SPARQL queries and user defined vocabulary

[Olivier Inizan]

Hi there,

I am trying to play with rdflib and a (my) user defined vocabulary (name: ODE).
To do that I have generated a class namespace/_ODE.py derived from DefinedNamespace:
  1 from rdflib.term import URIRef
  2 from rdflib.namespace import DefinedNamespace, Namespace
  3
  4
  5 class ODE(DefinedNamespace):
  6     """          
  7     DESCRIPTION_EDIT_ME_!
  8
  9     Generated from: SOURCE_RDF_FILE_EDIT_ME_!
 10     Date: 2022-05-02 08:38:55.619901
 11     """              
 12
 13     _fail = True
 14
 15     Function: URIRef
 16     Equation: URIRef
 17     hasDerivative: URIRef
 18     Polynomial: URIRef    
 19     Ode: URIRef
 20
 21     _NS = Namespace("ode#")
 22

As all the new "classes" of the ODE vocabulary are a specialization of the class "Seq" I have created the module rdflib/ode.py:

  1 from rdflib import Seq
  2 from rdflib.namespace import RDF,ODE,MATH
  3
  4 __all__ = ["Function", "Equation","Polynomial","Ode"]
  5
  6
  7 class Ode(Seq):
  8     def __init__(self, graph, uri, seq=[], rtype="Ode"):
  9         """Creates a Container
 10
 11         :param graph: a Graph instance
 12         :param uri: URI or Blank Node of the Container
 13         :param seq: the elements of the Container
 14         :param rtype: the type of Container, one of "Bag", "Seq" or "Alt"
 15         """
 16
 17         self.graph = graph
 18         self.uri = uri or BNode()
 19         self._len = 0
 20         self._rtype = rtype  # rdf:Bag or rdf:Seq or rdf:Alt
 21
 22         self.append_multiple(seq)
 23
 24         # adding triple corresponding to container type
 25         self.graph.add((self.uri, RDF.type, ODE[self._rtype]))
 26
 27 class Function(Ode):
 28     def __init__(self, graph, uri, seq=[]):
 29         Ode.__init__(self, graph, uri, seq, "Function")
 30
 31
 32 class Equation(Ode):
 33     def __init__(self, graph, uri, seq=[]):
 34         Ode.__init__(self, graph, uri, seq, "Equation")
 35
 36 class Polynomial(Ode):
 37     def __init__(self, graph, uri, seq=[]):
 38         Ode.__init__(self, graph, uri, seq, "Polynomial")

With these two classes I can generate a RDF file in a declarative way.
For example we can create the Function c(t):
1  from rdflib import Graph, URIRef, RDF, BNode, RDFS, Literal, Seq, Bag, Function, Equation, Times, Minus, Polynomial, Ode
2  from rdflib.namespace import ODE, MATH
3
4  # the time t
5  t = BNode("t")
6  graph.add((t,RDFS.label,Literal("t")))
7
8  c_of_t_label = BNode("c")
9  graph.add((c_of_t_label,RDFS.label,Literal("c")))
10 c_of_t_bn = BNode("c_of_t")
11
12 Function(graph,c_of_t_bn,[c_of_t_label,t])

And we obtain the following RDF:
_:c rdfs:label "c" .
_:t rdfs:label "t" .
_:c_of_t a ode:Function ;
    rdf:_1 _:c ;
    rdf:_2 _:t .

So far, so good. Now I want to execute a SPARQL query on this rdf to retrieve the function.
                                                                                                                                                                         
1 import rdflib
2
3 from rdflib import Graph, URIRef, RDF, BNode, RDFS, Literal, Seq, Bag, Function, Equation, Times, Minus, Polynomial, Ode
4 from rdflib.namespace import ODE, MATH
5
6 def main():
7     g = rdflib.Graph()
8     g.parse("ode_spe", format="ttl")
9    
10    
11     function = ODE.Function
12    
13     query_test= "SELECT ?e WHERE {?e rdf:type ode:Function . }"
14     qres = g.query(query_test)
15    
16     print (len(qres))
17 if __name__ == "__main__":
18     main()

But I have no results.
I probably do not do the right thing with ode:Function.

I have two questions:
- Is it the right way to add a user defined vocabulary ?
- And what can I do to retrieve the function with a SPARQL query

Thank for your help.

Olivier

[Donny Winston]

Hi Oliver,

I have an idea for why this may not be working for you, but I'd rather respond to a question on StackOverflow (https://stackoverflow.com/questions/ask) tagged with the "rdflib" tag added (rdflib should autocomplete in the tags input), as this email list is for technical matters relating to the RDFLib software, not usage questions. 

I just checked that I am subscribed to email notifications for new [rdflib] questions (https://stackoverflow.com/questions/tagged/rdflib) on StackOverflow. If I don't respond to your question soon, feel free to email me directly to get on it. :)

Best,

Donny

[Olivier Inizan]

OK thanks Donny.