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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 someones 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 aspect feature quality or characteristic of an entity An attribute must be capable of being defined in terms
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