QBD STAR - A GRAPHICAL QUERY LANGUAGE WITH RECURSION

One of the main problems in the database area is to define query languages characterized by both high expressive power and ease of use. In this paper, we propose a system to query databases, using diagrams as a standard user interface. The system, called Query by Diagram* (QBD*), makes use of a conceptual data model, a query language on this model, and a graphical user interface. The conceptual model is the Entity-Relationship Model; the query language, whose expressive power allows recursive queries, supports visual interaction. The main characteristics of the interface are ease of use and the availability of a rich set of primitives for schema selection and query formulation. Furthermore, we compare the expressive power of QBD* and G+, which are the only languages allowing recursive queries to be expressed graphically. © 1990 IEEE