SRI: Exploiting Semantic Information for Effective Query Routing in a PDMS

The huge amount of data available from Internet information sources has focused much attention on the sharing of distributed information through Peer Data Management Systems (PDMSs). In a PDMS, peers have a schema on their local data, and they are related each other through semantic mappings that can be defined between their own schemas. Querying a PDMS means either flooding the network with messages to all peers or take advantage of a routing mechanism to reformulate a query only on the best peers selected according to some given criteria. As reformulations may lead to semantic approximations, we deem that such approximations can be exploited for locating the semantically best directions to forward a query to. In this paper, we propose a distributed index mechanism where each peer is provided with a Semantic Routing Index (SRI) for routing queries effectively. A fuzzy-oriented model for SRI is presented where operations for creating and maintaining SRIs are well-founded. In addition, we show how SRIs can be employed in the query processing phase with the aim of reducing the space of reformulations. Finally, we conduct a series of meaningful experiments showing the effectiveness of the proposed approach.