A conceptual level database language for the entity relationship (ER) model implicitly contains integrities basic to ER concepts and special retrieval semantics for inheritances of attributes and relationships. Prolog, which belongs to the logical and physical level, cannot be used as a foundation to directly define the database language. It is shown how Prolog can be enhanced to understand the concepts of entities, relationships, attributes and is-a relationships. The enhanced Prolog is then used as a foundation to define the semantics of a database query language for the ER model. The three basic functions of model specification, updates and retrievals are defined.