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#!/usr/bin/env python
# -*- coding: utf-8 -*-
__doc__ = """
A Describer is a stateful utility for creating RDF statements in a
semi-declarative manner. It has methods for creating literal values, rel and
rev resource relations (somewhat resembling RDFa).
The `Describer.rel` and `Describer.rev` methods return a context manager which sets the current
about to the referenced resource for the context scope (for use with the
``with`` statement).
Full example in the ``to_rdf`` method below::
>>> import datetime
>>> from rdflib.graph import Graph
>>> from rdflib.namespace import Namespace, RDFS, FOAF
>>>
>>> ORG_URI = "http://example.org/"
>>>
>>> CV = Namespace("http://purl.org/captsolo/resume-rdf/0.2/cv#")
>>>
>>> class Person:
... def __init__(self):
... self.first_name = u"Some"
... self.last_name = u"Body"
... self.username = "some1"
... self.presentation = u"Just a Python & RDF hacker."
... self.image = "/images/persons/" + self.username + ".jpg"
... self.site = "http://example.net/"
... self.start_date = datetime.date(2009, 9, 4)
... def get_full_name(self):
... return u" ".join([self.first_name, self.last_name])
... def get_absolute_url(self):
... return "/persons/" + self.username
... def get_thumbnail_url(self):
... return self.image.replace('.jpg', '-thumb.jpg')
...
... def to_rdf(self):
... graph = Graph()
... graph.bind('foaf', FOAF)
... graph.bind('cv', CV)
... lang = 'en'
... d = Describer(graph, base=ORG_URI)
... d.about(self.get_absolute_url()+'#person')
... d.rdftype(FOAF.Person)
... d.value(FOAF.name, self.get_full_name())
... d.value(FOAF.givenName, self.first_name)
... d.value(FOAF.familyName, self.last_name)
... d.rel(FOAF.homepage, self.site)
... d.value(RDFS.comment, self.presentation, lang=lang)
... with d.rel(FOAF.depiction, self.image):
... d.rdftype(FOAF.Image)
... d.rel(FOAF.thumbnail, self.get_thumbnail_url())
... with d.rev(CV.aboutPerson):
... d.rdftype(CV.CV)
... with d.rel(CV.hasWorkHistory):
... d.value(CV.startDate, self.start_date)
... d.rel(CV.employedIn, ORG_URI+"#company")
... return graph
...
>>> person_graph = Person().to_rdf()
>>> expected = Graph().parse(data='''<?xml version="1.0" encoding="utf-8"?>
... <rdf:RDF
... xmlns:foaf="http://xmlns.com/foaf/0.1/"
... xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
... xmlns:cv="http://purl.org/captsolo/resume-rdf/0.2/cv#"
... xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
... <foaf:Person rdf:about="http://example.org/persons/some1#person">
... <foaf:name>Some Body</foaf:name>
... <foaf:givenName>Some</foaf:givenName>
... <foaf:familyName>Body</foaf:familyName>
... <foaf:depiction>
... <foaf:Image
... rdf:about=
... "http://example.org/images/persons/some1.jpg">
... <foaf:thumbnail
... rdf:resource=
... "http://example.org/images/persons/some1-thumb.jpg"/>
... </foaf:Image>
... </foaf:depiction>
... <rdfs:comment xml:lang="en">
... Just a Python & RDF hacker.
... </rdfs:comment>
... <foaf:homepage rdf:resource="http://example.net/"/>
... </foaf:Person>
... <cv:CV>
... <cv:aboutPerson
... rdf:resource="http://example.org/persons/some1#person">
... </cv:aboutPerson>
... <cv:hasWorkHistory>
... <rdf:Description>
... <cv:startDate
... rdf:datatype="http://www.w3.org/2001/XMLSchema#date"
... >2009-09-04</cv:startDate>
... <cv:employedIn rdf:resource="http://example.org/#company"/>
... </rdf:Description>
... </cv:hasWorkHistory>
... </cv:CV>
... </rdf:RDF>
... ''', format="xml")
>>>
>>> from rdflib.compare import isomorphic
>>> isomorphic(person_graph, expected) #doctest: +SKIP
True
"""
from contextlib import contextmanager
from rdflib.graph import Graph
from rdflib.namespace import RDF
from rdflib.term import BNode, Identifier, Literal, URIRef
class Describer:
def __init__(self, graph=None, about=None, base=None):
if graph is None:
graph = Graph()
self.graph = graph
self.base = base
self._subjects = []
self.about(about or None)
def about(self, subject, **kws):
"""
Sets the current subject. Will convert the given object into an
``URIRef`` if it's not an ``Identifier``.
Usage::
>>> d = Describer()
>>> d._current() #doctest: +ELLIPSIS
rdflib.term.BNode(...)
>>> d.about("http://example.org/")
>>> d._current()
rdflib.term.URIRef(u'http://example.org/')
"""
kws.setdefault("base", self.base)
subject = cast_identifier(subject, **kws)
if self._subjects:
self._subjects[-1] = subject
else:
self._subjects.append(subject)
def value(self, p, v, **kws):
"""
Set a literal value for the given property. Will cast the value to an
``Literal`` if a plain literal is given.
Usage::
>>> from rdflib import URIRef
>>> from rdflib.namespace import RDF, RDFS
>>> d = Describer(about="http://example.org/")
>>> d.value(RDFS.label, "Example")
>>> d.graph.value(URIRef('http://example.org/'), RDFS.label)
rdflib.term.Literal(u'Example')
"""
v = cast_value(v, **kws)
self.graph.add((self._current(), p, v))
def rel(self, p, o=None, **kws):
"""Set an object for the given property. Will convert the given object
into an ``URIRef`` if it's not an ``Identifier``. If none is given, a
new ``BNode`` is used.
Returns a context manager for use in a ``with`` block, within which the
given object is used as current subject.
Usage::
>>> from rdflib import URIRef
>>> from rdflib.namespace import RDF, RDFS
>>> d = Describer(about="/", base="http://example.org/")
>>> _ctxt = d.rel(RDFS.seeAlso, "/about")
>>> d.graph.value(URIRef('http://example.org/'), RDFS.seeAlso)
rdflib.term.URIRef(u'http://example.org/about')
>>> with d.rel(RDFS.seeAlso, "/more"):
... d.value(RDFS.label, "More")
>>> (URIRef('http://example.org/'), RDFS.seeAlso,
... URIRef('http://example.org/more')) in d.graph
True
>>> d.graph.value(URIRef('http://example.org/more'), RDFS.label)
rdflib.term.Literal(u'More')
"""
kws.setdefault("base", self.base)
p = cast_identifier(p)
o = cast_identifier(o, **kws)
self.graph.add((self._current(), p, o))
return self._subject_stack(o)
def rev(self, p, s=None, **kws):
"""
Same as ``rel``, but uses current subject as *object* of the relation.
The given resource is still used as subject in the returned context
manager.
Usage::
>>> from rdflib import URIRef
>>> from rdflib.namespace import RDF, RDFS
>>> d = Describer(about="http://example.org/")
>>> with d.rev(RDFS.seeAlso, "http://example.net/"):
... d.value(RDFS.label, "Net")
>>> (URIRef('http://example.net/'), RDFS.seeAlso,
... URIRef('http://example.org/')) in d.graph
True
>>> d.graph.value(URIRef('http://example.net/'), RDFS.label)
rdflib.term.Literal(u'Net')
"""
kws.setdefault("base", self.base)
p = cast_identifier(p)
s = cast_identifier(s, **kws)
self.graph.add((s, p, self._current()))
return self._subject_stack(s)
def rdftype(self, t):
"""
Shorthand for setting rdf:type of the current subject.
Usage::
>>> from rdflib import URIRef
>>> from rdflib.namespace import RDF, RDFS
>>> d = Describer(about="http://example.org/")
>>> d.rdftype(RDFS.Resource)
>>> (URIRef('http://example.org/'),
... RDF.type, RDFS.Resource) in d.graph
True
"""
self.graph.add((self._current(), RDF.type, t))
def _current(self):
return self._subjects[-1]
@contextmanager
def _subject_stack(self, subject):
self._subjects.append(subject)
yield None
self._subjects.pop()
def cast_value(v, **kws):
if not isinstance(v, Literal):
v = Literal(v, **kws)
return v
def cast_identifier(ref, **kws):
ref = ref or BNode()
if not isinstance(ref, Identifier):
ref = URIRef(ref, **kws)
return ref
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