Extended Entity-relationship Model Research Articles

A graphical data manipulation language for an extended entity-relationship model

A user can formulate database queries and updates graphically, by manipulating schema diagrams. The authors based the graphical data manipulation interface on the entity-relationship (ER) model because of its widespread use and increasing popularity. They use an extended ER model incorporating various forms of generalization and specialization, including subset, union and partition relationships. They call their model the extended conceptual entity-relationship or ECER model. A comparison with other graphical entity-relationship interfaces is included. >

A logical design methodology for relational databases using the extended entity-relationship model

A database design methodology is defined for the design of large relational databases. First, the data requirements are conceptualized using an extended entity-relationship model, with the extensions being additional semantics such as ternary relationships, optional relationships, and the generalization abstraction. The extended entity-relationship model is then decomposed according to a set of basic entity-relationship constructs, and these are transformed into candidate relations. A set of basic transformations has been developed for the three types of relations: entity relations, extended entity relations, and relationship relations. Candidate relations are further analyzed and modified to attain the highest degree of normalization desired. The methodology produces database designs that are not only accurate representations of reality, but flexible enough to accommodate future processing requirements. It also reduces the number of data dependencies that must be analyzed, using the extended ER model conceptualization, and maintains data integrity through normalization. This approach can be implemented manually or in a simple software package as long as a "good" solution is acceptable and absolute optimality is not required.