3 files changed, 140 insertions, 0 deletions
diff --git a/bsfs/namespace/__init__.py b/bsfs/namespace/__init__.py
new file mode 100644
index 0000000..98d472f
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+++ b/bsfs/namespace/__init__.py
@@ -0,0 +1,21 @@
+"""
+
+Part of the BlackStar filesystem (bsfs) module.
+A copy of the license is provided with the project.
+Author: Matthias Baumgartner, 2022
+"""
+# imports
+import typing
+
+# inner-module imports
+from . import predefined as ns
+from .namespace import ClosedNamespace, Namespace
+
+# exports
+__all__: typing.Sequence[str] = (
+    'ClosedNamespace',
+    'Namespace',
+    'ns',
+    )
+
+## EOF ##
diff --git a/bsfs/namespace/namespace.py b/bsfs/namespace/namespace.py
new file mode 100644
index 0000000..8080f5d
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+++ b/bsfs/namespace/namespace.py
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+"""
+
+Part of the BlackStar filesystem (bsfs) module.
+A copy of the license is provided with the project.
+Author: Matthias Baumgartner, 2022
+"""
+# imports
+import typing
+
+# bsfs imports
+from bsfs.utils import URI, typename
+
+# exports
+__all__: typing.Sequence[str] = (
+    'ClosedNamespace',
+    'Namespace',
+    )
+
+
+## code ##
+
+class Namespace():
+    """A namespace consists of a common prefix that is used in a set of URIs.
+
+    Note that the prefix must include the separator between
+    path and fragment (typically a '#' or a '/').
+    """
+
+    # namespace prefix.
+    prefix: URI
+
+    def __init__(self, prefix: URI):
+        self.prefix = URI(prefix)
+
+    def __eq__(self, other: typing.Any) -> bool:
+        return isinstance(other, type(self)) and self.prefix == other.prefix
+
+    def __hash__(self) -> int:
+        return hash((type(self), self.prefix))
+
+    def __str__(self) -> str:
+        return f'{typename(self)}({self.prefix})'
+
+    def __repr__(self) -> str:
+        return f'{typename(self)}({self.prefix})'
+
+    def __getattr__(self, fragment: str) -> URI:
+        """Return prefix + fragment."""
+        return URI(self.prefix + fragment)
+
+    def __getitem__(self, fragment: str) -> URI:
+        """Alias for getattr(self, fragment)."""
+        return self.__getattr__(fragment)
+
+
+class ClosedNamespace(Namespace):
+    """Namespace that covers a restricted set of URIs."""
+
+    # set of permissible fragments.
+    fragments: typing.Set[str]
+
+    def __init__(self, prefix: URI, *args: str):
+        super().__init__(prefix)
+        self.fragments = set(args)
+
+    def __eq__(self, other: typing.Any) -> bool:
+        return super().__eq__(other) and self.fragments == other.fragments
+
+    def __hash__(self) -> int:
+        return hash((type(self), self.prefix, tuple(sorted(self.fragments))))
+
+    def __getattr__(self, fragment: str) -> URI:
+        """Return prefix + fragment.
+        Raises a KeyError if the fragment is not allowed in this namespace.
+        """
+        if fragment not in self.fragments:
+            raise KeyError('fragment')
+        return super().__getattr__(fragment)
+
+## EOF ##
diff --git a/bsfs/namespace/predefined.py b/bsfs/namespace/predefined.py
new file mode 100644
index 0000000..21ca560
--- /dev/null
+++ b/bsfs/namespace/predefined.py
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+"""
+
+Part of the BlackStar filesystem (bsfs) module.
+A copy of the license is provided with the project.
+Author: Matthias Baumgartner, 2022
+"""
+# imports
+import typing
+
+# bsfs imports
+from bsfs.utils import URI
+
+# inner-module imports
+from . import namespace
+
+# essential bsfs namespaces
+bsfs: namespace.Namespace = namespace.Namespace(URI('http://bsfs.ai/schema/'))
+
+# additional bsfs namespaces
+bse: namespace.Namespace = namespace.Namespace(URI('http://bsfs.ai/schema/Entity#'))
+bsm: namespace.Namespace = namespace.Namespace(URI('http://bsfs.ai/schema/Meta#'))
+
+# generic namespaces
+rdf: namespace.Namespace = namespace.Namespace(URI('http://www.w3.org/1999/02/22-rdf-syntax-ns#'))
+rdfs: namespace.Namespace = namespace.Namespace(URI('http://www.w3.org/2000/01/rdf-schema#'))
+schema: namespace.Namespace = namespace.Namespace(URI('http://schema.org/'))
+xsd: namespace.Namespace = namespace.Namespace(URI('http://www.w3.org/2001/XMLSchema#'))
+
+__all__: typing.Sequence[str] = (
+    'bse',
+    'bsfs',
+    'bsm',
+    'rdf',
+    'rdfs',
+    'schema',
+    'xsd',
+    )
+
+## EOF ##