P2P semantic mediation of web sources

XML Mediators are focused on supporting the XQuery (or sometimes the SQL/XML) query language on XML views of heterogeneous data sources. Wrappers leverage data sources to XML views with basic query capabilities. The data are integrated on demand by the mediator delegating sub-queries to wrappers. Using such information integration platforms to query the semantic web is a challenge both for scalability and data semantic reasons. On another side, semantic Peer-to-peer (P2P) networks are emerging as an important infrastructure to manage distributed data, notably on the web. An important goal concerns improving query facilities of distributed heterogeneous data. Coupling data mediation and P2P technology, P2P data mediation strives to support efficiently advanced queries upon heterogeneous data sources annotated with various metadata and mapping schemes. We analyze the main services provided by mediation systems and discuss their extension to the semantic web in P2P mode. We shortly discuss the annotation service for describing sources syntactically and semantically, the routing service to route data location requests, and the query service to resolve distributed queries. We survey some projects and report on PathFinder, an experimental P2P mediation system developed at University of Versailles in the Context of the Satine European project.