extractor interface revision

* schema as property
* predicates -> principals

4 files changed, 22 insertions, 21 deletions

diff --git a/bsie/base/extractor.py b/bsie/base/extractor.py
index 678dcec..c44021b 100644
--- a/bsie/base/extractor.py
+++ b/bsie/base/extractor.py
@@ -9,8 +9,6 @@ import abc
 import typing
 
 # bsie imports
-from bsie.utils import node
-from bsie.utils.bsfs import schema as _schema, typename
 from bsie.utils import bsfs, node, ns
 
 # exports
@@ -58,10 +56,10 @@ class Extractor(abc.ABC):
     CONTENT_READER: typing.Optional[str] = None
 
     # extractor schema.
-    schema: _schema.Schema
+    _schema: bsfs.schema.Schema
 
-    def __init__(self, schema: _schema.Schema):
-        self.schema = schema
+    def __init__(self, schema: bsfs.schema.Schema):
+        self._schema = schema
 
     def __str__(self) -> str:
         return bsfs.typename(self)
@@ -77,7 +75,14 @@ class Extractor(abc.ABC):
     def __hash__(self) -> int:
         return hash((type(self), self.CONTENT_READER, self.schema))
 
-    def predicates(self) -> typing.Iterator[_schema.Predicate]:
+    @property
+    def schema(self) -> bsfs.schema.Schema:
+        """Return the extractor's schema."""
+        return self._schema
+
+    @property
+    def principals(self) -> typing.Iterator[bsfs.schema.Predicate]:
+        """Return the principal predicates, i.e., relations from/to the extraction subject."""
         ent = self.schema.node(ns.bsfs.Entity)
         return (
             pred
@@ -91,8 +96,8 @@ class Extractor(abc.ABC):
             self,
             subject: node.Node,
             content: typing.Any,
-            predicates: typing.Iterable[_schema.Predicate],
-            ) -> typing.Iterator[typing.Tuple[node.Node, _schema.Predicate, typing.Any]]:
+            principals: typing.Iterable[bsfs.schema.Predicate],
+            ) -> typing.Iterator[typing.Tuple[node.Node, bsfs.schema.Predicate, typing.Any]]:
         """Return (node, predicate, value) triples."""
 
 ## EOF ##
diff --git a/bsie/extractor/generic/constant.py b/bsie/extractor/generic/constant.py
index f9e3415..cdb2ef6 100644
--- a/bsie/extractor/generic/constant.py
+++ b/bsie/extractor/generic/constant.py
@@ -9,8 +9,6 @@ import typing
 
 # bsie imports
 from bsie.base import extractor
-from bsie.utils.bsfs import URI, schema as _schema
-from bsie.utils.node import Node
 from bsie.utils import bsfs, node
 
 # exports
@@ -50,10 +48,10 @@ class Constant(extractor.Extractor):
             self,
             subject: node.Node,
             content: None,
-            predicates: typing.Iterable[_schema.Predicate],
-            ) -> typing.Iterator[typing.Tuple[Node, _schema.Predicate, typing.Any]]:
+            principals: typing.Iterable[bsfs.schema.Predicate],
+            ) -> typing.Iterator[typing.Tuple[node.Node, bsfs.schema.Predicate, typing.Any]]:
         for pred, value in self._tuples:
-            if pred in predicates:
+            if pred in principals:
                 yield subject, pred, value
 
 ## EOF ##
diff --git a/bsie/extractor/generic/path.py b/bsie/extractor/generic/path.py
index 00165e3..23ae80b 100644
--- a/bsie/extractor/generic/path.py
+++ b/bsie/extractor/generic/path.py
@@ -10,7 +10,6 @@ import typing
 
 # bsie imports
 from bsie.base import extractor
-from bsie.utils.bsfs import schema
 from bsie.utils import bsfs, node, ns
 
 # exports
@@ -46,9 +45,9 @@ class Path(extractor.Extractor):
             self,
             subject: node.Node,
             content: str,
-            predicates: typing.Iterable[schema.Predicate],
-            ) -> typing.Iterator[typing.Tuple[node.Node, schema.Predicate, typing.Any]]:
-        for pred in predicates:
+            principals: typing.Iterable[bsfs.schema.Predicate],
+            ) -> typing.Iterator[typing.Tuple[node.Node, bsfs.schema.Predicate, typing.Any]]:
+        for pred in principals:
             # find callback
             clbk = self._callmap.get(pred)
             if clbk is None:
diff --git a/bsie/extractor/generic/stat.py b/bsie/extractor/generic/stat.py
index 0f4267f..1dcfedf 100644
--- a/bsie/extractor/generic/stat.py
+++ b/bsie/extractor/generic/stat.py
@@ -10,7 +10,6 @@ import typing
 
 # bsie imports
 from bsie.base import extractor
-from bsie.utils.bsfs import schema as _schema
 from bsie.utils import bsfs, node, ns
 
 # exports
@@ -46,9 +45,9 @@ class Stat(extractor.Extractor):
             self,
             subject: node.Node,
             content: os.stat_result,
-            predicates: typing.Iterable[_schema.Predicate],
-            ) -> typing.Iterator[typing.Tuple[node.Node, _schema.Predicate, typing.Any]]:
-        for pred in predicates:
+            principals: typing.Iterable[bsfs.schema.Predicate],
+            ) -> typing.Iterator[typing.Tuple[node.Node, bsfs.schema.Predicate, typing.Any]]:
+        for pred in principals:
             # find callback
             clbk = self._callmap.get(pred)
             if clbk is None: