graph schema migration

3 files changed, 140 insertions, 0 deletions

diff --git a/bsfs/graph/graph.py b/bsfs/graph/graph.py
index 71973c2..4a36ff6 100644
--- a/bsfs/graph/graph.py
+++ b/bsfs/graph/graph.py
@@ -5,6 +5,7 @@ A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
 # imports
+import os
 import typing
 
 # bsfs imports
@@ -35,6 +36,8 @@ class Graph():
     def __init__(self, backend: TripleStoreBase, user: URI):
         self._backend = backend
         self._user = user
+        # ensure Graph schema requirements
+        self.migrate(self._backend.schema)
 
     def __hash__(self) -> int:
         return hash((type(self), self._backend, self._user))
@@ -55,7 +58,28 @@ class Graph():
         """Return the store's local schema."""
         return self._backend.schema
 
+    def migrate(self, schema: Schema, append: bool = True) -> 'Graph':
+        """Migrate the current schema to a new *schema*.
+
+        Appends to the current schema by default; control this via *append*.
+        The `Graph` may add additional classes to the schema that are required for its interals.
+
         """
+        # check args
+        if not isinstance(schema, Schema):
+            raise TypeError(schema)
+        # append to current schema
+        if append:
+            schema = schema + self._backend.schema
+        # add Graph schema requirements
+        with open(os.path.join(os.path.dirname(__file__), 'schema.nt'), mode='rt', encoding='UTF-8') as ifile:
+            schema = schema + Schema.from_string(ifile.read())
+        # migrate schema in backend
+        # FIXME: consult access controls!
+        self._backend.schema = schema
+        # return self
+        return self
+
     def nodes(self, node_type: URI, guids: typing.Iterable[URI]) -> _nodes.Nodes:
         """
         node_type = self.schema.node(node_type)
diff --git a/bsfs/graph/schema.nt b/bsfs/graph/schema.nt
new file mode 100644
index 0000000..8612681
--- /dev/null
+++ b/bsfs/graph/schema.nt
@@ -0,0 +1,18 @@
+
+# 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 bsm: <http://bsfs.ai/schema/Meta#>
+
+# literals
+xsd:integer rdfs:subClassOf bsfs:Literal .
+
+# predicates
+bsm:t_created rdfs:subClassOf bsfs:Predicate ;
+    rdfs:domain bsfs:Node ;
+    rdfs:range xsd:integer ;
+    bsfs:unique "true"^^xsd:boolean .
+
diff --git a/test/graph/test_graph.py b/test/graph/test_graph.py
index eaeee0c..0b16527 100644
--- a/test/graph/test_graph.py
+++ b/test/graph/test_graph.py
@@ -84,6 +84,104 @@ class TestGraph(unittest.TestCase):
         # node_type must be in the schema
         self.assertRaises(KeyError, graph.nodes, ns.bsfs.Invalid, guids)
 
+    def test_migrate(self):
+        # setup
+        graph = Graph(self.backend, self.user)
+
+        # argument must be a schema
+        class Foo(): pass
+        self.assertRaises(TypeError, graph.migrate, 'hello world')
+        self.assertRaises(TypeError, graph.migrate, 1234)
+        self.assertRaises(TypeError, graph.migrate, Foo())
+
+        # cannot append inconsistent schema
+        self.assertRaises(errors.ConsistencyError, graph.migrate, schema.Schema({}, {
+            schema.Node(ns.bsfs.Entity,
+                schema.Node(ns.bsfs.Intermediate,
+                    schema.Node(ns.bsfs.Node, None)))}), append=True)
+
+        # cannot migrate to inconsistent schema
+        self.assertRaises(errors.ConsistencyError, graph.migrate, schema.Schema({}, {
+            schema.Node(ns.bsfs.Entity,
+                schema.Node(ns.bsfs.Intermediate,
+                    schema.Node(ns.bsfs.Node, None)))}), append=False)
+
+        # can migrate to compatible schema
+        target_1 = schema.Schema.from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            xsd:string rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsfs:Literal .
+
+            bse:filename 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 .
+
+            ''')
+        graph.migrate(target_1)
+        # new schema is applied
+        self.assertLess(target_1, graph.schema)
+        # graph appends its predicates
+        self.assertEqual(graph.schema, target_1 + schema.Schema.from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bsm: <http://bsfs.ai/schema/Meta#>
+            xsd:integer rdfs:subClassOf bsfs:Literal .
+            bsm:t_created rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Node ;
+                rdfs:range xsd:integer ;
+                bsfs:unique "true"^^xsd:boolean .
+            '''))
+
+        # can overwrite the current schema
+        target_2 = schema.Schema.from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bse: <http://bsfs.ai/schema/Entity#>
+            bsfs:Entity rdfs:subClassOf bsfs:Node .
+            xsd:string rdfs:subClassOf bsfs:Literal .
+            xsd:integer rdfs:subClassOf bsfs:Literal .
+
+            bse:filename rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range xsd:string ;
+                bsfs:unique "false"^^xsd:boolean .
+
+            bse:author rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range xsd:string ;
+                bsfs:unique "true"^^xsd:boolean .
+
+            ''')
+        graph.migrate(target_2, append=False)
+        # append overwrites existing predicates
+        self.assertFalse(target_1 <= graph.schema)
+        # new schema is applied
+        self.assertLess(target_2, graph.schema)
+        # graph appends its predicates
+        self.assertEqual(graph.schema, target_2 + schema.Schema.from_string('''
+            prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+            prefix xsd: <http://www.w3.org/2001/XMLSchema#>
+            prefix bsfs: <http://bsfs.ai/schema/>
+            prefix bsm: <http://bsfs.ai/schema/Meta#>
+            xsd:integer rdfs:subClassOf bsfs:Literal .
+            bsm:t_created rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Node ;
+                rdfs:range xsd:integer ;
+                bsfs:unique "true"^^xsd:boolean .
+            '''))
+
 
 ## main ##