On the Relationship of Ontologies and Models

As models and ontologies assume an increasingly central role in enterprise systems engineering the question of how they compare and can be used together assumes growing importance. On the one hand, the semantic web community is starting to propose a central role for “ontologies” in software engineering, while on the other hand the software engineering community has over the last few years been enthusiastically embracing “models” as the core artefact in software development. Superficially, however, ontologies and models are very similar, and in fact are sometimes visualized using the same language (e.g. UML). This has given rise to a variety of different interpretations of the roles of the two technologies, and had generated a certain degree of confusion about the relationship between them. So what exactly is the difference between ontologies and models and why are both concepts needed? Are they basically the same thing viewed from different angles or is there some fundamental difference between them beyond the idiosyncrasies of current tools and languages? This paper discusses this question. After considering common informal distinctions between ontologies and models, and analyzing their fundamental definitions, we propose how they might usefully be distinguished in the future.