Linking the Semantic Web with existing sources

The Semantic Web aims at providing Web data sources on a semantic level. On the other hand, most of the Web data itself is not suitably prepared (e.g., by annotations). In this paper, we describe a semantic layer that integrates existing data sources with the Semantic Web by combining semantic modeling with links that associate the semantic notions with actual data on the Web. The semantic level consists of specialized service providers - which can be seen as agents - for each application domain. Each agent contains ontological knowledge represented in XML where the links to the actual data are embedded as XPath expressions, similar to XLink. The agent uses its knowledge with an internal reasoning mechanism to combine the links for translating a Semantic Web query into a Web query that is then evaluated against the individual sources.