In this paper we have outlined some research solutions within the framework of ontology integration that are based on formal upper and core ontologies. Some details have been given on how informal schemata such as thesauri, reference tables, and topic trees can be reused and refined in order to be manipulated by ontology integration. Some hints have also been shown about the dependence of topic trees from ontologies, a promising research area for the semantic web.
In fact, the overall research issue underlying the FOS project is to provide a unified methodology of ontology integration based on formal ontologies, ontology library design, topic trees building and maintainance, and efficient web search and indexing.
