Proposal to resolve ISSUE-81 (reification in netagive property assertions)

Hello,

Here is a proposal for resolving this issue. Instead of using the RDF reification vocabulary, we should introduce four new
vocabulary items: owl:sourceIndividual, owl:targetIndividual, owl:assertionProperty, and owl:targetValue. Then, negative assertions
on object properties would be serialized as follows:

  NegativePropertyAssertion( my:prop my:i1 my:i2 )

==>

  _:x rdf:type owl:NegativePropertyAssertion
  _:x owl:sourceIndividual my:i1
  _:x owl:assertionProperty my:prop
  _:x owl:targetIndividual my:i2


Similarly, negative assertions on data properties would be serialized as follows:

  NegativePropertyAssertion( my:prop my:i1 "const"^^xsd:string )

==>

  _:x rdf:type owl:NegativePropertyAssertion
  _:x owl:sourceIndividual my:i1
  _:x owl:assertionProperty my:prop
  _:x owl:targetValue "const"^^xsd:string

Please let me know how you feel about this.

Regards,

	Boris