Distributed Query Processing in P2P Systems with Incomplete Schema Information

The peer-to-peer (P2P) paradigm has emerged recently, mainly by file sharing systems like Napster or Gnutella and in terms of scalable distributed data structures. Because of the decentralization P2P systems promise an improved scalability and robustness, and they open a new view on data integration approaches, too. By exploiting already available mappings between pairs of peers a new peer joining the systems can immediately participate and access all the available data after establishing a correspondence mapping to at least one other peer. One of the technical challenges in building scalable P2P based integration systems is the efficient processing of queries which is complicated by the locally restricted knowledge about data placement and schema information. In this paper, we address this problem by investigating query processing strategies dealing with incomplete schemas and present results of our experimental evaluation.