Dynamic Query Processing in DIOM

In an open environment such as the Internet, query responsiveness involves both the capability of responding to a query within a reasonable time frame and the capability of dynamically incorporating the new information sources and the up to date information of existing data sources into the answer of a query. In this paper we present the dynamic distributed query processing framework, developed in the DIOM project, to demonstrate the feasibility and the bene t of improving responsiveness of querying across heterogeneous information sources, without relying on an integrated global view schema pre-de ned over all the participating information sources. Then we discuss several issues with respect to improving query responsiveness in the context of DIOM, including how the information consumers' queries are dynamically processed and linked to the relevant information sources, and how the query scheduling framework scales up in an environment where information sources accessible to users are constantly and rapidly changing, in their content, numbers, identity, and connectivity.