package restructuring: base

* Reader and Extractor to respective reader/extractor modules
* ReaderBuilder to reader module
* ExtractorBuilder to extractor module
* Loading module in utils (safe_load, unpack_name)
* Pipeline and PipelineBuilder to lib module
* errors to utils
* documentation: "standard import" and "external import"

41 files changed, 727 insertions, 606 deletions

diff --git a/bsie/apps/index.py b/bsie/apps/index.py
index 1dbfdd8..0c6296f 100644
--- a/bsie/apps/index.py
+++ b/bsie/apps/index.py
@@ -4,16 +4,16 @@ Part of the bsie module.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import argparse
 import os
 import typing
 
 # bsie imports
-from bsie.base import errors
-from bsie.lib import BSIE
-from bsie.tools import builder
-from bsie.utils import bsfs
+from bsie.extractor import ExtractorBuilder
+from bsie.lib import BSIE, PipelineBuilder
+from bsie.reader import ReaderBuilder
+from bsie.utils import bsfs, errors
 
 # exports
 __all__: typing.Sequence[str] = (
@@ -44,9 +44,9 @@ def main(argv):
 
     # FIXME: Read reader/extractor configs from a config file
     # reader builder
-    rbuild = builder.ReaderBuilder({})
+    rbuild = ReaderBuilder({})
     # extractor builder
-    ebuild = builder.ExtractorBuilder([
+    ebuild = ExtractorBuilder([
         {'bsie.extractor.generic.path.Path': {}},
         {'bsie.extractor.generic.stat.Stat': {}},
         {'bsie.extractor.generic.constant.Constant': dict(
@@ -60,7 +60,7 @@ def main(argv):
             )},
         ])
     # pipeline builder
-    pbuild = builder.PipelineBuilder(
+    pbuild = PipelineBuilder(
         bsfs.Namespace(args.user + ('/' if not args.user.endswith('/') else '')),
         rbuild,
         ebuild,
diff --git a/bsie/apps/info.py b/bsie/apps/info.py
index eaf1f71..a4e611c 100644
--- a/bsie/apps/info.py
+++ b/bsie/apps/info.py
@@ -4,15 +4,16 @@ Part of the bsie module.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import argparse
 import sys
 import typing
 
 # bsie imports
-from bsie.base import errors
-from bsie.tools import builder
-from bsie.utils import bsfs
+from bsie.extractor import ExtractorBuilder
+from bsie.lib import PipelineBuilder
+from bsie.reader import ReaderBuilder
+from bsie.utils import bsfs, errors
 
 # exports
 __all__: typing.Sequence[str] = (
@@ -31,9 +32,10 @@ def main(argv):
 
     # FIXME: Read reader/extractor configs from a config file
     # reader builder
-    rbuild = builder.ReaderBuilder({})
+    rbuild = ReaderBuilder({
+        })
     # extractor builder
-    ebuild = builder.ExtractorBuilder([
+    ebuild = ExtractorBuilder([
         {'bsie.extractor.generic.path.Path': {}},
         {'bsie.extractor.generic.stat.Stat': {}},
         {'bsie.extractor.generic.constant.Constant': dict(
@@ -47,7 +49,7 @@ def main(argv):
             )},
         ])
     # pipeline builder
-    pbuild = builder.PipelineBuilder(
+    pbuild = PipelineBuilder(
         bsfs.Namespace('http://example.com/me/'), # not actually used
         rbuild,
         ebuild,
diff --git a/bsie/base/__init__.py b/bsie/base/__init__.py
deleted file mode 100644
index 0d362cd..0000000
--- a/bsie/base/__init__.py
+++ /dev/null
@@ -1,24 +0,0 @@
-"""The base module defines the BSIE interfaces.
-
-You'll mostly find abstract classes here.
-
-Part of the bsie module.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
-# imports
-import typing
-
-# inner-module imports
-from . import errors
-from .extractor import Extractor
-from .reader import Reader
-
-# exports
-__all__: typing.Sequence[str] = (
-    'Extractor',
-    'Reader',
-    'errors',
-    )
-
-## EOF ##
diff --git a/bsie/extractor/__init__.py b/bsie/extractor/__init__.py
index ef31343..5f385ee 100644
--- a/bsie/extractor/__init__.py
+++ b/bsie/extractor/__init__.py
@@ -6,10 +6,17 @@ Part of the bsie module.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import typing
 
+# inner-module imports
+from .base import Extractor
+from .builder import ExtractorBuilder
+
 # exports
-__all__: typing.Sequence[str] = []
+__all__: typing.Sequence[str] = (
+    'Extractor',
+    'ExtractorBuilder',
+    )
 
 ## EOF ##
diff --git a/bsie/base/extractor.py b/bsie/extractor/base.py
index c44021b..c44021b 100644
--- a/bsie/base/extractor.py
+++ b/bsie/extractor/base.py
diff --git a/bsie/extractor/builder.py b/bsie/extractor/builder.py
new file mode 100644
index 0000000..0fd3685
--- /dev/null
+++ b/bsie/extractor/builder.py
@@ -0,0 +1,77 @@
+"""
+
+Part of the bsie module.
+A copy of the license is provided with the project.
+Author: Matthias Baumgartner, 2022
+"""
+# standard imports
+import typing
+
+# bsie imports
+from bsie.utils import bsfs, errors, safe_load, unpack_qualified_name
+
+# inner-module imports
+from . import base
+
+# exports
+__all__: typing.Sequence[str] = (
+    'ExtractorBuilder',
+    )
+
+
+## code ##
+
+class ExtractorBuilder():
+    """Build `bsie.base.Extractor instances.
+
+    It is permissible to build multiple instances of the same extractor
+    (typically with different arguments), hence the ExtractorBuilder
+    receives a list of build specifications. Each specification is
+    a dict with a single key (extractor's qualified name) and a dict
+    to be used as keyword arguments.
+    Example: [{'bsie.extractor.generic.path.Path': {}}, ]
+
+    """
+
+    # build specifications
+    _specs: typing.List[typing.Dict[str, typing.Dict[str, typing.Any]]]
+
+    def __init__(self, specs: typing.List[typing.Dict[str, typing.Dict[str, typing.Any]]]):
+        self._specs = specs
+
+    def __iter__(self) -> typing.Iterator[int]:
+        """Iterate over extractor specifications."""
+        return iter(range(len(self._specs)))
+
+    def build(self, index: int) -> base.Extractor:
+        """Return an instance of the n'th extractor (n=*index*)."""
+        # get build instructions
+        specs = self._specs[index]
+
+        # check specs structure. expecting[{name: {kwargs}}]
+        if not isinstance(specs, dict):
+            raise TypeError(f'expected a dict, found {bsfs.typename(specs)}')
+        if len(specs) != 1:
+            raise TypeError(f'expected a dict of length one, found {len(specs)}')
+
+        # get name and args from specs
+        name = next(iter(specs.keys()))
+        kwargs = specs[name]
+
+        # check kwargs structure
+        if not isinstance(kwargs, dict):
+            raise TypeError(f'expected a dict, found {bsfs.typename(kwargs)}')
+
+        # check name and get module/class components
+        module_name, class_name = unpack_qualified_name(name)
+
+        # import extractor class
+        cls = safe_load(module_name, class_name)
+
+        try: # build and return instance
+            return cls(**kwargs)
+
+        except Exception as err:
+            raise errors.BuilderError(f'failed to build extractor {name} due to {bsfs.typename(err)}: {err}') from err
+
+## EOF ##
diff --git a/bsie/extractor/generic/constant.py b/bsie/extractor/generic/constant.py
index 11384e6..7b1d942 100644
--- a/bsie/extractor/generic/constant.py
+++ b/bsie/extractor/generic/constant.py
@@ -4,13 +4,15 @@ Part of the bsie module.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import typing
 
 # bsie imports
-from bsie.base import extractor
 from bsie.utils import bsfs, node
 
+# inner-module imports
+from .. import base
+
 # exports
 __all__: typing.Sequence[str] = (
     'Constant',
@@ -19,7 +21,7 @@ __all__: typing.Sequence[str] = (
 
 ## code ##
 
-class Constant(extractor.Extractor):
+class Constant(base.Extractor):
     """Extract information from file's path."""
 
     CONTENT_READER = None
@@ -32,7 +34,7 @@ class Constant(extractor.Extractor):
             schema: str,
             tuples: typing.Iterable[typing.Tuple[bsfs.URI, typing.Any]],
             ):
-        super().__init__(bsfs.schema.Schema.from_string(extractor.SCHEMA_PREAMBLE + schema))
+        super().__init__(bsfs.schema.Schema.from_string(base.SCHEMA_PREAMBLE + schema))
         # NOTE: Raises a KeyError if the predicate is not part of the schema
         self._tuples = tuple((self.schema.predicate(p_uri), value) for p_uri, value in tuples)
         # TODO: use schema instance for value checking
diff --git a/bsie/extractor/generic/path.py b/bsie/extractor/generic/path.py
index 7018e12..295715f 100644
--- a/bsie/extractor/generic/path.py
+++ b/bsie/extractor/generic/path.py
@@ -4,12 +4,12 @@ Part of the bsie module.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import os
 import typing
 
 # bsie imports
-from bsie.base import extractor
+from bsie.extractor import base
 from bsie.utils import bsfs, node, ns
 
 # exports
@@ -20,7 +20,7 @@ __all__: typing.Sequence[str] = (
 
 ## code ##
 
-class Path(extractor.Extractor):
+class Path(base.Extractor):
     """Extract information from file's path."""
 
     CONTENT_READER = 'bsie.reader.path.Path'
@@ -29,7 +29,7 @@ class Path(extractor.Extractor):
     _callmap: typing.Dict[bsfs.schema.Predicate, typing.Callable[[str], typing.Any]]
 
     def __init__(self):
-        super().__init__(bsfs.schema.Schema.from_string(extractor.SCHEMA_PREAMBLE + '''
+        super().__init__(bsfs.schema.Schema.from_string(base.SCHEMA_PREAMBLE + '''
             bse:filename rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:File ;
                 rdfs:range xsd:string ;
diff --git a/bsie/extractor/generic/stat.py b/bsie/extractor/generic/stat.py
index 0b9ce29..1381fe2 100644
--- a/bsie/extractor/generic/stat.py
+++ b/bsie/extractor/generic/stat.py
@@ -4,14 +4,16 @@ Part of the bsie module.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import os
 import typing
 
 # bsie imports
-from bsie.base import extractor
 from bsie.utils import bsfs, node, ns
 
+# inner-module imports
+from .. import base
+
 # exports
 __all__: typing.Sequence[str] = (
     'Stat',
@@ -20,7 +22,7 @@ __all__: typing.Sequence[str] = (
 
 ## code ##
 
-class Stat(extractor.Extractor):
+class Stat(base.Extractor):
     """Extract information from the file system."""
 
     CONTENT_READER = 'bsie.reader.stat.Stat'
@@ -29,7 +31,7 @@ class Stat(extractor.Extractor):
     _callmap: typing.Dict[bsfs.schema.Predicate, typing.Callable[[os.stat_result], typing.Any]]
 
     def __init__(self):
-        super().__init__(bsfs.schema.Schema.from_string(extractor.SCHEMA_PREAMBLE + '''
+        super().__init__(bsfs.schema.Schema.from_string(base.SCHEMA_PREAMBLE + '''
             bse:filesize rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:File ;
                 rdfs:range xsd:integer ;
diff --git a/bsie/lib/__init__.py b/bsie/lib/__init__.py
index 578c2c4..4239d3b 100644
--- a/bsie/lib/__init__.py
+++ b/bsie/lib/__init__.py
@@ -4,15 +4,17 @@ Part of the bsie module.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import typing
 
 # inner-module imports
 from .bsie import BSIE
+from .builder import PipelineBuilder
 
 # exports
 __all__: typing.Sequence[str] = (
     'BSIE',
+    'PipelineBuilder',
     )
 
 ## EOF ##
diff --git a/bsie/lib/bsie.py b/bsie/lib/bsie.py
index e087fa9..668783d 100644
--- a/bsie/lib/bsie.py
+++ b/bsie/lib/bsie.py
@@ -4,13 +4,15 @@ Part of the bsie module.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import typing
 
 # bsie imports
-from bsie.tools import Pipeline
 from bsie.utils import bsfs, node, ns
 
+# inner-module imports
+from .pipeline import Pipeline
+
 # exports
 __all__: typing.Sequence[str] = (
     'BSIE',
diff --git a/bsie/lib/builder.py b/bsie/lib/builder.py
new file mode 100644
index 0000000..c2abffe
--- /dev/null
+++ b/bsie/lib/builder.py
@@ -0,0 +1,85 @@
+"""
+
+Part of the bsie module.
+A copy of the license is provided with the project.
+Author: Matthias Baumgartner, 2022
+"""
+# standard imports
+import logging
+import typing
+
+# bsie imports
+from bsie.extractor import ExtractorBuilder
+from bsie.reader import ReaderBuilder
+from bsie.utils import bsfs, errors
+
+# inner-module imports
+from . import pipeline
+
+# exports
+__all__: typing.Sequence[str] = (
+    'PipelineBuilder',
+    )
+
+
+## code ##
+
+logger = logging.getLogger(__name__)
+
+class PipelineBuilder():
+    """Build `bsie.tools.pipeline.Pipeline` instances."""
+
+    # Prefix to be used in the Pipeline.
+    prefix: bsfs.Namespace
+
+    # builder for Readers.
+    rbuild: ReaderBuilder
+
+    # builder for Extractors.
+    ebuild: ExtractorBuilder
+
+    def __init__(
+            self,
+            prefix: bsfs.Namespace,
+            reader_builder: ReaderBuilder,
+            extractor_builder: ExtractorBuilder,
+            ):
+        self.prefix = prefix
+        self.rbuild = reader_builder
+        self.ebuild = extractor_builder
+
+    def build(self) -> pipeline.Pipeline:
+        """Return a Pipeline instance."""
+        ext2rdr = {}
+
+        for eidx in self.ebuild:
+            # build extractor
+            try:
+                ext = self.ebuild.build(eidx)
+
+            except errors.LoaderError as err: # failed to load extractor; skip
+                logger.error('failed to load extractor: %s', err)
+                continue
+
+            except errors.BuilderError as err: # failed to build instance; skip
+                logger.error(str(err))
+                continue
+
+            try:
+                # get reader required by extractor
+                if ext.CONTENT_READER is not None:
+                    rdr = self.rbuild.build(ext.CONTENT_READER)
+                else:
+                    rdr = None
+                # store extractor
+                ext2rdr[ext] = rdr
+
+            except errors.LoaderError as err: # failed to load reader
+                logger.error('failed to load reader: %s', err)
+
+            except errors.BuilderError as err: # failed to build reader
+                logger.error(str(err))
+
+        return pipeline.Pipeline(self.prefix, ext2rdr)
+
+## EOF ##
diff --git a/bsie/tools/pipeline.py b/bsie/lib/pipeline.py
index 20e8ddf..e5ce1b7 100644
--- a/bsie/tools/pipeline.py
+++ b/bsie/lib/pipeline.py
@@ -4,14 +4,15 @@ Part of the bsie module.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 from collections import defaultdict
 import logging
 import typing
 
 # bsie imports
-from bsie import base
-from bsie.utils import bsfs, node, ns
+from bsie.extractor import Extractor
+from bsie.reader import Reader
+from bsie.utils import bsfs, errors, node, ns
 
 # exports
 __all__: typing.Sequence[str] = (
@@ -43,12 +44,12 @@ class Pipeline():
     _prefix: bsfs.Namespace
 
     # extractor -> reader mapping
-    _ext2rdr: typing.Dict[base.extractor.Extractor, typing.Optional[base.reader.Reader]]
+    _ext2rdr: typing.Dict[Extractor, typing.Optional[Reader]]
 
     def __init__(
             self,
             prefix: bsfs.Namespace,
-            ext2rdr: typing.Dict[base.extractor.Extractor, typing.Optional[base.reader.Reader]]
+            ext2rdr: typing.Dict[Extractor, typing.Optional[Reader]]
             ):
         # store core members
         self._prefix = prefix + FILE_PREFIX
@@ -132,11 +133,11 @@ class Pipeline():
                         for subject, pred, value in ext.extract(subject, content, principals):
                             yield subject, pred, value
 
-                    except base.errors.ExtractorError as err:
+                    except errors.ExtractorError as err:
                         # critical extractor failure.
                         logger.error('%s failed to extract triples from content: %s', ext, err)
 
-            except base.errors.ReaderError as err:
+            except errors.ReaderError as err:
                 # failed to read any content. skip.
                 logger.error('%s failed to read content: %s', rdr, err)
 
diff --git a/bsie/reader/__init__.py b/bsie/reader/__init__.py
index a45f22b..4163d1c 100644
--- a/bsie/reader/__init__.py
+++ b/bsie/reader/__init__.py
@@ -15,5 +15,18 @@ Part of the bsie module.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
+# standard imports
+import typing
 
+# inner-module imports
+from .base import Reader
+from .builder import ReaderBuilder
+
+# exports
+__all__: typing.Sequence[str] = (
+    'Reader',
+    'ReaderBuilder',
+    )
+
+## EOF ##
 ## EOF ##
diff --git a/bsie/base/reader.py b/bsie/reader/base.py
index cbabd36..cbabd36 100644
--- a/bsie/base/reader.py
+++ b/bsie/reader/base.py
diff --git a/bsie/reader/builder.py b/bsie/reader/builder.py
new file mode 100644
index 0000000..bce5397
--- /dev/null
+++ b/bsie/reader/builder.py
@@ -0,0 +1,74 @@
+"""
+
+Part of the bsie module.
+A copy of the license is provided with the project.
+Author: Matthias Baumgartner, 2022
+"""
+# standard imports
+import typing
+
+# bsie imports
+from bsie.utils import bsfs, errors, safe_load, unpack_qualified_name
+
+# inner-module imports
+from . import base
+
+# exports
+__all__: typing.Sequence[str] = (
+    'ReaderBuilder',
+    )
+
+
+## code ##
+
+class ReaderBuilder():
+    """Build `bsie.base.Reader` instances.
+
+    Readers are defined via their qualified class name
+    (e.g., bsie.reader.path.Path) and optional keyword
+    arguments that are passed to the constructor via
+    the *kwargs* argument (name as key, kwargs as value).
+    The ReaderBuilder keeps a cache of previously built
+    reader instances, as they are anyway built with
+    identical keyword arguments.
+
+    """
+
+    # keyword arguments
+    _kwargs: typing.Dict[str, typing.Dict[str, typing.Any]]
+
+    # cached readers
+    _cache: typing.Dict[str, base.Reader]
+
+    def __init__(self, kwargs: typing.Dict[str, typing.Dict[str, typing.Any]]):
+        self._kwargs = kwargs
+        self._cache = {}
+
+    def build(self, name: str) -> base.Reader:
+        """Return an instance for the qualified class name."""
+        # return cached instance
+        if name in self._cache:
+            return self._cache[name]
+
+        # check name and get module/class components
+        module_name, class_name = unpack_qualified_name(name)
+
+        # import reader class
+        cls = safe_load(module_name, class_name)
+
+        # get kwargs
+        kwargs = self._kwargs.get(name, {})
+        if not isinstance(kwargs, dict):
+            raise TypeError(f'expected a kwargs dict, found {bsfs.typename(kwargs)}')
+
+        try: # build, cache, and return instance
+            obj = cls(**kwargs)
+            # cache instance
+            self._cache[name] = obj
+            # return instance
+            return obj
+
+        except Exception as err:
+            raise errors.BuilderError(f'failed to build reader {name} due to {bsfs.typename(err)}: {err}') from err
+
+## EOF ##
diff --git a/bsie/reader/path.py b/bsie/reader/path.py
index d60f187..1ca05a0 100644
--- a/bsie/reader/path.py
+++ b/bsie/reader/path.py
@@ -4,11 +4,11 @@ Part of the bsie module.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import typing
 
-# bsie imports
-from bsie.base import reader
+# inner-module imports
+from . import base
 
 # exports
 __all__: typing.Sequence[str] = (
@@ -18,7 +18,7 @@ __all__: typing.Sequence[str] = (
 
 ## code ##
 
-class Path(reader.Reader):
+class Path(base.Reader):
     """Return the path."""
 
     def __call__(self, path: str) -> str:
diff --git a/bsie/reader/stat.py b/bsie/reader/stat.py
index fc5fb24..706dc47 100644
--- a/bsie/reader/stat.py
+++ b/bsie/reader/stat.py
@@ -4,12 +4,15 @@ Part of the bsie module.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import os
 import typing
 
 # bsie imports
-from bsie.base import errors, reader
+from bsie.utils import errors
+
+# inner-module imports
+from . import base
 
 # exports
 __all__: typing.Sequence[str] = (
@@ -19,7 +22,7 @@ __all__: typing.Sequence[str] = (
 
 ## code ##
 
-class Stat(reader.Reader):
+class Stat(base.Reader):
     """Read and return the filesystem's stat infos."""
 
     def __call__(self, path: str) -> os.stat_result:
diff --git a/bsie/tools/__init__.py b/bsie/tools/__init__.py
deleted file mode 100644
index 803c321..0000000
--- a/bsie/tools/__init__.py
+++ /dev/null
@@ -1,20 +0,0 @@
-"""
-
-Part of the bsie module.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
-# imports
-import typing
-
-# inner-module imports
-from . import builder
-from .pipeline import Pipeline
-
-# exports
-__all__: typing.Sequence[str] = (
-    'builder',
-    'Pipeline',
-    )
-
-## EOF ##
diff --git a/bsie/tools/builder.py b/bsie/tools/builder.py
deleted file mode 100644
index 190d9bf..0000000
--- a/bsie/tools/builder.py
+++ /dev/null
@@ -1,226 +0,0 @@
-"""
-
-Part of the bsie module.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
-# imports
-import importlib
-import logging
-import typing
-
-# bsie imports
-from bsie import base
-from bsie.base import errors
-from bsie.utils import bsfs
-
-# inner-module imports
-from . import pipeline
-
-# exports
-__all__: typing.Sequence[str] = (
-    'ExtractorBuilder',
-    'PipelineBuilder',
-    'ReaderBuilder',
-    )
-
-
-## code ##
-
-logger = logging.getLogger(__name__)
-
-def _safe_load(module_name: str, class_name: str):
-    """Get a class from a module. Raise BuilderError if anything goes wrong."""
-    try:
-        # load the module
-        module = importlib.import_module(module_name)
-    except Exception as err:
-        # cannot import module
-        raise errors.LoaderError(f'cannot load module {module_name}') from err
-
-    try:
-        # get the class from the module
-        cls = getattr(module, class_name)
-    except Exception as err:
-        # cannot find the class
-        raise errors.LoaderError(f'cannot load class {class_name} from module {module_name}') from err
-
-    return cls
-
-
-def _unpack_name(name):
-    """Split a name into its module and class component (dot-separated)."""
-    if not isinstance(name, str):
-        raise TypeError(name)
-    if '.' not in name:
-        raise ValueError('name must be a qualified class name.')
-    module_name, class_name = name[:name.rfind('.')], name[name.rfind('.')+1:]
-    if module_name == '':
-        raise ValueError('name must be a qualified class name.')
-    return module_name, class_name
-
-
-class ReaderBuilder():
-    """Build `bsie.base.Reader` instances.
-
-    Readers are defined via their qualified class name
-    (e.g., bsie.reader.path.Path) and optional keyword
-    arguments that are passed to the constructor via
-    the *kwargs* argument (name as key, kwargs as value).
-    The ReaderBuilder keeps a cache of previously built
-    reader instances, as they are anyway built with
-    identical keyword arguments.
-
-    """
-
-    # keyword arguments
-    _kwargs: typing.Dict[str, typing.Dict[str, typing.Any]]
-
-    # cached readers
-    _cache: typing.Dict[str, base.Reader]
-
-    def __init__(self, kwargs: typing.Dict[str, typing.Dict[str, typing.Any]]):
-        self._kwargs = kwargs
-        self._cache = {}
-
-    def build(self, name: str) -> base.Reader:
-        """Return an instance for the qualified class name."""
-        # return cached instance
-        if name in self._cache:
-            return self._cache[name]
-
-        # check name and get module/class components
-        module_name, class_name = _unpack_name(name)
-
-        # import reader class
-        cls = _safe_load(module_name, class_name)
-
-        # get kwargs
-        kwargs = self._kwargs.get(name, {})
-        if not isinstance(kwargs, dict):
-            raise TypeError(f'expected a kwargs dict, found {bsfs.typename(kwargs)}')
-
-        try: # build, cache, and return instance
-            obj = cls(**kwargs)
-            # cache instance
-            self._cache[name] = obj
-            # return instance
-            return obj
-
-        except Exception as err:
-            raise errors.BuilderError(f'failed to build reader {name} due to {bsfs.typename(err)}: {err}') from err
-
-
-class ExtractorBuilder():
-    """Build `bsie.base.Extractor instances.
-
-    It is permissible to build multiple instances of the same extractor
-    (typically with different arguments), hence the ExtractorBuilder
-    receives a list of build specifications. Each specification is
-    a dict with a single key (extractor's qualified name) and a dict
-    to be used as keyword arguments.
-    Example: [{'bsie.extractor.generic.path.Path': {}}, ]
-
-    """
-
-    # build specifications
-    _specs: typing.List[typing.Dict[str, typing.Dict[str, typing.Any]]]
-
-    def __init__(self, specs: typing.List[typing.Dict[str, typing.Dict[str, typing.Any]]]):
-        self._specs = specs
-
-    def __iter__(self) -> typing.Iterator[int]:
-        """Iterate over extractor specifications."""
-        return iter(range(len(self._specs)))
-
-    def build(self, index: int) -> base.Extractor:
-        """Return an instance of the n'th extractor (n=*index*)."""
-        # get build instructions
-        specs = self._specs[index]
-
-        # check specs structure. expecting[{name: {kwargs}}]
-        if not isinstance(specs, dict):
-            raise TypeError(f'expected a dict, found {bsfs.typename(specs)}')
-        if len(specs) != 1:
-            raise TypeError(f'expected a dict of length one, found {len(specs)}')
-
-        # get name and args from specs
-        name = next(iter(specs.keys()))
-        kwargs = specs[name]
-
-        # check kwargs structure
-        if not isinstance(kwargs, dict):
-            raise TypeError(f'expected a dict, found {bsfs.typename(kwargs)}')
-
-        # check name and get module/class components
-        module_name, class_name = _unpack_name(name)
-
-        # import extractor class
-        cls = _safe_load(module_name, class_name)
-
-        try: # build and return instance
-            return cls(**kwargs)
-
-        except Exception as err:
-            raise errors.BuilderError(f'failed to build extractor {name} due to {bsfs.typename(err)}: {err}') from err
-
-
-class PipelineBuilder():
-    """Build `bsie.tools.pipeline.Pipeline` instances."""
-
-    # Prefix to be used in the Pipeline.
-    prefix: bsfs.Namespace
-
-    # builder for Readers.
-    rbuild: ReaderBuilder
-
-    # builder for Extractors.
-    ebuild: ExtractorBuilder
-
-    def __init__(
-            self,
-            prefix: bsfs.Namespace,
-            reader_builder: ReaderBuilder,
-            extractor_builder: ExtractorBuilder,
-            ):
-        self.prefix = prefix
-        self.rbuild = reader_builder
-        self.ebuild = extractor_builder
-
-    def build(self) -> pipeline.Pipeline:
-        """Return a Pipeline instance."""
-        ext2rdr = {}
-
-        for eidx in self.ebuild:
-            # build extractor
-            try:
-                ext = self.ebuild.build(eidx)
-
-            except errors.LoaderError as err: # failed to load extractor; skip
-                logger.error('failed to load extractor: %s', err)
-                continue
-
-            except errors.BuilderError as err: # failed to build instance; skip
-                logger.error(str(err))
-                continue
-
-            try:
-                # get reader required by extractor
-                if ext.CONTENT_READER is not None:
-                    rdr = self.rbuild.build(ext.CONTENT_READER)
-                else:
-                    rdr = None
-                # store extractor
-                ext2rdr[ext] = rdr
-
-            except errors.LoaderError as err: # failed to load reader
-                logger.error('failed to load reader: %s', err)
-
-            except errors.BuilderError as err: # failed to build reader
-                logger.error(str(err))
-
-        return pipeline.Pipeline(self.prefix, ext2rdr)
-
-
-
-## EOF ##
diff --git a/bsie/utils/__init__.py b/bsie/utils/__init__.py
index 3981dc7..9cb60ed 100644
--- a/bsie/utils/__init__.py
+++ b/bsie/utils/__init__.py
@@ -4,21 +4,24 @@ Part of the bsie module.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import typing
 
 # inner-module imports
 from . import bsfs
+from . import filematcher
 from . import namespaces as ns
 from . import node
-from . import filematcher
+from .loading import safe_load, unpack_qualified_name
 
 # exports
 __all__: typing.Sequence[str] = (
-    'filematcher',
     'bsfs',
+    'filematcher',
     'node',
     'ns',
+    'safe_load',
+    'unpack_qualified_name',
     )
 
 ## EOF ##
diff --git a/bsie/base/errors.py b/bsie/utils/errors.py
index 5fafd5b..5fafd5b 100644
--- a/bsie/base/errors.py
+++ b/bsie/utils/errors.py
diff --git a/bsie/utils/filematcher/parser.py b/bsie/utils/filematcher/parser.py
index 0654742..2f82875 100644
--- a/bsie/utils/filematcher/parser.py
+++ b/bsie/utils/filematcher/parser.py
@@ -7,16 +7,14 @@ Author: Matthias Baumgartner, 2021
 # standard imports
 import typing
 
-# non-standard imports
+# external imports
 import pyparsing
 from pyparsing import printables, alphas8bit, punc8bit, QuotedString, Word, \
                       delimitedList, Or, CaselessKeyword, Group, oneOf, Optional
 
-# bsie imports
-from bsie.base import errors
-
 # inner-module imports
 from . import matcher
+from .. import errors
 
 # exports
 __all__: typing.Sequence[str] = (
diff --git a/bsie/utils/loading.py b/bsie/utils/loading.py
new file mode 100644
index 0000000..eb05c35
--- /dev/null
+++ b/bsie/utils/loading.py
@@ -0,0 +1,54 @@
+"""
+
+Part of the bsie module.
+A copy of the license is provided with the project.
+Author: Matthias Baumgartner, 2022
+"""
+# standard imports
+import importlib
+import typing
+
+# inner-module imports
+from . import errors
+
+# exports
+__all__: typing.Sequence[str] = (
+    'safe_load',
+    'unpack_qualified_name',
+    )
+
+
+## code ##
+
+def safe_load(module_name: str, class_name: str):
+    """Get a class from a module. Raise BuilderError if anything goes wrong."""
+    try:
+        # load the module
+        module = importlib.import_module(module_name)
+    except Exception as err:
+        # cannot import module
+        raise errors.LoaderError(f'cannot load module {module_name}') from err
+
+    try:
+        # get the class from the module
+        cls = getattr(module, class_name)
+    except Exception as err:
+        # cannot find the class
+        raise errors.LoaderError(f'cannot load class {class_name} from module {module_name}') from err
+
+    return cls
+
+
+def unpack_qualified_name(name):
+    """Split a name into its module and class component (dot-separated)."""
+    if not isinstance(name, str):
+        raise TypeError(name)
+    if '.' not in name:
+        raise ValueError('name must be a qualified class name.')
+    module_name, class_name = name[:name.rfind('.')], name[name.rfind('.')+1:]
+    if module_name == '':
+        raise ValueError('name must be a qualified class name.')
+    return module_name, class_name
+
+
+## EOF ##
diff --git a/setup.py b/setup.py
index 8e0efd4..6521593 100644
--- a/setup.py
+++ b/setup.py
@@ -14,7 +14,7 @@ setup(
     url='https://www.igsor.net/projects/blackstar/bsie/',
     download_url='https://pip.igsor.net',
     packages=('bsie', ),
-    install_requires=('rdflib', 'bsfs', 'python-magic'),
+    install_requires=('rdflib', 'bsfs', 'python-magic', 'pyparsing'),
     python_requires=">=3.7",
 )
 
diff --git a/test/base/__init__.py b/test/base/__init__.py
deleted file mode 100644
index e69de29..0000000
--- a/test/base/__init__.py
+++ /dev/null
diff --git a/test/extractor/generic/test_path.py b/test/extractor/generic/test_path.py
index 820f402..778ac5a 100644
--- a/test/extractor/generic/test_path.py
+++ b/test/extractor/generic/test_path.py
@@ -4,11 +4,11 @@ Part of the bsie test suite.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import unittest
 
 # bsie imports
-from bsie.base import extractor
+from bsie.extractor import base
 from bsie.utils import bsfs, node as _node, ns
 
 # objects to test
@@ -29,7 +29,7 @@ class TestPath(unittest.TestCase):
 
     def test_schema(self):
         self.assertEqual(Path().schema,
-            bsfs.schema.Schema.from_string(extractor.SCHEMA_PREAMBLE + '''
+            bsfs.schema.Schema.from_string(base.SCHEMA_PREAMBLE + '''
                 bse:filename rdfs:subClassOf bsfs:Predicate ;
                     rdfs:domain bsfs:File ;
                     rdfs:range xsd:string ;
diff --git a/test/extractor/generic/test_stat.py b/test/extractor/generic/test_stat.py
index 3441438..ff74085 100644
--- a/test/extractor/generic/test_stat.py
+++ b/test/extractor/generic/test_stat.py
@@ -4,12 +4,12 @@ Part of the bsie test suite.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import os
 import unittest
 
 # bsie imports
-from bsie.base import extractor
+from bsie.extractor import base
 from bsie.utils import bsfs, node as _node, ns
 
 # objects to test
@@ -30,7 +30,7 @@ class TestStat(unittest.TestCase):
 
     def test_schema(self):
         self.assertEqual(Stat().schema,
-            bsfs.schema.Schema.from_string(extractor.SCHEMA_PREAMBLE + '''
+            bsfs.schema.Schema.from_string(base.SCHEMA_PREAMBLE + '''
                 bse:filesize rdfs:subClassOf bsfs:Predicate ;
                     rdfs:domain bsfs:File ;
                     rdfs:range xsd:integer ;
diff --git a/test/base/test_extractor.py b/test/extractor/test_base.py
index 30974ef..6a63c59 100644
--- a/test/base/test_extractor.py
+++ b/test/extractor/test_base.py
@@ -4,21 +4,21 @@ Part of the bsie test suite.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import unittest
 
 # bsie imports
 from bsie.utils import bsfs, ns
 
 # objects to test
-from bsie.base import extractor
+from bsie.extractor import base
 
 
 ## code ##
 
-class StubExtractor(extractor.Extractor):
+class StubExtractor(base.Extractor):
     def __init__(self):
-        super().__init__(bsfs.schema.Schema.from_string(extractor.SCHEMA_PREAMBLE + '''
+        super().__init__(bsfs.schema.Schema.from_string(base.SCHEMA_PREAMBLE + '''
             bse:author rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Entity ;
                 rdfs:range xsd:string ;
diff --git a/test/extractor/test_builder.py b/test/extractor/test_builder.py
new file mode 100644
index 0000000..039ea53
--- /dev/null
+++ b/test/extractor/test_builder.py
@@ -0,0 +1,103 @@
+"""
+
+Part of the bsie test suite.
+A copy of the license is provided with the project.
+Author: Matthias Baumgartner, 2022
+"""
+# standard imports
+import unittest
+
+# bsie imports
+from bsie.utils import errors
+
+# objects to test
+from bsie.extractor import ExtractorBuilder
+
+
+## code ##
+
+class TestExtractorBuilder(unittest.TestCase):
+    def test_iter(self):
+        # no specifications
+        self.assertListEqual(list(ExtractorBuilder([])), [])
+        # some specifications
+        builder = ExtractorBuilder([
+            {'bsie.extractor.generic.path.Path': {}},
+            {'bsie.extractor.generic.stat.Stat': {}},
+            {'bsie.extractor.generic.path.Path': {}},
+            ])
+        self.assertListEqual(list(builder), [0, 1, 2])
+
+    def test_build(self):
+        # simple and repeated extractors
+        builder = ExtractorBuilder([
+            {'bsie.extractor.generic.path.Path': {}},
+            {'bsie.extractor.generic.stat.Stat': {}},
+            {'bsie.extractor.generic.path.Path': {}},
+            ])
+        ext = [builder.build(0), builder.build(1), builder.build(2)]
+        import bsie.extractor.generic.path
+        import bsie.extractor.generic.stat
+        self.assertListEqual(ext, [
+            bsie.extractor.generic.path.Path(),
+            bsie.extractor.generic.stat.Stat(),
+            bsie.extractor.generic.path.Path(),
+            ])
+        # out-of-bounds raises KeyError
+        self.assertRaises(IndexError, builder.build, 3)
+
+        # building with args
+        builder = ExtractorBuilder([
+            {'bsie.extractor.generic.constant.Constant': {
+                'schema': '''
+                    bse:author rdfs:subClassOf bsfs:Predicate ;
+                        rdfs:domain bsfs:Entity ;
+                        rdfs:range xsd:string ;
+                        bsfs:unique "true"^^xsd:boolean .
+                    bse:rating rdfs:subClassOf bsfs:Predicate ;
+                        rdfs:domain bsfs:Entity ;
+                        rdfs:range xsd:integer ;
+                        bsfs:unique "true"^^xsd:boolean .
+                    ''',
+                'tuples': [
+                    ('http://bsfs.ai/schema/Entity#author', 'Me, myself, and I'),
+                    ('http://bsfs.ai/schema/Entity#rating', 123),
+                    ],
+            }}])
+        obj = builder.build(0)
+        import bsie.extractor.generic.constant
+        self.assertEqual(obj, bsie.extractor.generic.constant.Constant('''
+                    bse:author rdfs:subClassOf bsfs:Predicate ;
+                        rdfs:domain bsfs:Entity ;
+                        rdfs:range xsd:string ;
+                        bsfs:unique "true"^^xsd:boolean .
+                    bse:rating rdfs:subClassOf bsfs:Predicate ;
+                        rdfs:domain bsfs:Entity ;
+                        rdfs:range xsd:integer ;
+                        bsfs:unique "true"^^xsd:boolean .
+                    ''', [
+            ('http://bsfs.ai/schema/Entity#author', 'Me, myself, and I'),
+            ('http://bsfs.ai/schema/Entity#rating', 123),
+            ]))
+
+        # building with invalid args
+        self.assertRaises(errors.BuilderError, ExtractorBuilder(
+            [{'bsie.extractor.generic.path.Path': {'foo': 123}}]).build, 0)
+        # non-dict build specification
+        self.assertRaises(TypeError, ExtractorBuilder(
+            [('bsie.extractor.generic.path.Path', {})]).build, 0)
+        # multiple keys per build specification
+        self.assertRaises(TypeError, ExtractorBuilder(
+            [{'bsie.extractor.generic.path.Path': {},
+              'bsie.extractor.generic.stat.Stat': {}}]).build, 0)
+        # non-dict value for kwargs
+        self.assertRaises(TypeError, ExtractorBuilder(
+            [{'bsie.extractor.generic.path.Path': 123}]).build, 0)
+
+
+## main ##
+
+if __name__ == '__main__':
+    unittest.main()
+
+## EOF ##
diff --git a/test/lib/test_bsie.py b/test/lib/test_bsie.py
index 771a0c2..52f1d44 100644
--- a/test/lib/test_bsie.py
+++ b/test/lib/test_bsie.py
@@ -4,13 +4,15 @@ Part of the bsie test suite.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import os
 import unittest
 
 # bsie imports
-from bsie.base import extractor
-from bsie.tools import builder
+from bsie.extractor import ExtractorBuilder
+from bsie.extractor.base import SCHEMA_PREAMBLE
+from bsie.lib import PipelineBuilder
+from bsie.reader import ReaderBuilder
 from bsie.utils import bsfs, node, ns
 
 # objects to test
@@ -22,9 +24,9 @@ from bsie.lib.bsie import BSIE
 class TestBSIE(unittest.TestCase):
     def setUp(self):
         # reader builder
-        rbuild = builder.ReaderBuilder({})
+        rbuild = ReaderBuilder({})
         # extractor builder
-        ebuild = builder.ExtractorBuilder([
+        ebuild = ExtractorBuilder([
             {'bsie.extractor.generic.path.Path': {}},
             {'bsie.extractor.generic.stat.Stat': {}},
             {'bsie.extractor.generic.constant.Constant': dict(
@@ -39,7 +41,7 @@ class TestBSIE(unittest.TestCase):
             ])
         # build pipeline
         self.prefix = bsfs.Namespace('http://example.com/local/')
-        pbuild = builder.PipelineBuilder(self.prefix, rbuild, ebuild)
+        pbuild = PipelineBuilder(self.prefix, rbuild, ebuild)
         self.pipeline = pbuild.build()
 
     def test_construction(self):
@@ -50,7 +52,7 @@ class TestBSIE(unittest.TestCase):
             ns.bse.filesize,
             ns.bse.author,
             })
-        self.assertEqual(lib.schema, bsfs.schema.Schema.from_string(extractor.SCHEMA_PREAMBLE + '''
+        self.assertEqual(lib.schema, bsfs.schema.Schema.from_string(SCHEMA_PREAMBLE + '''
             bse:filename rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:File ;
                 rdfs:range xsd:string ;
@@ -77,7 +79,7 @@ class TestBSIE(unittest.TestCase):
             ns.bse.filesize,
             ns.bse.author,
             })
-        self.assertEqual(lib.schema, bsfs.schema.Schema.from_string(extractor.SCHEMA_PREAMBLE + '''
+        self.assertEqual(lib.schema, bsfs.schema.Schema.from_string(SCHEMA_PREAMBLE + '''
             bse:filesize rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:File ;
                 rdfs:range xsd:integer;
@@ -95,7 +97,7 @@ class TestBSIE(unittest.TestCase):
             ns.bse.filesize,
             ns.bse.author,
             })
-        self.assertEqual(lib.schema, bsfs.schema.Schema.from_string(extractor.SCHEMA_PREAMBLE + '''
+        self.assertEqual(lib.schema, bsfs.schema.Schema.from_string(SCHEMA_PREAMBLE + '''
             bse:filename rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:File ;
                 rdfs:range xsd:string ;
@@ -122,7 +124,7 @@ class TestBSIE(unittest.TestCase):
         self.assertSetEqual(set(lib.principals), {
             ns.bse.author,
             })
-        self.assertEqual(lib.schema, bsfs.schema.Schema.from_string(extractor.SCHEMA_PREAMBLE + '''
+        self.assertEqual(lib.schema, bsfs.schema.Schema.from_string(SCHEMA_PREAMBLE + '''
             bse:author rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:Entity ;
                 rdfs:range xsd:string ;
@@ -137,7 +139,7 @@ class TestBSIE(unittest.TestCase):
         self.assertSetEqual(set(lib.principals), {
             ns.bse.filesize,
             })
-        self.assertEqual(lib.schema, bsfs.schema.Schema.from_string(extractor.SCHEMA_PREAMBLE + '''
+        self.assertEqual(lib.schema, bsfs.schema.Schema.from_string(SCHEMA_PREAMBLE + '''
             bse:filesize rdfs:subClassOf bsfs:Predicate ;
                 rdfs:domain bsfs:File ;
                 rdfs:range xsd:integer;
diff --git a/test/lib/test_builder.py b/test/lib/test_builder.py
new file mode 100644
index 0000000..273d620
--- /dev/null
+++ b/test/lib/test_builder.py
@@ -0,0 +1,107 @@
+"""
+
+Part of the bsie test suite.
+A copy of the license is provided with the project.
+Author: Matthias Baumgartner, 2022
+"""
+# standard imports
+import logging
+import unittest
+
+# bsie imports
+from bsie.extractor import ExtractorBuilder
+from bsie.reader import ReaderBuilder
+from bsie.utils import bsfs
+
+# objects to test
+from bsie.lib import PipelineBuilder
+
+
+## code ##
+
+class TestPipelineBuilder(unittest.TestCase):
+    def test_build(self):
+        prefix = bsfs.URI('http://example.com/local/file#')
+        c_schema = '''
+            bse:author rdfs:subClassOf bsfs:Predicate ;
+                rdfs:domain bsfs:Entity ;
+                rdfs:range xsd:string ;
+                bsfs:unique "true"^^xsd:boolean .
+            '''
+        c_tuples = [('http://bsfs.ai/schema/Entity#author', 'Me, myself, and I')]
+        # prepare builders
+        rbuild = ReaderBuilder({})
+        ebuild = ExtractorBuilder([
+            {'bsie.extractor.generic.path.Path': {}},
+            {'bsie.extractor.generic.stat.Stat': {}},
+            {'bsie.extractor.generic.constant.Constant': dict(
+                schema=c_schema,
+                tuples=c_tuples,
+                )},
+            ])
+        # build pipeline
+        builder = PipelineBuilder(prefix, rbuild, ebuild)
+        pipeline = builder.build()
+        # delayed import
+        import bsie.reader.path
+        import bsie.reader.stat
+        import bsie.extractor.generic.path
+        import bsie.extractor.generic.stat
+        import bsie.extractor.generic.constant
+        # check pipeline
+        self.assertDictEqual(pipeline._ext2rdr, {
+            bsie.extractor.generic.path.Path(): bsie.reader.path.Path(),
+            bsie.extractor.generic.stat.Stat(): bsie.reader.stat.Stat(),
+            bsie.extractor.generic.constant.Constant(c_schema, c_tuples): None,
+            })
+
+        # fail to load extractor
+        ebuild_err = ExtractorBuilder([
+            {'bsie.extractor.generic.foo.Foo': {}},
+            {'bsie.extractor.generic.path.Path': {}},
+            ])
+        with self.assertLogs(logging.getLogger('bsie.lib.builder'), logging.ERROR):
+            pipeline = PipelineBuilder(prefix, rbuild, ebuild_err).build()
+            self.assertDictEqual(pipeline._ext2rdr, {
+                bsie.extractor.generic.path.Path(): bsie.reader.path.Path()})
+
+        # fail to build extractor
+        ebuild_err = ExtractorBuilder([
+            {'bsie.extractor.generic.path.Path': {'foo': 123}},
+            {'bsie.extractor.generic.path.Path': {}},
+            ])
+        with self.assertLogs(logging.getLogger('bsie.lib.builder'), logging.ERROR):
+            pipeline = PipelineBuilder(prefix, rbuild, ebuild_err).build()
+            self.assertDictEqual(pipeline._ext2rdr, {
+                bsie.extractor.generic.path.Path(): bsie.reader.path.Path()})
+
+        # fail to load reader
+        with self.assertLogs(logging.getLogger('bsie.lib.builder'), logging.ERROR):
+            # switch reader of an extractor
+            old_reader = bsie.extractor.generic.path.Path.CONTENT_READER
+            bsie.extractor.generic.path.Path.CONTENT_READER = 'bsie.reader.foo.Foo'
+            # build pipeline with invalid reader reference
+            pipeline = PipelineBuilder(prefix, rbuild, ebuild).build()
+            self.assertDictEqual(pipeline._ext2rdr, {
+                bsie.extractor.generic.stat.Stat(): bsie.reader.stat.Stat(),
+                bsie.extractor.generic.constant.Constant(c_schema, c_tuples): None,
+                })
+            # switch back
+            bsie.extractor.generic.path.Path.CONTENT_READER = old_reader
+
+        # fail to build reader
+        rbuild_err = ReaderBuilder({'bsie.reader.stat.Stat': dict(foo=123)})
+        with self.assertLogs(logging.getLogger('bsie.lib.builder'), logging.ERROR):
+            pipeline = PipelineBuilder(prefix, rbuild_err, ebuild).build()
+            self.assertDictEqual(pipeline._ext2rdr, {
+                bsie.extractor.generic.path.Path(): bsie.reader.path.Path(),
+                bsie.extractor.generic.constant.Constant(c_schema, c_tuples): None,
+                })
+
+
+## main ##
+
+if __name__ == '__main__':
+    unittest.main()
+
+## EOF ##
diff --git a/test/tools/test_pipeline.py b/test/lib/test_pipeline.py
index a116a30..c6f7aba 100644
--- a/test/tools/test_pipeline.py
+++ b/test/lib/test_pipeline.py
@@ -4,14 +4,13 @@ Part of the bsie test suite.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import logging
 import os
 import unittest
 
 # bsie imports
-from bsie.base import errors
-from bsie.utils import bsfs, node, ns
+from bsie.utils import bsfs, errors, node, ns
 import bsie.extractor.generic.constant
 import bsie.extractor.generic.path
 import bsie.extractor.generic.stat
@@ -19,7 +18,7 @@ import bsie.reader.path
 import bsie.reader.stat
 
 # objects to test
-from bsie.tools.pipeline import Pipeline
+from bsie.lib.pipeline import Pipeline
 
 
 ## code ##
@@ -140,7 +139,7 @@ class TestPipeline(unittest.TestCase):
                 raise errors.ReaderError('reader error')
 
         pipeline = Pipeline(self.prefix, {bsie.extractor.generic.path.Path(): FaultyReader()})
-        with self.assertLogs(logging.getLogger('bsie.tools.pipeline'), logging.ERROR):
+        with self.assertLogs(logging.getLogger('bsie.lib.pipeline'), logging.ERROR):
             testfile = os.path.join(os.path.dirname(__file__), 'testfile.t')
             p_filename = pipeline.schema.predicate(ns.bse.filename)
             self.assertSetEqual(set(pipeline(testfile, {p_filename})), set())
@@ -151,7 +150,7 @@ class TestPipeline(unittest.TestCase):
                 raise errors.ExtractorError('extractor error')
 
         pipeline = Pipeline(self.prefix, {FaultyExtractor(): bsie.reader.path.Path()})
-        with self.assertLogs(logging.getLogger('bsie.tools.pipeline'), logging.ERROR):
+        with self.assertLogs(logging.getLogger('bsie.lib.pipeline'), logging.ERROR):
             testfile = os.path.join(os.path.dirname(__file__), 'testfile.t')
             p_filename = pipeline.schema.predicate(ns.bse.filename)
             self.assertSetEqual(set(pipeline(testfile, {p_filename})), set())
diff --git a/test/base/test_reader.py b/test/reader/test_base.py
index a907eb9..41f4c29 100644
--- a/test/base/test_reader.py
+++ b/test/reader/test_base.py
@@ -4,16 +4,16 @@ Part of the bsie test suite.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import unittest
 
 # objects to test
-from bsie import base
+from bsie.reader import Reader
 
 
 ## code ##
 
-class StubReader(base.Reader):
+class StubReader(Reader):
     def __call__(self, path):
         raise NotImplementedError()
 
diff --git a/test/reader/test_builder.py b/test/reader/test_builder.py
new file mode 100644
index 0000000..92e9edc
--- /dev/null
+++ b/test/reader/test_builder.py
@@ -0,0 +1,54 @@
+"""
+
+Part of the bsie test suite.
+A copy of the license is provided with the project.
+Author: Matthias Baumgartner, 2022
+"""
+# standard imports
+import unittest
+
+# bsie imports
+from bsie.utils import errors
+
+# objects to test
+from bsie.reader import ReaderBuilder
+
+
+## code ##
+
+class TestReaderBuilder(unittest.TestCase):
+    def test_build(self):
+        builder = ReaderBuilder({'bsie.reader.path.Path': {}})
+        # build configured reader
+        cls = builder.build('bsie.reader.path.Path')
+        import bsie.reader.path
+        self.assertIsInstance(cls, bsie.reader.path.Path)
+        # build unconfigured reader
+        cls = builder.build('bsie.reader.stat.Stat')
+        import bsie.reader.stat
+        self.assertIsInstance(cls, bsie.reader.stat.Stat)
+        # re-build previous reader (test cache)
+        self.assertEqual(cls, builder.build('bsie.reader.stat.Stat'))
+        # test invalid
+        self.assertRaises(TypeError, builder.build, 123)
+        self.assertRaises(TypeError, builder.build, None)
+        self.assertRaises(ValueError, builder.build, '')
+        self.assertRaises(ValueError, builder.build, 'Path')
+        self.assertRaises(errors.BuilderError, builder.build, 'path.Path')
+        # invalid config
+        builder = ReaderBuilder({'bsie.reader.stat.Stat': dict(foo=123)})
+        self.assertRaises(errors.BuilderError, builder.build, 'bsie.reader.stat.Stat')
+        builder = ReaderBuilder({'bsie.reader.stat.Stat': 123})
+        self.assertRaises(TypeError, builder.build, 'bsie.reader.stat.Stat')
+        # no instructions
+        builder = ReaderBuilder({})
+        cls = builder.build('bsie.reader.stat.Stat')
+        self.assertIsInstance(cls, bsie.reader.stat.Stat)
+
+
+## main ##
+
+if __name__ == '__main__':
+    unittest.main()
+
+## EOF ##
diff --git a/test/reader/test_stat.py b/test/reader/test_stat.py
index d12ad9c..fd9fdcd 100644
--- a/test/reader/test_stat.py
+++ b/test/reader/test_stat.py
@@ -4,12 +4,12 @@ Part of the bsie test suite.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import os
 import unittest
 
 # bsie imports
-from bsie.base import errors
+from bsie.utils import errors
 
 # objects to test
 from bsie.reader.stat import Stat
diff --git a/test/tools/__init__.py b/test/tools/__init__.py
deleted file mode 100644
index e69de29..0000000
--- a/test/tools/__init__.py
+++ /dev/null
diff --git a/test/tools/test_builder.py b/test/tools/test_builder.py
deleted file mode 100644
index 62c637c..0000000
--- a/test/tools/test_builder.py
+++ /dev/null
@@ -1,246 +0,0 @@
-"""
-
-Part of the bsie test suite.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
-# imports
-import logging
-import unittest
-
-# bsie imports
-from bsie import base
-from bsie.utils import bsfs
-
-# objects to test
-from bsie.tools.builder import ExtractorBuilder
-from bsie.tools.builder import PipelineBuilder
-from bsie.tools.builder import ReaderBuilder
-from bsie.tools.builder import _safe_load
-from bsie.tools.builder import _unpack_name
-
-
-## code ##
-
-class TestUtils(unittest.TestCase):
-    def test_safe_load(self):
-        # invalid module
-        self.assertRaises(base.errors.LoaderError, _safe_load, 'dBGHMSAYOoKeKMpywDoKZQycENFPvN', 'foobar')
-        self.assertRaises(base.errors.LoaderError, _safe_load, 'dBGHMSAYOoKeKMpywDoKZQycENFPvN.bar', 'foobar')
-        # partially valid module
-        self.assertRaises(base.errors.LoaderError, _safe_load, 'os.foo', 'foobar')
-        # invalid class
-        self.assertRaises(base.errors.LoaderError, _safe_load, 'os.path', 'foo')
-        # valid module and class
-        cls = _safe_load('collections.abc', 'Container')
-        import collections.abc
-        self.assertEqual(cls, collections.abc.Container)
-
-    def test_unpack_name(self):
-        self.assertRaises(TypeError, _unpack_name, 123)
-        self.assertRaises(TypeError, _unpack_name, None)
-        self.assertRaises(ValueError, _unpack_name, '')
-        self.assertRaises(ValueError, _unpack_name, 'path')
-        self.assertRaises(ValueError, _unpack_name, '.Path')
-        self.assertEqual(_unpack_name('path.Path'), ('path', 'Path'))
-        self.assertEqual(_unpack_name('path.foo.bar.Path'), ('path.foo.bar', 'Path'))
-
-
-class TestReaderBuilder(unittest.TestCase):
-    def test_build(self):
-        builder = ReaderBuilder({'bsie.reader.path.Path': {}})
-        # build configured reader
-        cls = builder.build('bsie.reader.path.Path')
-        import bsie.reader.path
-        self.assertIsInstance(cls, bsie.reader.path.Path)
-        # build unconfigured reader
-        cls = builder.build('bsie.reader.stat.Stat')
-        import bsie.reader.stat
-        self.assertIsInstance(cls, bsie.reader.stat.Stat)
-        # re-build previous reader (test cache)
-        self.assertEqual(cls, builder.build('bsie.reader.stat.Stat'))
-        # test invalid
-        self.assertRaises(TypeError, builder.build, 123)
-        self.assertRaises(TypeError, builder.build, None)
-        self.assertRaises(ValueError, builder.build, '')
-        self.assertRaises(ValueError, builder.build, 'Path')
-        self.assertRaises(base.errors.BuilderError, builder.build, 'path.Path')
-        # invalid config
-        builder = ReaderBuilder({'bsie.reader.stat.Stat': dict(foo=123)})
-        self.assertRaises(base.errors.BuilderError, builder.build, 'bsie.reader.stat.Stat')
-        builder = ReaderBuilder({'bsie.reader.stat.Stat': 123})
-        self.assertRaises(TypeError, builder.build, 'bsie.reader.stat.Stat')
-        # no instructions
-        builder = ReaderBuilder({})
-        cls = builder.build('bsie.reader.stat.Stat')
-        self.assertIsInstance(cls, bsie.reader.stat.Stat)
-
-
-
-class TestExtractorBuilder(unittest.TestCase):
-    def test_iter(self):
-        # no specifications
-        self.assertListEqual(list(ExtractorBuilder([])), [])
-        # some specifications
-        builder = ExtractorBuilder([
-            {'bsie.extractor.generic.path.Path': {}},
-            {'bsie.extractor.generic.stat.Stat': {}},
-            {'bsie.extractor.generic.path.Path': {}},
-            ])
-        self.assertListEqual(list(builder), [0, 1, 2])
-
-    def test_build(self):
-        # simple and repeated extractors
-        builder = ExtractorBuilder([
-            {'bsie.extractor.generic.path.Path': {}},
-            {'bsie.extractor.generic.stat.Stat': {}},
-            {'bsie.extractor.generic.path.Path': {}},
-            ])
-        ext = [builder.build(0), builder.build(1), builder.build(2)]
-        import bsie.extractor.generic.path
-        import bsie.extractor.generic.stat
-        self.assertListEqual(ext, [
-            bsie.extractor.generic.path.Path(),
-            bsie.extractor.generic.stat.Stat(),
-            bsie.extractor.generic.path.Path(),
-            ])
-        # out-of-bounds raises KeyError
-        self.assertRaises(IndexError, builder.build, 3)
-
-        # building with args
-        builder = ExtractorBuilder([
-            {'bsie.extractor.generic.constant.Constant': {
-                'schema': '''
-                    bse:author rdfs:subClassOf bsfs:Predicate ;
-                        rdfs:domain bsfs:Entity ;
-                        rdfs:range xsd:string ;
-                        bsfs:unique "true"^^xsd:boolean .
-                    bse:rating rdfs:subClassOf bsfs:Predicate ;
-                        rdfs:domain bsfs:Entity ;
-                        rdfs:range xsd:integer ;
-                        bsfs:unique "true"^^xsd:boolean .
-                    ''',
-                'tuples': [
-                    ('http://bsfs.ai/schema/Entity#author', 'Me, myself, and I'),
-                    ('http://bsfs.ai/schema/Entity#rating', 123),
-                    ],
-            }}])
-        obj = builder.build(0)
-        import bsie.extractor.generic.constant
-        self.assertEqual(obj, bsie.extractor.generic.constant.Constant('''
-                    bse:author rdfs:subClassOf bsfs:Predicate ;
-                        rdfs:domain bsfs:Entity ;
-                        rdfs:range xsd:string ;
-                        bsfs:unique "true"^^xsd:boolean .
-                    bse:rating rdfs:subClassOf bsfs:Predicate ;
-                        rdfs:domain bsfs:Entity ;
-                        rdfs:range xsd:integer ;
-                        bsfs:unique "true"^^xsd:boolean .
-                    ''', [
-            ('http://bsfs.ai/schema/Entity#author', 'Me, myself, and I'),
-            ('http://bsfs.ai/schema/Entity#rating', 123),
-            ]))
-
-        # building with invalid args
-        self.assertRaises(base.errors.BuilderError, ExtractorBuilder(
-            [{'bsie.extractor.generic.path.Path': {'foo': 123}}]).build, 0)
-        # non-dict build specification
-        self.assertRaises(TypeError, ExtractorBuilder(
-            [('bsie.extractor.generic.path.Path', {})]).build, 0)
-        # multiple keys per build specification
-        self.assertRaises(TypeError, ExtractorBuilder(
-            [{'bsie.extractor.generic.path.Path': {},
-              'bsie.extractor.generic.stat.Stat': {}}]).build, 0)
-        # non-dict value for kwargs
-        self.assertRaises(TypeError, ExtractorBuilder(
-            [{'bsie.extractor.generic.path.Path': 123}]).build, 0)
-
-
-
-
-class TestPipelineBuilder(unittest.TestCase):
-    def test_build(self):
-        prefix = bsfs.URI('http://example.com/local/file#')
-        c_schema = '''
-            bse:author rdfs:subClassOf bsfs:Predicate ;
-                rdfs:domain bsfs:Entity ;
-                rdfs:range xsd:string ;
-                bsfs:unique "true"^^xsd:boolean .
-            '''
-        c_tuples = [('http://bsfs.ai/schema/Entity#author', 'Me, myself, and I')]
-        # prepare builders
-        rbuild = ReaderBuilder({})
-        ebuild = ExtractorBuilder([
-            {'bsie.extractor.generic.path.Path': {}},
-            {'bsie.extractor.generic.stat.Stat': {}},
-            {'bsie.extractor.generic.constant.Constant': dict(
-                schema=c_schema,
-                tuples=c_tuples,
-                )},
-            ])
-        # build pipeline
-        builder = PipelineBuilder(prefix, rbuild, ebuild)
-        pipeline = builder.build()
-        # delayed import
-        import bsie.reader.path
-        import bsie.reader.stat
-        import bsie.extractor.generic.path
-        import bsie.extractor.generic.stat
-        import bsie.extractor.generic.constant
-        # check pipeline
-        self.assertDictEqual(pipeline._ext2rdr, {
-            bsie.extractor.generic.path.Path(): bsie.reader.path.Path(),
-            bsie.extractor.generic.stat.Stat(): bsie.reader.stat.Stat(),
-            bsie.extractor.generic.constant.Constant(c_schema, c_tuples): None,
-            })
-
-        # fail to load extractor
-        ebuild_err = ExtractorBuilder([
-            {'bsie.extractor.generic.foo.Foo': {}},
-            {'bsie.extractor.generic.path.Path': {}},
-            ])
-        with self.assertLogs(logging.getLogger('bsie.tools.builder'), logging.ERROR):
-            pipeline = PipelineBuilder(prefix, rbuild, ebuild_err).build()
-            self.assertDictEqual(pipeline._ext2rdr, {
-                bsie.extractor.generic.path.Path(): bsie.reader.path.Path()})
-
-        # fail to build extractor
-        ebuild_err = ExtractorBuilder([
-            {'bsie.extractor.generic.path.Path': {'foo': 123}},
-            {'bsie.extractor.generic.path.Path': {}},
-            ])
-        with self.assertLogs(logging.getLogger('bsie.tools.builder'), logging.ERROR):
-            pipeline = PipelineBuilder(prefix, rbuild, ebuild_err).build()
-            self.assertDictEqual(pipeline._ext2rdr, {
-                bsie.extractor.generic.path.Path(): bsie.reader.path.Path()})
-
-        # fail to load reader
-        with self.assertLogs(logging.getLogger('bsie.tools.builder'), logging.ERROR):
-            # switch reader of an extractor
-            old_reader = bsie.extractor.generic.path.Path.CONTENT_READER
-            bsie.extractor.generic.path.Path.CONTENT_READER = 'bsie.reader.foo.Foo'
-            # build pipeline with invalid reader reference
-            pipeline = PipelineBuilder(prefix, rbuild, ebuild).build()
-            self.assertDictEqual(pipeline._ext2rdr, {
-                bsie.extractor.generic.stat.Stat(): bsie.reader.stat.Stat(),
-                bsie.extractor.generic.constant.Constant(c_schema, c_tuples): None,
-                })
-            # switch back
-            bsie.extractor.generic.path.Path.CONTENT_READER = old_reader
-
-        # fail to build reader
-        rbuild_err = ReaderBuilder({'bsie.reader.stat.Stat': dict(foo=123)})
-        with self.assertLogs(logging.getLogger('bsie.tools.builder'), logging.ERROR):
-            pipeline = PipelineBuilder(prefix, rbuild_err, ebuild).build()
-            self.assertDictEqual(pipeline._ext2rdr, {
-                bsie.extractor.generic.path.Path(): bsie.reader.path.Path(),
-                bsie.extractor.generic.constant.Constant(c_schema, c_tuples): None,
-                })
-
-
-## main ##
-
-if __name__ == '__main__':
-    unittest.main()
-
-## EOF ##
diff --git a/test/tools/testfile.t b/test/tools/testfile.t
deleted file mode 100644
index 3b18e51..0000000
--- a/test/tools/testfile.t
+++ /dev/null
@@ -1 +0,0 @@
-hello world
diff --git a/test/utils/filematcher/test_parser.py b/test/utils/filematcher/test_parser.py
index a81d2ed..c594747 100644
--- a/test/utils/filematcher/test_parser.py
+++ b/test/utils/filematcher/test_parser.py
@@ -4,11 +4,11 @@ Part of the bsie test suite.
 A copy of the license is provided with the project.
 Author: Matthias Baumgartner, 2022
 """
-# imports
+# standard imports
 import unittest
 
-# inner-module imports
-from bsie.base import errors
+# bsie imports
+from bsie.utils import errors
 from bsie.utils.filematcher import matcher
 
 # objects to test
diff --git a/test/utils/test_loading.py b/test/utils/test_loading.py
new file mode 100644
index 0000000..58ff166
--- /dev/null
+++ b/test/utils/test_loading.py
@@ -0,0 +1,48 @@
+"""
+
+Part of the bsie test suite.
+A copy of the license is provided with the project.
+Author: Matthias Baumgartner, 2022
+"""
+# standard imports
+import unittest
+
+# bsie imports
+from bsie.utils import errors
+
+# objects to test
+from bsie.utils.loading import safe_load, unpack_qualified_name
+
+
+## code ##
+
+class TestUtils(unittest.TestCase):
+    def test_safe_load(self):
+        # invalid module
+        self.assertRaises(errors.LoaderError, safe_load, 'dBGHMSAYOoKeKMpywDoKZQycENFPvN', 'foobar')
+        self.assertRaises(errors.LoaderError, safe_load, 'dBGHMSAYOoKeKMpywDoKZQycENFPvN.bar', 'foobar')
+        # partially valid module
+        self.assertRaises(errors.LoaderError, safe_load, 'os.foo', 'foobar')
+        # invalid class
+        self.assertRaises(errors.LoaderError, safe_load, 'os.path', 'foo')
+        # valid module and class
+        cls = safe_load('collections.abc', 'Container')
+        import collections.abc
+        self.assertEqual(cls, collections.abc.Container)
+
+    def test_unpack_qualified_name(self):
+        self.assertRaises(TypeError, unpack_qualified_name, 123)
+        self.assertRaises(TypeError, unpack_qualified_name, None)
+        self.assertRaises(ValueError, unpack_qualified_name, '')
+        self.assertRaises(ValueError, unpack_qualified_name, 'path')
+        self.assertRaises(ValueError, unpack_qualified_name, '.Path')
+        self.assertEqual(unpack_qualified_name('path.Path'), ('path', 'Path'))
+        self.assertEqual(unpack_qualified_name('path.foo.bar.Path'), ('path.foo.bar', 'Path'))
+
+
+## main ##
+
+if __name__ == '__main__':
+    unittest.main()
+
+## EOF ##