Extending OWL to Support Custom Relations

Web Ontology Language (OWL) is used by domain experts to encode knowledge. OWL primarily only supports the subClassOf (is-a or inheritance) relation. Various other relations, such as partOf, are essential for representing information in various fields including all engineering disciplines. The current syntax of OWL does not support the declaration and usage of new custom relations. Workarounds to emulate custom relations do exist, but they add syntax burden to knowledge modelers and don't support accurate semantics for inference engines. This paper proposes minimal syntax extension to OWL for declaring custom relations with special attributes, and applying them in knowledge representation. Domain experts can apply custom relations intuitively and concisely as they do with the familiar built-in subClassOf relation. We present our additions to the OWL API for the declaration, application, and visualization of custom relations. We outline our revision and additions to the ontology editor Protégé so its users could visually declare, apply and remove custom relations according to our enriched OWL syntax. Work relating to our modification of the OWLViz plugin for custom relations visualization is also discussed.