QBD: a fully visual system for E-R oriented databases

The need of a friendly man-machine interaction is becoming crucial for a large variety of applications, in particular, those requiring frequent extraction of information from the database. Experience suggests that traditional query languages are not friendly enough for the casual user: she/he is requested to formulate queries in a textual language, without any iconic or spatial clues to help the querying process. A new generation of languages (visual languages) has been recently investigated, that attempts to make extensive use of the person´s instincts and senses. The authors propose a fully visual system, called Query by Diagram (QBD), which is based on a conceptual data model, a query language defined on this model and a graphical user interface. The main characteristics of the interface are the ease of use, and the availability of a rich set of primitives for both schema selection and query formulation. Unlike many present proposals of graphical query systems, graphical operations are formally defined from both a syntactic and a semantic point of view