blob: 0b82b6b43b7bd77cb2d8ed65fa8d17124f070f1f (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
|
"""
This example shows how a custom evaluation function can be added to
handle certain SPARQL Algebra elements
A custom function is added that adds subClassOf "inference" when
asking for rdf:type triples.
Here the custom eval function is added manually, normally you would use
setuptools and entry_points to do it:
i.e. in your setup.py:
entry_points = {
'rdf.plugins.sparqleval': [
'myfunc = mypackage:MyFunction',
],
}
"""
import rdflib.plugins.sparql.paths
import rdflib
from rdflib.plugins.sparql.evaluate import evalBGP
from rdflib.namespace import FOAF
inferredSubClass = \
rdflib.RDFS.subClassOf % '*' # any number of rdfs.subClassOf
def customEval(ctx, part):
"""
Rewrite triple patterns to get super-classes
"""
if part.name == 'BGP':
# rewrite triples
triples = []
for t in part.triples:
if t[1] == rdflib.RDF.type:
bnode = rdflib.BNode()
triples.append((t[0], t[1], bnode))
triples.append((bnode, inferredSubClass, t[2]))
else:
triples.append(t)
# delegate to normal evalBGP
return evalBGP(ctx, triples)
raise NotImplementedError()
# add function directly, normally we would use setuptools and entry_points
rdflib.plugins.sparql.CUSTOM_EVALS['exampleEval'] = customEval
g = rdflib.Graph()
g.load("foaf.rdf")
# Add the subClassStmt so that we can query for it!
g.add((FOAF.Person,
rdflib.RDFS.subClassOf,
FOAF.Agent))
# Find all FOAF Agents
for x in g.query(
'PREFIX foaf: <%s> SELECT * WHERE { ?s a foaf:Agent . }' % FOAF):
print x
|
