A visual query language for an ER data model

A graphical representation of an ER (entity-relationship) data model and its application to interactive visual query languages are presented. A method for implementing an ER query interface for a relational database management system is outlined. The approach is based on graphical representation and interactive manipulation of ER database schemas. During the process of query formulation the information needed to generate an equivalent SQL expression for a relational database is accumulated. The sample interactions between the user and system are given. The graphical query formulation process is formally defined. Formal definitions that provide the basis for an efficient visual query language implementation are presented