Abstract: A method and apparatus for optimizing a query involving aggregation. Aggregation predicates are represented by a constraint language through which relationships involving aggregation predicates can be shown. As a result, new predicates can be inferred from an initial set of aggregation predicates and optimization techniques which involve inferring new predicates can be applied. It is also shown how to restrict the inferences involving aggregation predicates to only those predicates which will lead to new predicates which are relevant to query optimization. In general, the technique is not limited to query optimization, but may be applied to various applications involving the manipulation of aggregation predicates.

Abstract: A system and method for accepting and responding to queries based on information stored on multiple heterogenous information sources. A uniform query interface to large collections of structured information sources is provided to a user to pose queries using a uniform schema of the available information. A query plan for answering the query is formulated from descriptions of the contents and capabilities of the available information sources. Based on these descriptions logical solutions which are subsets of the complete solution to the query are derived. An order for executing these solutions is determined based on the input requirements and other capabilities of the relevant information sources.

Abstract: Techniques for optimizing queries in a system in which executing the query requires retrieval of information from a number of different data bases which are accessible via a network. In the techniques, a query results in a query plan which includes subplans for querying the data bases which contain the required information. When a subplan is executed in one of the data bases, the data base returns not only the information which results from the execution of the subplan, but also source and constraint information about the data in the data base. The source and constraint information is then used to optimize the query plan by pruning redundant subplans. An embodiment is disclosed in which queries are made to a domain model implemented using a knowledge base system. The domain model includes a world view of the data, a set of descriptions of the data bases, and a set of descriptions of how to access the data. The information in the domain model is used to formulate the query plan.