Help:Adding External Ontologies

Reusing Ontology in Semantic Media Wiki

The way in which Semantic MediaWiki represents knowledge was partially inspired by Web Ontology Language(OWL DL) and one can naturally relate the elements of the wiki, i.e. the individual content pages, to the basic vocabulary of OWL. Complex features of OWL are not used in Semantic MediaWiki and it make use of some characteristic OWL features such as equality reasoning and transitive roles. Dividing OWL DL ontological elements into instances that represent individual elements of the described domain, classes that represent sets of individuals, and roles which represent binary relations between individuals. Semantic MediaWiki can naturally relate the elements of the wiki to the basic vocabulary of OWL, i.e.:

• OWL individuals are represented by normal article pages which usually belongs to Main namespace. But several additional namespaces, such as Image or User, also could be interpreted as individuals.
• OWL classes in turn have counterparts in the wiki in form of MediaWiki categories in the Category namespace. These can be organized in a hierarchical, so one category could contain other categories.
• OWL properties, (roles in description logic), do not have a natural counterpart in MediaWiki, and were introduced by the Semantic MediaWiki extension. The object-properties (describing relationships between two individuals from OWL DL) from data-properties (associating individuals with values of a given datatype). Both are represented by pages in Property namespace in Semantic MediaWiki (properties and attributes are unified now in SMW).

The export function that generates OWL/RDF documents associates URIs with all wiki pages. This very simple schema information allows also the main functionality of wiki, that is mainly used to provide concrete descriptions of individuals and their relationship (ABox in description logics). Employing an OWL external ontology in combination with OWL wiki content depends on the type of entity that one considers, this is achieved with owl:sameAs, owl:equivalentClass, and owl:equivalentProperty. Usually the only problem in doing so is the mapping between elements of the two ontologies. OWL provides us with expressive means to describe that two different URIs represent the same entity (with respect to its extensional inter- pretation).

owl:sameAs URI             URI (on article pages)
owl:equivalentClass URI    URI (on category pages)
owl:equivalentProperty URI URI (on relation/attribute pages)