Generating Complete Query Plans given Approximate Descriptions of Content Providers

Information brokers can use information available from content providers to answer complex user queries. To accomplish this task they need descriptions of the domains of content providers. Domains can often be described only approximately by giving lower and upper bounds on the data available, because exact descriptions might be too complex and ineecient to deal with. This paper presents an algorithm to generate query plans for an information broker given only approximate descriptions. The algorithm guarantees completeness, meaning that all information available from content providers and requested by the user will be retrieved. Furthermore, the algorithm selects the minimum number of content providers which guarantees completeness given only approximate descriptions.