/usr/share/doc/python-rdflib-doc/examples/transitive.py is in python-rdflib-doc 4.1.2-3.
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An example illustrating how to use the
:meth:`~rdflib.graph.Graph.transitive_subjects` and
:meth:`~rdflib.graph.Graph.transitive_objects` graph methods
Formal definition
^^^^^^^^^^^^^^^^^^
The :meth:`~rdflib.graph.Graph.transitive_objects` method finds all
nodes such that there is a path from subject to one of those nodes
using only the predicate property in the triples. The
:meth:`~rdflib.graph.Graph.transitive_subjects` method is similar; it
finds all nodes such that there is a path from the node to the object
using only the predicate property.
Informal description, with an example
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In brief, :meth:`~rdflib.graph.Graph.transitive_objects` walks forward
in a graph using a particular property, and
:meth:`~rdflib.graph.Graph.transitive_subjects` walks backward. A good
example uses a property ``ex:parent``, the semantics of which are
biological parentage. The
:meth:`~rdflib.graph.Graph.transitive_objects` method would get all
the ancestors of a particular person (all nodes such that there is a
parent path between the person and the object). The
:meth:`~rdflib.graph.Graph.transitive_subjects` method would get all
the descendants of a particular person (all nodes such that there is a
parent path between the node and the person). So, say that your URI is
``ex:person``.
This example would get all of your (known) ancestors, and then get all
the (known) descendants of your maternal grandmother.
.. warning:: The :meth:`transitive_objects` method has the start node
as the *first* argument, but the :meth:`transitive_subjects`
method has the start node as the *second* argument.
User-defined transitive closures
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The method :meth:`~rdflib.graph.Graph.transitiveClosure` returns
transtive closures of user-defined functions.
"""
if __name__=='__main__':
from rdflib import ConjunctiveGraph, URIRef
person = URIRef('ex:person')
dad = URIRef('ex:d')
mom = URIRef('ex:m')
momOfDad = URIRef('ex:gm0')
momOfMom = URIRef('ex:gm1')
dadOfDad = URIRef('ex:gf0')
dadOfMom = URIRef('ex:gf1')
parent = URIRef('ex:parent')
g = ConjunctiveGraph()
g.add((person, parent, dad))
g.add((person, parent, mom))
g.add((dad, parent, momOfDad))
g.add((dad, parent, dadOfDad))
g.add((mom, parent, momOfMom))
g.add((mom, parent, dadOfMom))
print "Parents, forward from `ex:person`:"
for i in g.transitive_objects(person, parent):
print i
print "Parents, *backward* from `ex:gm1`:"
for i in g.transitive_subjects(parent, momOfMom):
print i
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