Craig A. Knoblock and Alon Y. Levy
Information agents answer user queries using a large number of diverse information sources. The key issue in their perfomance is finding the set of information sources relevant to a query. Previous work has considered determining relevance soley based on compile-time analysis of the query. We argue that at compile-time, it is often not possible to significantly prune the set of sources relevant to a query, and that run-time information is needed. We make the following contributions. First, we identify the different types of information that can be obtained at run-time, and how they can be used to prune information sources. Second, we describe an algorithm which naturally extends query planning algorithms to exploit run-time information. Third, we describe the discrimination matrix, which is a data structure that identifies the information that can be used to help discriminate between different possible sources.