The Ontology Problem: A Definition with Commentary" "If the Ontology Integration Problem is not solved it will not be possible to answer a semantic search query across the open Web for a question such as "find all software products that work with Linux and are open-source and are endorsed by people or companies I trust." Why not? Because while there could be tons of raw RDF and OWL instance data out on the Web that is relevant from various ontologies, unless it either all uses the same ontology or all the ontologies that various instances refer to are integrated, the query agent will have no way of making sense of or normalizing the results. Of course, the query agent could simply run the query on all data from all ontologies it knows about, and then just present the results in a single list, sorted by ontology -- but as we've seen above, different ontologies might mean different things by classes with the same names -- and thus the results returned may not really be relevant or well-ordered."
"I believe the solution will ultimately stem from a solution to the Upper Ontology Problem -- if we can solve that problem, then much of the Ontology Integration Problem will go away as most ontologies will automatically be inter-mapped at the Upper-Ontology Level at least. If we had a standard Upper Ontology and furthermore, if this standard were to include concepts for mapping between ontologies and expressing shades semantic mapping and structure between ontological definitions, then mapping would be even easier."