The Entity Relationship Diagram.
The Entity Relationship Diagram (ERD) depicts a conceptual data model that incorporates some of the important scientific information about the real world. It adopts a natural view that the real world consists of entities and relations (Chen, 1976). One objective of the ERD is to create a simple, easy to understand and conveniently presented data model consisting of entities, attributes, relationships and cardinalities. The model serves as tool for database design, where the model can facilitate communication between the system analyst or designer and the end-user during the requirement analysis and conceptual design phases.
Chen published one of the first articles on the entity-relationship model in 1976 at a database conference (Chen, 1976). The concept of entity-relationship already existed for years in the field of philosophy and began to be applied to database design heavily between 1975 and 1980. In 1979, there was a conference on the entity-relationship model during the First International Conference on Entity-Relationship Approach in Los Angeles, California. Annual conferences on the topic continued until 1995, when the conference was renamed the International Conference on Conceptual Modeling (AICCM, 2003). The entity-relationship model is the result of the unification of the hierarchical, network and relational models for developing a logical database design. One important purpose of the entity-relationship model was to have a database model that was independent of the existing database management systems.
An entity is defined as a person, place or thing in the real world or is conceptual, only existing in someone 's mind. An entity that is specific is similar to an object instantiation of a class. Entity types are a more powerful and concise representation of entities. An entity type is a collection of entities that share a common definition. For example, an entity may be a Ford car, whereas an entity type could be a manufacturer. An attribute is any
Chen published one of the first articles on the entity-relationship model in 1976 at a database conference (Chen, 1976). The concept of entity-relationship already existed for years in the field of philosophy and began to be applied to database design heavily between 1975 and 1980. In 1979, there was a conference on the entity-relationship model during the First International Conference on Entity-Relationship Approach in Los Angeles, California. Annual conferences on the topic continued until 1995, when the conference was renamed the International Conference on Conceptual Modeling (AICCM, 2003). The entity-relationship model is the result of the unification of the hierarchical, network and relational models for developing a logical database design. One important purpose of the entity-relationship model was to have a database model that was independent of the existing database management systems.
An entity is defined as a person, place or thing in the real world or is conceptual, only existing in someone 's mind. An entity that is specific is similar to an object instantiation of a class. Entity types are a more powerful and concise representation of entities. An entity type is a collection of entities that share a common definition. For example, an entity may be a Ford car, whereas an entity type could be a manufacturer. An attribute is any
References: AICCM (2003). Anthology of International Conference on Conceptual Modeling. Available http://www.informatik.uni-trier.de/~ley/db/conf/er/. Updated June 6, 2003. Accessed June 9, 2003. Chen, P. P. (1976). The Entity Relational Model - Towards a Unified View of Data. ACM Transactions on Database Systems. Vol 1, No 1. Elmasri, R., Navathe, S. B. (1994a). Fundamentals of Database Systems. Benjamin-Cummings Publication Company. Liu, C.T, Chrysanthis, P.K., Chang, S.K. (1994b). Database Schema Evolution Through the Specification and Maintenance Changes on Entities and Relationships. International Conference on Entity Relationship Approach. Pressman, R.S. (2001). Software Engineering A Practitioner 's Approach. McGraw-Hill. Rumbaugh, J., Blaha, M., Premerlani, W., Eddy, F., Lorenson, W. (1991) Object-Oriented Modeling and Design. Prentice Hall Intl. SD (2003). How To Draw Entity Relationship Diagrams. Available http://www.smartdraw.com/ resources/center/software/erd.htm. Updated June 5, 2003. Accessed June 8, 2003. Si-Said Cherfi, S., Akoka, J., Comyn-Wattiau, I. (2002). Conceptual Modeling Quality - From EER to UML Schemas Evaluation. International Conference on Conceptual Modeling.