The Semantic Web (SW) is a proposed extension to the current Web. It aims at providing a ubiquitous medium for information exchange not only among human beings but also among software agents. The development of Semantic Web takes a layered approach. RDF is the cornerstone ontology language. It describes Web resources using binary relations. RDF Schema provides basic vocabulary for RDF documents. DAML+OIL and later web ontology languages are based on description logics and RDF Schema, tapping the synergy from AI and Web communities. It has a richer set of language constructs to describe knowledge hierarchy and the relationships between various concepts. The Web Ontology Language (OWL) is based on DAML+OIL and is now a W3C recommendation. The current W3C’s Semantic Web effort is focusedon developing logical rules languages and SWRL FOL, an extension to SWRL, is the latest proposal. It attempts to address the expressivity issue of OWL and SWRL by incorporating concepts in first-order logic.
We started a joined project aiming to define an integrating mathematical structure underlying all these languages. Our approach uses the institution theory to define this structure. Institutions were introducedby J. Goguen and R. Burstall to formalize the notion of logical system andto provide a basis for reasoning about software specifications independentof the choice of the underlying logical system. We show that the logics underlying SW languages can be organized as intstitutions. We investigate the properties of these institutions, the relationships between them, and their relationship with other formalisms.The talk starts with a brief introduction in the institution theory, and then presents a brief introduction in SW languages by means of institution theory.