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Ontologies
SPARQLFederator needs two OWL2 ontologies in order to perform query expansion, the domain ontology and the federation ontology.
This ontology contains T-box knowledge about the domain of discourse, that is, the classes, properties and axioms that are relevant to your problem. See the page SPARQLFederator Semantics to see which types of inference SPARQLFederator can deal with.
This ontology describe the relevant endpoints and which classes and properties from the domain ontology they contain information about. It must follow the conventions below.
- Each integrated endpoint should have an equivalent instance of class :System;
- Property :systemHasSparqlEndpoint relates an instance of System to the endpoint URL (as if the endpoint URL "http://test.com:8080/sparql" were an instance URI);
- Property :systemImplementsClass relates an instance of System to a class on the domain ontology, meaning that this class can be queried on that endpoint;
(default namespace : http://www.cipe.accamargo.org.br/ontologias/ontocloud2.owl)
As you see, you need to relate an instance of the System class to classes by the property systemImplementsClass - that makes this ontology undecidable. However, only SubClassOf semantics are needed by SPARQLFederator, so this poses no problem.