This paper presents a graphical query language for semantic data models. This language is based on a generic semantic model. It is integrated in the CANDID system, which is a graphical interface fur the manipulation of databases. Any schema is represented by a graph divided into families of object types. The graphical query language makes it possible to express a request by describing with a graph an object solution of the request. A request is sometimes expressed in several stages. A stage corresponds to the expression of a simpler subrequest. This language is also characterized by the absence of boolean operators and quantifiers, which are replaced by manipulations on Venn diagrams. Since a request in fact defines derived elements, almost all of a request can be incorporated into the schema. CANDID has been designed to be adapted to any DBMS which has deduction mechanisms.
Schneider, M. and Trepied, C., "A GRAPHICAL QUERY LANGUAGE FOR SEMANTIC DATA MODELS" (1989). ICIS 1989 Proceedings. 51.