1 files changed, 36 insertions, 25 deletions

diff --git a/bsie/lib/bsie.py b/bsie/lib/bsie.py
index 3aeee2b..e087fa9 100644
--- a/bsie/lib/bsie.py
+++ b/bsie/lib/bsie.py
@@ -8,8 +8,6 @@ Author: Matthias Baumgartner, 2022
 import typing
 
 # bsie imports
-from bsie.tools.pipeline import Pipeline
-from bsie.utils.bsfs import URI, schema as schema_
 from bsie.tools import Pipeline
 from bsie.utils import bsfs, node, ns
 
@@ -30,11 +28,14 @@ class BSIE():
 
     """
 
+    # pipeline
+    _pipeline: Pipeline
+
     # predicates to extract.
-    predicates: typing.Set[URI]
+    _principals: typing.Set[bsfs.URI]
 
     # local schema.
-    schema: schema_.Schema
+    _schema: bsfs.schema.Schema
 
     def __init__(
             self,
@@ -46,36 +47,46 @@ class BSIE():
             discard: typing.Optional[typing.Iterable[bsfs.URI]] = None,
             ):
         # store pipeline
-        self.pipeline = pipeline
-        # start off with available predicates
-        self.predicates = {pred.uri for pred in self.pipeline.predicates()}
-        # limit predicates to specified ones by argument.
+        self._pipeline = pipeline
+        # start off with available principals
+        self._principals = {pred.uri for pred in self._pipeline.principals}
+        # limit principals to specified ones by argument.
         if collect is not None:
             collect = set(collect)
             if len(collect) > 0:
-                self.predicates &= collect
-        # discard predicates.
+                self._principals &= collect
+        # discard principals.
         if discard is not None:
-            self.predicates -= set(discard)
+            self._principals -= set(discard)
         # discard ns.bsfs.Predicate
-        self.predicates.discard(ns.bsfs.Predicate)
-        # compile a schema that only contains the requested predicates (and implied types)
-        self.schema = schema_.Schema({
-            self.pipeline.schema.predicate(pred) for pred in self.predicates})
+        self._principals.discard(ns.bsfs.Predicate)
+        # compile a schema that only contains the requested principals (and auxiliary predicates)
+        self._schema = self._pipeline.subschema(
+            self._pipeline.schema.predicate(pred) for pred in self._principals)
+
+    @property
+    def schema(self) -> bsfs.schema.Schema:
+        """Return the BSIE schema."""
+        return self._schema
+
+    @property
+    def principals(self) -> typing.Iterator[bsfs.URI]:
+        """Return an iterator to the principal predicates."""
+        return iter(self._principals)
 
     def from_file(
             self,
-            path: URI,
-            predicates: typing.Optional[typing.Iterable[URI]] = None,
-            ) -> typing.Iterator[typing.Tuple[node.Node, URI, typing.Any]]:
-        """Produce triples for a given *path*. Limit to *predicates* if given."""
-        # get requested predicates.
-        predicates = set(predicates) if predicates is not None else self.predicates
-        # filter through requested predicates.
-        predicates &= self.predicates
+            path: bsfs.URI,
+            principals: typing.Optional[typing.Iterable[bsfs.URI]] = None,
+            ) -> typing.Iterator[typing.Tuple[node.Node, bsfs.URI, typing.Any]]:
+        """Produce triples for a given *path*. Limit to *principals* if given."""
+        # get requested principals.
+        principals = set(principals) if principals is not None else self._principals
+        # filter through requested principals.
+        principals &= self._principals
         # predicate lookup
-        predicates = {self.schema.predicate(pred) for pred in predicates}
+        principals = {self.schema.predicate(pred) for pred in principals}
         # invoke pipeline
-        yield from self.pipeline(path, predicates)
+        yield from self._pipeline(path, principals)
 
 ## EOF ##