The answerability of database queries

摘要

A conceptual model is presented of the man-machine interface in data-base environments. It is suggested that this model, entitled Query Normal Form (QNF), is a universal mediator between formal query languages and relationally structurable data bases. As such, it provides a high degree of independence of query formulation from specific data-base structures. Furthermore, it can be used to verify the syntactic and semantic validity of queries stated in formal query languages before the initiation of data-base search.The descriptive adequacy of QNF as a model of formal query languages is established, as is its relational completeness in data-base interrogation capabilities. Finally, possible errors in QNF, both syntactic and semantic, are evaluated, and this line of research is compared with that of natural language query systems.