In computer science and artificial intelligence, ontology languages are formal languages used to construct ontologies. They allow the encoding of knowledge about specific domains and often include reasoning rules that support the processing of that knowledge. Ontology languages are usually declarative languages, are almost always generalizations of frame languages, and are commonly based on either first-order logic or on description logic.
Classification of ontology languages
Classification by syntax
Traditional syntax ontology languages
- Common Logic - and its dialects
- DOGMA (Developing Ontology-Grounded Methods and Applications)
- F-Logic (Frame Logic)
- KIF (Knowledge Interchange Format)
- Ontolingua based on KIF
- KM programming language
- LOOM (ontology)
- OCML (Operational Conceptual Modelling Language)
- OKBC (Open Knowledge Base Connectivity)
- PLIB (Parts LIBrary)
Markup ontology languages
- Ontology Inference Layer (OIL)
- Web Ontology Language (OWL)
- Resource Description Framework (RDF)
- RDF Schema (RDFS)
Classification by structure (logic type)
Three languages are completely or partially frame-based languages.
Gellish is an example of a combined ontology language and ontology that is description logic based. It distinguishes between the semantic differences among others of:
- relation types for relations between concepts (classes)
- relation types for relations between individuals
- relation types for relations between individuals and classes
It also contains constructs to express queries and communicative intent.
Several ontology languages support expressions in first-order logic and allow general predicates.