Knowledge-based query processing in object bases
CSC '86 Proceedings of the 1986 ACM fourteenth annual conference on Computer science
Query Optimization in Database Systems
ACM Computing Surveys (CSUR)
Modelling concepts for reasoning about access to knowledge
Proceedings of the 1980 workshop on Data abstraction, databases and conceptual modeling
Research in knowledge base management systems
ACM SIGMOD Record
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An approach to query optimization is described that draws on two sources of knowledge: real world constraints on the values for the application domain served by the database; and knowledge about the current structure of the database and the cost of available retrieval processes. Real world knowledge is embodied in rules that are much like semantic integrity rules. The approach, called "query rephrasing", is to generate semantic equivalents of user queries that cost less to process than the original queries. The operation of a prototype system based on this approach is discussed in the context of simple queries which restrict a single file. The need for heuristics to limit the generation of equivalent queries is also discussed, and a method using "constraint thresholds" derived from a model of the retrieval process is proposed.