Rules & Ontologies OWL 2 RL & SWRL Description Logic ... - LPIS

OWA vs. CWAExamplesUnique-Name Αssumption (UNA)4-5• Example in favor of OWA– Question: “Did it rain in Tokyo yesterday?”– Answer: “I don’t know that it rained, but that’s notenough reason to conclude that it didn’t rain.”• Example in favor of CWA– Question: “Was there a big earthquake disaster inTokyo yesterday?”– Answer: “I don’t know, but if there had been such adisaster, I’d have heard about it. Therefore I concludethat there wasn’t such a disaster.”Rules & OntologiesA Semantic Web Primer, 3rd Edition4-6• When two individuals are known by differentnames, they are in fact different individuals.– Sometimes works well and sometimes not• In favor: when two products in a catalog are knownby different codes, they are different• Against: two people in our social environmentinitially known with different identifiers (e.g., “Prof.van Harmelen” and “Frank”) are sometimes thesame personRules & OntologiesA Semantic Web Primer, 3rd EditionUnique-Name Αssumption (UNA)CWA vs. OWA• OWL does not make the unique-nameassumption• It is possible to explicitly assert of a set ofidentifiers that they are all unique– using owl:allDifferente • Databases and logic-programming systemssupport closed worlds and unique names• Knowledge representation systems andtheorem provers support open worlds andnon-unique names• Ontologies are sometimes in need of oneand sometimes in need of the other.– Big debate in the literature4-7Rules & OntologiesA Semantic Web Primer, 3rd Edition4-8Rules & OntologiesA Semantic Web Primer, 3rd Edition2