Schema Mediation and Query Processing in Peer

P2P Data Management Systems (PDMSs) allow the efficient sharing of data between peers with overlapping sources of information. These sources share data through semantic mappings between peers. In current systems, queries are asked over each peer’s local schema and then translated using the semantic mappings between peers. In this thesis we propose that a mediated schema can benefit PDMSs by allowing access to more data and by making that access comprehensible. We present our system MePSys, which uses the mediated schema as a media for query translation in relational PDMSs. We show how to create a mediated schema in PDMSs automatically using the semantics of the existing mappings provided to translate queries. We further discuss how to update the mediated schema in a stable state, i.e., after the system setup period.