Merging sub-ontologies

Ontologies, such as UMLS and WordNet, are generally very large, and are normally the source of more specialised and smaller ontologies tailored for a certain application. It is natural that the source ontologies be multiple large ontologies, each of which is extracted, and then merged to create a smaller and tailored ontology for a specific domain. Therefore, extracting subontologies as well as merging them is a primary process. In this paper, we propose sub-ontology extraction and merging, whereby multiple sub-ontologies are extracted from various source ontologies and then these extracted subontologies are merged to form a complete ontology to be used by the user. We use the maximum extraction method to facilitate this. A walkthrough case study using the UMLS meta-thesaurus ontology is also presented.