A graphical query language for semantic data models

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.