A conceptual level database language for the entity relationship (ER) modelimplicitly contains integrities basic to ER concepts and special retrieval seman-tics for inheritances of attributes and relationships. Prolog...A conceptual level database language for the entity relationship (ER) modelimplicitly contains integrities basic to ER concepts and special retrieval seman-tics for inheritances of attributes and relationships. Prolog, which belongs tothe logical and physical level, cannot be used as a foundation to directly definethe database language. It is shown how Prolog can be enhanced to under-stand the concepts of entities, relationships, attributes and is-a relationships.The enhanced Prolog is then used as a foundation to define the semantics of adatabase query language for the ER model. The three basic functions of modelspecification, updates and retrievas are defined.展开更多
文摘A conceptual level database language for the entity relationship (ER) modelimplicitly contains integrities basic to ER concepts and special retrieval seman-tics for inheritances of attributes and relationships. Prolog, which belongs tothe logical and physical level, cannot be used as a foundation to directly definethe database language. It is shown how Prolog can be enhanced to under-stand the concepts of entities, relationships, attributes and is-a relationships.The enhanced Prolog is then used as a foundation to define the semantics of adatabase query language for the ER model. The three basic functions of modelspecification, updates and retrievas are defined.
