An implementation of a QUEL language interface to a database management system



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QUEL (QUEry Language) is an English-like data retrieval and manipulation language based on tuple relational calculus. Because of its "nonprocedural" features, users need to specify only "what" is to be accomplished rather than "how" a desired result should be obtained. Therefore, QUEL can be easily learned by users of all levels of experience. In this thesis, QUEL compiler, query optimizer, and query interpreter are implemented. The compiler is capable of detecting syntactic and semantic errors in a query. The optimizer performs the optimization so that a query can be processed in a more efficient way. The interpreter generates a series of operation calls that lead to the result of a query. Also implemented are the user friendly interface facilities which allow users to create, edit, execute, delete a query at a time. The database languages, the QUEL language of INGRES (INteractive Graphics and REtrieval System), and the implementation of the subset of QUEL language on VAX/11 system are discussed.



Database management