This invention provides methods to locate and plan the retrieval of data from networked information sources in response to a user query. The methods utilize descriptions of the information sources, the information domain of the sources, and of the query. The methods of this invention integrate both legacy systems and full relational databases with an efficient, domain-independent, query-planning algorithm, reason about the capabilities of different information sources, handle partial goal satisfaction i.e., gather as much data as possible when all that the user requested cannot be gathered, are both sound and complete, and are efficient.