.com/me/entity#1234'),
+            URI('http://example.com/me/entity#4321')})
+        self.tags = self.graph.nodes(ns.bsfs.Tag, {
+            URI('http://example.com/me/tag#1234'),
+            URI('http://example.com/me/tag#4321')})
+        # add some instances
+        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(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])))
+        # comparison respects type
+        class Foo(Walk): pass
+        self.assertNotEqual(Walk(self.ents, [p_tag]), Foo(self.ents, [p_tag]))
+        self.assertNotEqual(hash(Walk(self.ents, [p_tag])), hash(Foo(self.ents, [p_tag])))
+        # comparison respects root
+        self.assertNotEqual(Walk(self.ents, [p_author]), Walk(self.tags, [p_author]))
+        self.assertNotEqual(hash(Walk(self.ents, [p_author])), hash(Walk(self.tags, [p_author])))
+        # comparison respects path
+        self.assertNotEqual(Walk(self.tags, [p_author]), Walk(self.tags, [p_main]))
+        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(@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(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(ns.bse.tag),
+            )).tail,
+            self.schema.node(ns.bsfs.Tag))
+        self.assertEqual(Walk(self.ents, (
+            self.schema.predicate(ns.bse.tag),
+            self.schema.predicate(ns.bst.main),
+            )).tail,
+            self.schema.node(ns.bsfs.Entity))
+
+    def test_step(self):
+        tag_type = self.schema.node(ns.bsfs.Tag)
+        # step returns a predicate
+        self.assertEqual(Walk.step(self.schema, tag_type, '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(ns.bse.tag), ))
+        # first step
+        self.assertEqual(walk.subTagOf, Walk(self.ents, (
+            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(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')
+        # ambiguous step raises an error
+        self.assertRaises(ValueError, getattr, walk, 'author')
+
+    def test_get(self): # get, __call__
+        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'))}
+        # get returns from Nodes.get
+        self.assertDictEqual(walk.get(), {
+            self.graph.node(ns.bsfs.Entity, URI('http://example.com/me/entity#1234')): tags,
+            self.graph.node(ns.bsfs.Entity, URI('http://example.com/me/entity#4321')): tags,
+            })
+        self.assertDictEqual(walk(), {
+            self.graph.node(ns.bsfs.Entity, URI('http://example.com/me/entity#1234')): tags,
+            self.graph.node(ns.bsfs.Entity, URI('http://example.com/me/entity#4321')): tags,
+            })
+        # get passes kwargs to Nodes.get
+        self.assertSetEqual(tags, walk.get(node=False))
+        self.assertSetEqual(tags, walk(node=False))
+        self.assertSetEqual(tags, set(walk.get(view=list, node=False)))
+        self.assertSetEqual(tags, set(walk(view=list, node=False)))
+        # get returns values if need be
+        self.assertSetEqual(walk.label(node=False), {'hello', 'world'})
+
+
+## main ##
+
+if __name__ == '__main__':
+    unittest.main()
+
+## EOF ##