The Distributed Ontology Language (DOL) is a standardisation of a meta-language for heterogeneous ontology representation and is currently under development within the ISO standard OntoIOp.

The DOL is not only another ontology language such as OWL, DAML+OL, etc., but it also provides a meta-level framework to express logically heterogeneous and distributed ontologies with precise semantics and proof theory. Furthermore, the framework allows linking between ontologies, annotations, and the documentations of ontologies. The standard specifies syntax, semantics, and conformance criteria.

The ontology structure can be defined in various formalisms. Each of them supports its own features and satisfies the requirements for specific purposes of an ontology. The problem comes when the ontology must be used in another system supporting some other formalisms. DOL allows users to use their own preferred ontology formalism and makes it interoperable with other DOL-conforming ontology formalisms. DOL is the first language to systematically support this.