Web Ontology Language

The W3C's standard for publishing ontologiesontology, n.: A carefully defined vocabulary for a subject such as medicine, spelling out each kind of thing, how kinds nest inside one another, and which connections between them are allowed. on the semantic websemantic web, n.: An effort to label data on the web in a standard, precise way so that programs, not only human readers, can tell what it means and connect facts drawn from many different sites., expressed on top of RDFResource Description Framework, prop. n.: A web standard for writing facts as simple three-part statements — subject, relation, object — using web addresses as names, so that data from different sources can be merged automatically.. It defines classes, properties and individuals and lets authors state class expressions (intersections, unions, complements, property restrictions such as 'has at least one child'), property characteristics (transitive, symmetric, functional, inverse) and equivalence or disjointness. Its main dialect has model-theoretic semantics given by the description logicdescription logic, n.: A family of precise logical languages for defining categories and how they relate, such as 'a parent is a person with at least one child', designed so that a computer's reasoning about them always finishes. SROIQ, so automated reasoners can check consistency and infer class hierarchies; the OWL 2 profiles EL, QL and RL restrict expressiveness to keep reasoning tractable at scale. OWL follows the open-world assumption — missing information is unknown, not false — which often surprises users used to databases and the closed-world assumptionclosed-world assumption, n.: The rule of treating whatever a system cannot confirm as false: if a library's catalog does not list a book, the library is assumed not to have it.. OWL ontologies are commonly edited in Stanford's open-source Protégé tool.