Feature support in the schema

* Type annotations
* Feature type
* Moved from_string from Schema to its own file/function
* Root predicate has a valid (not-None) range
* ROOT_... export in schema.types
* Empty as the default Schema constructor
* Schema loads some additional default symbols
* _Type instances compare along class hierarchy

1 files changed, 1007 insertions, 0 deletions

diff --git a/test/schema/test_serialize.py b/test/schema/test_serialize.py
new file mode 100644
index 0000000..7392cc0
--- /dev/null
+++ b/test/schema/test_serialize.py
@@ -0,0 +1,1007 @@
+"""
+
+Part of the tagit test suite.
+A copy of the license is provided with the project.
+Author: Matthias Baumgartner, 2022
+"""
+# imports
+import unittest
+
+# bsfs imports
+from bsfs.namespace import ns
+from bsfs.schema import Schema, types
+from bsfs.utils import errors, URI
+
+# objects to test
+from bsfs.schema.serialize import from_string, to_string
+
+
+## code ##
+
+class TestFromString(unittest.TestCase):
+
+    def test_empty(self):
+        # schema contains at least the root types
+        self.assertEqual(from_string(''), Schema())
+
+
+    def test_circular_dependency(self):
+        # must not have circular dependencies
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            # ah, a nice circular dependency
+            bsfs:Entity rdfs:subClassOf bsfs:Document .
+            bsfs:Document rdfs:subClassOf bsfs:Entity .
+            bsfs:PDF rdfs:subClassOf bsfs:Document .
+            ''')
+
+
+    def test_node(self):
+        # all nodes must be defined
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            xsd:string rdfs:subClassOf bsfs:Literal .
+
+            bse:filename rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range xsd:string ;
+                bsfs:unique "false"^^xsd:boolean .
+            ''')
+
+        # node definitions must be consistent (cannot re-use a node uri)
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            bsfs:Document rdfs:subClassOf bsfs:Node .
+            bsfs:Document rdfs:subClassOf bsfs:Entity . # conflicting parent
+            ''')
+
+        # additional nodes can be defined
+        n_unused = types.ROOT_NODE.get_child(ns.bsfs.unused)
+        self.assertEqual(Schema({}, {n_unused}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:unused rdfs:subClassOf bsfs:Node . # unused symbol
+            '''))
+
+        # a node can have multiple children
+        n_ent = types.ROOT_NODE.get_child(ns.bsfs.Entity)
+        n_tag = types.ROOT_NODE.get_child(ns.bsfs.Tag)
+        n_doc = n_ent.get_child(ns.bsfs.Document)
+        n_image = n_ent.get_child(ns.bsfs.Image)
+        self.assertEqual(Schema({}, {n_ent, n_tag, n_doc, n_image}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            # nodes inherit from same parent
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            bsfs:Tag rdfs:subClassOf bsfs:Node .
+
+            # nodes inherit from same parent
+            bsfs:Document rdfs:subClassOf bsfs:Entity .
+            bsfs:Image rdfs:subClassOf bsfs:Entity .
+            '''))
+
+        # additional nodes can be defined and used
+        n_ent = types.ROOT_NODE.get_child(ns.bsfs.Entity)
+        l_string = types.ROOT_LITERAL.get_child(ns.xsd.string)
+        p_filename = types.ROOT_PREDICATE.get_child(ns.bse.filename,
+            n_ent, l_string, False)
+        self.assertEqual(Schema({p_filename}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            xsd:string rdfs:subClassOf bsfs:Literal .
+
+            bse:filename rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range xsd:string ;
+                bsfs:unique "false"^^xsd:boolean .
+            '''))
+
+        # nodes can have annotations
+        self.assertDictEqual(from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            ''').node(ns.bsfs.Entity).annotations, {})
+        self.assertDictEqual(from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node ;
+                rdfs:label "hello world"^^xsd:string ;
+                bsfs:foo "1234"^^xsd:integer .
+
+            ''').node(ns.bsfs.Entity).annotations, {
+            ns.rdfs.label: 'hello world',
+            ns.bsfs.foo: 1234,
+            })
+
+
+    def test_literal(self):
+        # all literals must be defined
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:filename rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range xsd:string ; # undefined symbol
+                bsfs:unique "false"^^xsd:boolean .
+            ''')
+
+        # literal definitions must be consistent (cannot re-use a literal uri)
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+
+            xsd:string rdfs:subClassOf bsfs:Literal .
+            xsd:name rdfs:subClassOf bsfs:Literal .
+            xsd:name rdfs:subClassOf xsd:string . # conflicting parent
+            ''')
+
+        # additional literals can be defined
+        l_unused = types.ROOT_LITERAL.get_child(ns.xsd.unused)
+        self.assertEqual(Schema({}, {}, {l_unused}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            xsd:unused rdfs:subClassOf bsfs:Literal . # unused symbol
+            '''))
+
+        # a literal can have multiple children
+        l_string = types.ROOT_LITERAL.get_child(ns.xsd.string)
+        l_integer = types.ROOT_LITERAL.get_child(ns.xsd.integer)
+        l_unsigned = l_integer.get_child(ns.xsd.unsigned)
+        l_signed = l_integer.get_child(ns.xsd.signed)
+        self.assertEqual(Schema({}, {}, {l_string, l_integer, l_unsigned, l_signed}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            # literals inherit from same parent
+            xsd:string rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsfs:Literal .
+
+            # literals inherit from same parent
+            xsd:unsigned rdfs:subClassOf xsd:integer .
+            xsd:signed rdfs:subClassOf xsd:integer .
+            '''))
+
+        # additional literals can be defined and used
+        n_ent = types.ROOT_NODE.get_child(ns.bsfs.Entity)
+        l_string = types.ROOT_LITERAL.get_child(ns.xsd.string)
+        p_filename = types.ROOT_PREDICATE.get_child(ns.bse.filename,
+            n_ent, l_string, False)
+        self.assertEqual(Schema({p_filename}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            xsd:string rdfs:subClassOf bsfs:Literal .
+
+            bse:filename rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range xsd:string ;
+                bsfs:unique "false"^^xsd:boolean .
+            '''))
+
+        # literals can have annotations
+        self.assertDictEqual(from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+
+            xsd:string rdfs:subClassOf bsfs:Literal .
+
+            ''').literal(ns.xsd.string).annotations, {})
+        self.assertDictEqual(from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+
+            xsd:string rdfs:subClassOf bsfs:Literal ;
+                rdfs:label "hello world"^^xsd:string ;
+                bsfs:foo "1234"^^xsd:integer .
+
+            ''').literal(ns.xsd.string).annotations, {
+            ns.rdfs.label: 'hello world',
+            ns.bsfs.foo: 1234,
+            })
+
+
+    def test_predicate(self):
+        # domain must be defined
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            xsd:string rdfs:subClassOf bsfs:Literal .
+
+            bse:filename rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ; # undefined symbol
+                rdfs:range xsd:string ;
+                bsfs:unique "false"^^xsd:boolean .
+            ''')
+        # domain cannot be a literal
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Literal .
+            xsd:string rdfs:subClassOf bsfs:Literal .
+
+            bse:filename rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ; # literal instead of node
+                rdfs:range xsd:string ;
+                bsfs:unique "false"^^xsd:boolean .
+            ''')
+
+        # range must be defined
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:filename rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range xsd:string ; # undefined symbol
+                bsfs:unique "false"^^xsd:boolean .
+            ''')
+        # range must be defined
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:filename rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range bsfs:Foo ; # undefined symbol
+                bsfs:unique "false"^^xsd:boolean .
+            ''')
+        # range must be a node or a literal
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:filename rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range bsfs:Predicate ; # invalid symbol
+                bsfs:unique "false"^^xsd:boolean .
+            ''')
+
+        # additional predicates can be defined
+        n_ent = types.ROOT_NODE.get_child(ns.bsfs.Entity)
+        l_string = types.ROOT_LITERAL.get_child(ns.xsd.string)
+        p_comment = types.ROOT_PREDICATE.get_child(ns.bse.comment, domain=n_ent, range=l_string, unique=False)
+        self.assertEqual(Schema({p_comment}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            xsd:string rdfs:subClassOf bsfs:Literal .
+
+            bse:comment rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range xsd:string ;
+                bsfs:unique "false"^^xsd:boolean .
+            '''))
+
+        # predicates inherit properties from parents
+        n_ent = types.ROOT_NODE.get_child(ns.bsfs.Entity)
+        l_string = types.ROOT_LITERAL.get_child(ns.xsd.string)
+        p_annotation = types.ROOT_PREDICATE.get_child(ns.bsfs.Annotation, domain=n_ent, range=l_string)
+        p_comment = p_annotation.get_child(ns.bse.comment, unique=True)
+        self.assertEqual(Schema({p_comment}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            xsd:string rdfs:subClassOf bsfs:Literal .
+
+            bsfs:Annotation rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range xsd:string .
+
+            bse:comment rdfs:subClassOf bsfs:Annotation ; # inherits domain/range from bsfs:Annotation
+                bsfs:unique "true"^^xsd:boolean .
+            '''))
+
+        # we can define partial predicates (w/o specifying a usable range)
+        n_ent = types.ROOT_NODE.get_child(ns.bsfs.Entity)
+        l_string = types.ROOT_LITERAL.get_child(ns.xsd.string)
+        p_annotation = types.ROOT_PREDICATE.get_child(ns.bsfs.Annotation, domain=n_ent)
+        p_comment = p_annotation.get_child(ns.bse.comment, range=l_string, unique=False)
+        self.assertEqual(Schema({p_comment}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            xsd:string rdfs:subClassOf bsfs:Literal .
+
+            bsfs:Annotation rdfs:subClassOf bsfs:Predicate ; # derive predicate w/o setting range
+                rdfs:domain bsfs:Entity .
+
+            bse:comment rdfs:subClassOf bsfs:Annotation ; # derived predicate w/ setting range
+                rdfs:range xsd:string ;
+                bsfs:unique "false"^^xsd:boolean .
+            '''))
+
+        # predicate definition can be split across multiple statements.
+        # statements can be repeated
+        n_ent = types.ROOT_NODE.get_child(ns.bsfs.Entity)
+        p_foo = types.ROOT_PREDICATE.get_child(ns.bse.foo, domain=n_ent, range=types.ROOT_NODE, unique=True)
+        self.assertEqual(Schema({p_foo}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:foo rdfs:subClassOf bsfs:Predicate ;
+                rdfs:range bsfs:Node ;
+                bsfs:unique "true"^^xsd:boolean .
+
+            bse:foo rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity.
+            '''))
+
+        # domain must be a subtype of parent's domain
+        n_ent = types.ROOT_NODE.get_child(ns.bsfs.Entity)
+        n_image = n_ent.get_child(ns.bsfs.Image)
+        p_foo = types.ROOT_PREDICATE.get_child(ns.bse.foo, domain=types.ROOT_NODE)
+        p_bar = p_foo.get_child(ns.bse.bar, domain=n_ent)
+        p_foobar = p_bar.get_child(ns.bse.foobar, domain=n_image)
+        self.assertEqual(Schema({p_foobar}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            bsfs:Image rdfs:subClassOf bsfs:Entity .
+
+            bse:foo rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Node .
+            bse:bar rdfs:subClassOf bse:foo ;
+                rdfs:domain bsfs:Entity .
+            bse:foobar rdfs:subClassOf bse:bar ;
+                rdfs:domain bsfs:Image .
+            '''))
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            bsfs:Image rdfs:subClassOf bsfs:Entity .
+
+            bse:foo rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Image .
+            bse:bar rdfs:subClassOf bse:foo ;
+                rdfs:domain bsfs:Entity .
+            bse:foobar rdfs:subClassOf bse:bar ;
+                rdfs:domain bsfs:Node .
+            ''')
+
+        # range must be a subtype of parent's range
+        n_ent = types.ROOT_NODE.get_child(ns.bsfs.Entity)
+        n_image = n_ent.get_child(ns.bsfs.Image)
+        p_foo = types.ROOT_PREDICATE.get_child(ns.bse.foo, range=types.ROOT_NODE)
+        p_bar = p_foo.get_child(ns.bse.bar, range=n_ent)
+        p_foobar = p_bar.get_child(ns.bse.foobar, range=n_image)
+        self.assertEqual(Schema({p_foobar}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            bsfs:Image rdfs:subClassOf bsfs:Entity .
+
+            bse:foo rdfs:subClassOf bsfs:Predicate ;
+                rdfs:range bsfs:Node .
+            bse:bar rdfs:subClassOf bse:foo ;
+                rdfs:range bsfs:Entity .
+            bse:foobar rdfs:subClassOf bse:bar ;
+                rdfs:range bsfs:Image .
+            '''))
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            bsfs:Image rdfs:subClassOf bsfs:Entity .
+
+            bse:foo rdfs:subClassOf bsfs:Predicate ;
+                rdfs:range bsfs:Image .
+            bse:bar rdfs:subClassOf bse:foo ;
+                rdfs:range bsfs:Entity .
+            bse:foobar rdfs:subClassOf bse:bar ;
+                rdfs:range bsfs:Node .
+            ''')
+
+        # cannot define the same predicate from multiple parents
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            bsfs:Annotation rdfs:subClassOf bsfs:Predicate .
+
+            bse:foo rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Node ;
+                rdfs:range bsfs:Node ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            bse:foo rdfs:subClassOf bsfs:Annotation ;
+                rdfs:domain bsfs:Node ;
+                rdfs:range bsfs:Node ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            ''')
+        # cannot assign multiple conflicting domains to the same predicate
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:foo rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Node ;
+                rdfs:range bsfs:Node ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            bse:foo rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity . # conflicting domain
+            ''')
+        # cannot assign multiple conflicting ranges to the same predicate
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:foo rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Node ;
+                rdfs:range bsfs:Node ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            bse:foo rdfs:subClassOf bsfs:Predicate ;
+                rdfs:range bsfs:Entity . # conflicting range
+            ''')
+        # cannot assign multiple conflicting uniques to the same predicate
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:foo rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Node ;
+                rdfs:range bsfs:Node ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            bse:foo rdfs:subClassOf bsfs:Predicate ;
+                bsfs:unique "true"^^xsd:boolean . # conflicting unique
+            ''')
+
+        # predicates can have annotations
+        self.assertDictEqual(from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bse:comment rdfs:subClassOf bsfs:Predicate ;
+                rdfs:range bsfs:Node .
+
+            ''').predicate(ns.bse.comment).annotations, {})
+        self.assertDictEqual(from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bse:comment rdfs:subClassOf bsfs:Predicate ;
+                rdfs:range bsfs:Node ;
+                rdfs:label "hello world"^^xsd:string ;
+                bsfs:foo "1234"^^xsd:integer .
+
+            ''').predicate(ns.bse.comment).annotations, {
+            ns.rdfs.label: 'hello world',
+            ns.bsfs.foo: 1234,
+            })
+
+
+    def test_feature(self):
+        # domain must be defined
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:array rdfs:subClassOf bsfs:Literal .
+
+            bse:colors rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Entity ; # undefined symbol
+                rdfs:range bsfs:array ;
+                bsfs:unique "false"^^xsd:boolean .
+            ''')
+        # domain cannot be a literal
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Entity rdfs:subClassOf bsfs:Literal .
+            bsfs:array rdfs:subClassOf bsfs:Literal .
+
+            bse:colors rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Entity ; # literal instead of node
+                rdfs:range bsfs:array ;
+                bsfs:unique "false"^^xsd:boolean .
+            ''')
+
+        # range must be defined
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:colors rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range bsfs:array ; # undefined symbol
+                bsfs:unique "false"^^xsd:boolean .
+            ''')
+        # range must be defined
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:colors rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range bsfs:Foo ; # undefined symbol
+                bsfs:unique "false"^^xsd:boolean .
+            ''')
+        # range must be a node or a literal
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:colors rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range bsfs:Predicate ; # invalid symbol
+                bsfs:unique "false"^^xsd:boolean .
+            ''')
+
+        # additional predicates can be defined
+        n_ent = types.ROOT_NODE.get_child(ns.bsfs.Entity)
+        l_array = types.ROOT_LITERAL.get_child(ns.bsfs.array)
+        p_comment = types.ROOT_FEATURE.get_child(ns.bse.colors, domain=n_ent, range=l_array, unique=False)
+        self.assertEqual(Schema({p_comment}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            bsfs:array rdfs:subClassOf bsfs:Literal .
+
+            bse:colors rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range bsfs:array ;
+                bsfs:unique "false"^^xsd:boolean .
+            '''))
+
+        # features inherit properties from parents
+        n_ent = types.ROOT_NODE.get_child(ns.bsfs.Entity)
+        l_array = types.ROOT_LITERAL.get_child(ns.bsfs.array)
+        l_string = types.ROOT_LITERAL.get_child(ns.xsd.string)
+        p_annotation = types.ROOT_FEATURE.get_child(ns.bsfs.Annotation, domain=n_ent, range=l_array,
+            dimension=1234, dtype=ns.xsd.string)
+        p_comment = p_annotation.get_child(ns.bse.colors, unique=True)
+        self.assertEqual(Schema({p_comment}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            bsfs:array rdfs:subClassOf bsfs:Literal .
+
+            bsfs:Annotation rdfs:subClassOf bsfs:Feature ; # inherits defaults from bsfs:Feature
+                rdfs:domain bsfs:Entity ;
+                rdfs:range bsfs:array ;
+                bsfs:dimension "1234"^^xsd:integer ;
+                bsfs:dtype xsd:string .
+
+            bse:colors rdfs:subClassOf bsfs:Annotation ; # inherits domain/range/etc. from bsfs:Annotation
+                bsfs:unique "true"^^xsd:boolean . # overwrites bsfs:Predicate
+            '''))
+
+        # feature definition can be split across multiple statements.
+        # statements can be repeated
+        n_ent = types.ROOT_NODE.get_child(ns.bsfs.Entity)
+        p_foo = types.ROOT_FEATURE.get_child(ns.bse.foo, domain=n_ent, unique=True,
+                dimension=1234, dtype=ns.bsfs.f32)
+        self.assertEqual(Schema({p_foo}), from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                bsfs:unique "true"^^xsd:boolean ;
+                bsfs:dimension "1234"^^xsd:integer .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Entity ;
+                bsfs:dtype bsfs:f32 .
+            '''))
+
+        # cannot define the same feature from multiple parents
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Annotation rdfs:subClassOf bsfs:Feature .
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Node ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            bse:foo rdfs:subClassOf bsfs:Annotation ;
+                rdfs:domain bsfs:Node ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            ''')
+        # cannot assign multiple conflicting domains to the same feature
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Node ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Entity . # conflicting domain
+            ''')
+        # cannot assign multiple conflicting ranges to the same feature
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            bsfs:array rdfs:subClassOf bsfs:Literal .
+            bsfs:large_array rdfs:subClassOf bsfs:array .
+            bsfs:small_array rdfs:subClassOf bsfs:array .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Node ;
+                rdfs:range bsfs:large_array ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                rdfs:range bsfs:small_array . # conflicting range
+            ''')
+        # cannot assign multiple conflicting uniques to the same feature
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Node ;
+                rdfs:range bsfs:Node ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                bsfs:unique "true"^^xsd:boolean . # conflicting unique
+            ''')
+        # cannot assign multiple conflicting dimensions to the same feature
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Node ;
+                bsfs:dimension "1234"^^xsd:integer .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                bsfs:dimension "4321"^^xsd:integer . # conflicting dimension
+            ''')
+        # cannot assign multiple conflicting dtypes to the same feature
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Node ;
+                bsfs:dtype bsfs:f32 .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                bsfs:dtype bsfs:f16 . # conflicting dtype
+            ''')
+        # cannot assign multiple conflicting distance metrics to the same feature
+        self.assertRaises(errors.ConsistencyError, from_string, '''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Node ;
+                bsfs:distance bsfs:euclidean .
+
+            bse:foo rdfs:subClassOf bsfs:Feature ;
+                bsfs:distance bsfs:cosine . # conflicting distance
+            ''')
+
+        # features can have annotations
+        self.assertDictEqual(from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bse:colors rdfs:subClassOf bsfs:Feature ;
+                bsfs:dimension "1234"^^xsd:integer .
+
+            ''').predicate(ns.bse.colors).annotations, {})
+        self.assertDictEqual(from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+            bse:colors rdfs:subClassOf bsfs:Feature ;
+                bsfs:dimension "1234"^^xsd:integer ;
+                rdfs:label "hello world"^^xsd:string ;
+                bsfs:foo "1234"^^xsd:integer .
+
+            ''').predicate(ns.bse.colors).annotations, {
+            ns.rdfs.label: 'hello world',
+            ns.bsfs.foo: 1234,
+            })
+
+
+    def test_integration(self):
+        # nodes
+        n_ent = types.ROOT_NODE.get_child(ns.bsfs.Entity)
+        n_tag = types.ROOT_NODE.get_child(ns.bsfs.Tag)
+        n_image = n_ent.get_child(ns.bsfs.Image)
+        # literals
+        l_string = types.ROOT_LITERAL.get_child(ns.xsd.string)
+        l_array = types.ROOT_LITERAL.get_child(ns.bsfs.array)
+        l_integer = types.ROOT_LITERAL.get_child(ns.xsd.integer)
+        l_boolean = types.ROOT_LITERAL.get_child(ns.xsd.boolean)
+        # predicates
+        p_annotation = types.ROOT_PREDICATE.get_child(ns.bsfs.Annotation)
+        p_tag = types.ROOT_PREDICATE.get_child(ns.bse.tag, domain=n_ent, range=n_tag)
+        p_group = p_tag.get_child(ns.bse.group, domain=n_image, unique=True)
+        p_comment = p_annotation.get_child(ns.bse.comment, range=l_string)
+        # features
+        f_colors = types.ROOT_FEATURE.get_child(URI('http://bsfs.ai/schema/Feature/colors_spatial'),
+            domain=n_ent, range=l_array, unique=True, dtype=ns.bsfs.f16, distance=ns.bsfs.euclidean)
+        f_colors1234 = f_colors.get_child(URI('http://bsfs.ai/schema/Feature/colors_spatial#1234'), dimension=1024)
+        f_colors4321 = f_colors.get_child(URI('http://bsfs.ai/schema/Feature/colors_spatial#4321'), dimension=2048)
+        # schema
+        ref = Schema(
+            {p_annotation, p_tag, p_group, p_comment, f_colors, f_colors1234, f_colors4321},
+            {n_ent, n_tag, n_image},
+            {l_string, l_integer, l_boolean})
+        # load from string
+        gen = from_string('''
+            # generic prefixes
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+
+            # bsfs prefixes
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+
+            # nodes
+            bsfs:Entity rdfs:subClassOf bsfs:Node ;
+                rdfs:label "Principal node"^^xsd:string .
+            bsfs:Tag rdfs:subClassOf bsfs:Node ;
+                rdfs:label "Tag"^^xsd:string .
+            bsfs:Image rdfs:subClassOf bsfs:Entity .
+
+            # literals
+            xsd:string rdfs:subClassOf bsfs:Literal ;
+                rdfs:label "A sequence of characters"^^xsd:string .
+            bsfs:array rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsfs:Literal .
+            xsd:boolean rdfs:subClassOf bsfs:Literal .
+
+            # abstract predicates
+            bsfs:Annotation rdfs:subClassOf bsfs:Predicate ;
+                rdfs:label "node annotation"^^xsd:string .
+            bsfs:Feature rdfs:subClassOf bsfs:Predicate .
+
+            # feature instances
+            <http://bsfs.ai/schema/Feature/colors_spatial> rdfs:subClassOf bsfs:Feature ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range bsfs:array ;
+                bsfs:unique "true"^^xsd:boolean ;
+                bsfs:dtype bsfs:f16 ;
+                bsfs:distance bsfs:euclidean ;
+                # annotations
+                rdfs:label "ColorsSpatial instances. Dimension depends on instance."^^xsd:string ;
+                bsfs:first_arg "1234"^^xsd:integer ;
+                bsfs:second_arg "hello world"^^xsd:string .
+
+            <http://bsfs.ai/schema/Feature/colors_spatial#1234> rdfs:subClassOf <http://bsfs.ai/schema/Feature/colors_spatial> ;
+                bsfs:dimension "1024"^^xsd:integer ;
+                rdfs:label "Main colors spatial instance"^^xsd:string .
+
+            <http://bsfs.ai/schema/Feature/colors_spatial#4321> rdfs:subClassOf <http://bsfs.ai/schema/Feature/colors_spatial> ;
+                bsfs:dimension "2048"^^xsd:integer .
+
+            # predicate instances
+            bse:tag rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range bsfs:Tag ;
+                bsfs:unique "false"^^xsd:boolean ;
+                # annotations
+                rdfs:label "connect entity to a tag"^^xsd:string .
+
+            bse:group rdfs:subClassOf bse:tag ; # subtype of another predicate
+                rdfs:domain bsfs:Image ;
+                bsfs:unique "true"^^xsd:boolean .
+
+            bse:comment rdfs:subClassOf bsfs:Annotation ; # subtype of abstract predicate
+                rdfs:domain bsfs:Node ;
+                rdfs:range xsd:string ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            ''')
+        # schemas are equal
+        self.assertEqual(ref, gen)
+        # check annotations
+        self.assertDictEqual(gen.node(ns.bsfs.Entity).annotations, {ns.rdfs.label: 'Principal node'})
+        self.assertDictEqual(gen.node(ns.bsfs.Tag).annotations, {ns.rdfs.label: 'Tag'})
+        self.assertDictEqual(gen.literal(ns.xsd.string).annotations, {ns.rdfs.label: 'A sequence of characters'})
+        self.assertDictEqual(gen.predicate(ns.bsfs.Annotation).annotations, {ns.rdfs.label: 'node annotation'})
+        self.assertDictEqual(gen.predicate(URI('http://bsfs.ai/schema/Feature/colors_spatial')).annotations, {
+            ns.rdfs.label: 'ColorsSpatial instances. Dimension depends on instance.',
+            ns.bsfs.first_arg: 1234,
+            ns.bsfs.second_arg: 'hello world',
+            })
+        self.assertDictEqual(gen.predicate(URI('http://bsfs.ai/schema/Feature/colors_spatial#1234')).annotations, {
+            ns.rdfs.label: 'Main colors spatial instance'})
+        self.assertDictEqual(gen.predicate(ns.bse.tag).annotations, {ns.rdfs.label: 'connect entity to a tag'})
+
+
+
+class TestToString(unittest.TestCase):
+    def test_stub(self):
+        raise NotImplementedError()
+
+
+## main ##
+
+if __name__ == '__main__':
+    unittest.main()
+
+## EOF ##