Abstract
In this paper, we show how the web ontology language OWL can be accommodated within the larger framework of the heterogeneous common algebraic specification language HETCASL. Through this change in perspective, OWL can benefit from various useful HETCASL features concerning structuring, modularity, and heterogeneity. This tackles a major problem area in ontology engineering: re-use of ontologies and re-combination of ontological modules. We discuss in particular: (1) the extension of the Manchester syntax for OWL with structuring mechanisms of CASL, allowing for explicit modularisation; (2) automatic translations between ontology languages to support ontology design across different ontology languages (heterogeneity); (3) heterogeneous ontology refinements, and corresponding automated reasoning support for different logics.