Preferences; Putting More Knowledge into Queries 论文

摘要

Classical query languages provide a way to express mandatory qualifications on the data to be retrieved. They do not feature facilities for expressing preferences or desirable qualifications. The need for preferences is illustrated in a software engineering framework. A preference mechanism is then presented as an extension of a language of the Domain Relational Calculus family, and the expressive power of the resulting language is discussed. The proposed mechanisms are shown to effectively allow the use of queries for supporting software configuration management functions.