A formal basis for an abbreviated concept-based query language

摘要

Concept-based query languages allow users to specify queries directly against conceptual schemas. The primary goal of their development is ease-of-use and user-friendliness. However, existing concept-based query languages require the end-user to explicitly specify query paths in totality, thereby rendering such systems not as easy to use and user-friendly as they could be. The conceptual query language (CQL) discussed in this paper also allows end-users to specify queries directly against the conceptual schemas of database applications, using concepts and constructs that are native to and exist on the schemas. Unlike other existing concept-based query languages, however, CQL queries are abbreviated, i.e., the entire path of a query does not have to be specified. CQL is, therefore, an abbreviated concept-based query language. CQL is developed with the aim of combining the ease-of-use and user-friendliness of concept-based languages with the power of formal languages. It does not require end-users to be familiar with the structure and organization of the application database, but only with the content. Therefore, it makes minimal demands on end-users' cognitive knowledge of database technology without sacrificing expressive power. In this paper, the formal semantics and the theoretical basis of CQL are presented. It is shown that, while CQL is easy to use and user-friendly, it is nonetheless more than first-order complete. A contribution of this study is the use of the semantic roles played by entities in their associations with other entities to support abbreviated conceptual queries. Although only mentioned here in passing, a prototype of CQL has been implemented as a front-end to a relational database manager.