1 files changed, 29 insertions, 12 deletions
diff --git a/bsfs/triple_store/base.py b/bsfs/triple_store/base.py
index 6561262..58b5670 100644
--- a/bsfs/triple_store/base.py
+++ b/bsfs/triple_store/base.py
@@ -1,16 +1,12 @@
-"""
 
-Part of the BlackStar filesystem (bsfs) module.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
 import abc
 import typing
 
 # inner-module imports
+from bsfs.query import ast
 from bsfs.utils import URI, typename
-import bsfs.schema  as _schema
+import bsfs.schema  as bsc
 
 # exports
 __all__: typing.Sequence[str] = (
@@ -81,12 +77,12 @@ class TripleStoreBase(abc.ABC):
 
     @property
     @abc.abstractmethod
-    def schema(self) -> _schema.Schema:
+    def schema(self) -> bsc.Schema:
         """Return the store's local schema."""
 
     @schema.setter
     @abc.abstractmethod
-    def schema(self, schema: _schema.Schema):
+    def schema(self, schema: bsc.Schema):
         """Migrate to new schema by adding or removing class definitions.
 
         Commits before and after the migration.
@@ -109,9 +105,30 @@ class TripleStoreBase(abc.ABC):
         """
 
     @abc.abstractmethod
+    def get(
+            self,
+            node_type: bsc.Node,
+            filter: typing.Optional[ast.filter.FilterExpression] = None, # pylint: disable=redefined-builtin
+            ) -> typing.Iterator[URI]:
+        """Return guids of nodes of type *node_type* that match the *filter*.
+        Return all guids of the respective type if *filter* is None.
+        """
+
+    @abc.abstractmethod
+    def fetch(
+            self,
+            node_type: bsc.Node,
+            filter: ast.filter.FilterExpression, # pylint: disable=redefined-builtin
+            fetch: ast.fetch.FetchExpression,
+            ) -> typing.Iterator[typing.Tuple[URI, str, typing.Any]]:
+        """Return (guid, name, value) triples where the guid is determined by the *filter*
+        query and the name matches the *fetch* query.
+        """
+
+    @abc.abstractmethod
     def exists(
             self,
-            node_type: _schema.Node,
+            node_type: bsc.Node,
             guids: typing.Iterable[URI],
             ) -> typing.Iterable[URI]:
         """Return those *guids* that exist and have type *node_type* or a subclass thereof."""
@@ -119,7 +136,7 @@ class TripleStoreBase(abc.ABC):
     @abc.abstractmethod
     def create(
             self,
-            node_type: _schema.Node,
+            node_type: bsc.Node,
             guids: typing.Iterable[URI],
             ):
         """Create *guid* nodes with type *subject*."""
@@ -127,9 +144,9 @@ class TripleStoreBase(abc.ABC):
     @abc.abstractmethod
     def set(
             self,
-            node_type: _schema.Node, # FIXME: is the node_type even needed? Couldn't I infer from the predicate?
+            node_type: bsc.Node, # FIXME: is the node_type even needed? Couldn't I infer from the predicate?
             guids: typing.Iterable[URI],
-            predicate: _schema.Predicate,
+            predicate: bsc.Predicate,
             values: typing.Iterable[typing.Any],
             ):
         """Add triples to the graph.