Integration of heterogeneous information in the context of Internet becomes a key activity to enable a more organized and semantically meaningful access to data sources. As Internet can be viewed as a data-sharing network where sites are data sources, the challenge is twofold. Firstly, sources present information according to their particular view of the matter, i.e. each of them assumes a specific ontology. Then, data sources are usually isolated, i.e. they do not share any topological information concerning the content or the structure of other sources. The classical approach to solve these issues is provided by mediator systems which aim at creating a unified virtual view of the underlying data sources in order to hide the heterogeneity of data and give users a transparent access to the integrated information. In this paper we propose to use a multi-agent architecture to build and manage a mediators network. While a single peer (i.e. a mediator agent) independently carries out data integration activities, it exchanges knowledge with other peers by means of specialized agents (i.e. brokers) which provide a coherent access plan to access information in the peer network. This defines two layers in the system: at local level, peers maintain an integrated view of local sources, while at network level agents maintain mappings among the different peers. The result is the definition of a new networked mediator system intended to operate in web economies, which we realized in the SEWASIE (SEmantic Webs and AgentS in Integrated Economies) project. SEWASIE is a RDT project supported by the 5th Framework IST program of the European Community successfully ended on September 2005.

distributed databases, distributed applications, query language, internet, ontologies, mediator, knowledge management