Quick and incomplete responses: The semantic approach
Chung-Dak Shum · 1993
Conventional query optimization usually minimizes the total time for complete evaluation of a query. We argue that this criterion may not be the only or even necessary requirement. In some interactive environments, a complete answer set may not be required and quick responses to queries can be very desirable. Minimizing the processing time for obtaining a single answer, a few answers, or most answers are identified as other potential optimization objectives. We attempt these optimization problems by adopting a strategy that first looks at places where answers are most concentrated. We are implementing a system (QAns) which provides quick answers to the user. The design of QAns is a loosely couple of a query transformer to a conventional query optimizer. The idea is based on semantic query optimization. However, we introduce an additional logical equivalence in the query transformation process. We target the transformations towards reducing the cost of the set of more expensive operatio...