OWL File Query Execution Error in RDFLIB

Question

I'm trying to make SPARQL queries on an OWL file (see pastebin) but it is the first time I'm dealing with an OWL file, so I used RDFLIB in Python to make SPARQL queries. When i run the code I get an error (shown below code) which I do not understand. What could be causing this?

Code

import rdflib
graph = rdflib.Graph()
prefix="""PREFIX  dc:<http://purl.org/dc/elements/1.1/>
PREFIX  foaf: <http://xmlns.com/foaf/0.1/>
PREFIX  olia-ar: <http://purl.org/olia/arabic_khoja.owl#>
PREFIX  dcterms: <http://purl.org/dc/terms/>
PREFIX  rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX  owl:  <http://www.w3.org/2002/07/owl#>
PREFIX  xsd:  <http://www.w3.org/2001/XMLSchema#>
PREFIX  lexvo: <http://lexvo.org/id/iso639-3/>
PREFIX  rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX  p1: <http://protege.stanford.edu/plugins/owl/protege#>
PREFIX  base: <http://www.owl-ontologies.com/unnamed.owl#>
PREFIX xmlns:<http://www.owl-ontologies.com/unnamed.owl#>
"""
queryString = prefix+"\n"+"""SELECT ?animalClass
WHERE {
      ?animal :Has_Usage "Ride";
              rdf:type ?animalClass.
      }"""
graph.parse('animal.owl')
result = graph.query(queryString)
for row in result:
    print row

Error

Traceback (most recent call last):
  File "D:\Python27\animal.py", line 22, in <module>
    result = graph.query(queryString)
  File "build\bdist.win32\egg\rdflib\graph.py", line 1007, in query
    query_object, initBindings, initNs, **kwargs))
  File "D:\Python27\lib\site-packages\rdfextras-0.4-py2.7.egg\rdfextras\sparql\processor.py", line 49, in query
    loadContexts=loadContexts)
  File "D:\Python27\lib\site-packages\rdfextras-0.4-py2.7.egg\rdfextras\sparql\algebra.py", line 358, in TopEvaluate
    None)
  File "D:\Python27\lib\site-packages\rdfextras-0.4-py2.7.egg\rdfextras\sparql\algebra.py", line 179, in ReduceToAlgebra
    right = ReduceGraphPattern(right,prolog)
  File "D:\Python27\lib\site-packages\rdfextras-0.4-py2.7.egg\rdfextras\sparql\algebra.py", line 63, in ReduceGraphPattern
    bgp=BasicGraphPattern(list(unRollTripleItems(triple,prolog)),prolog)
  File "D:\Python27\lib\site-packages\rdfextras-0.4-py2.7.egg\rdfextras\sparql\evaluate.py", line 301, in unRollTripleItems
    for item in unRollRDFTerm(items, queryProlog):
  File "D:\Python27\lib\site-packages\rdfextras-0.4-py2.7.egg\rdfextras\sparql\evaluate.py", line 281, in unRollRDFTerm
    convertTerm(propVal.property, queryProlog),
  File "D:\Python27\lib\site-packages\rdfextras-0.4-py2.7.egg\rdfextras\sparql\evaluate.py", line 151, in convertTerm
    base = queryProlog.prefixBindings[u'']
KeyError: u''

Answer 1

The obvious error I can see is that you use the prefixed name :Has_Usage but you haven't defined an empty prefix i.e.

PREFIX : <http://example.org/ns#>

I guess this is maybe what you were trying to do with the PREFIX xmlns: declaration?