In some cases, entities can be self-linked.
An entity is an object or concept about which you want to store information. Entities, which are represented by rectangles.Back to topĪn ER diagram has three main components: entities, relationships, and attributes connected by lines. IE notation uses Crow's foot to express cardinality (one to many relationship) instead of Chen's notation to epxress the same. In the 1980s, another computer scientist named James Martin, worked to further refine Chen's ER model and introduced what's known today as the IE notation. Peter Chen's work was greatly influenced by scientists and engineers who came before him, specifically Charles Bachman, who worked on visualizing databases in the 1960s and his data structure diagrams became known as Bachman diagrams.Ĭhen's entity relationship model is in many ways the foundation for later practices like Unified Modeling Language or UML in information systems. With an ERD, Chen could provide a unified framework for database modeling. Prior to ERDs, there were three data models for databases: the network model, the relational model, and the entity set model.Įach had their own strengths and weaknesses, but none provided a complete view of the database. His entity relationship model was a way to visualize a database that unified other existing models into a single understanding that removed ambiguities. Peter Chen was a computer scientist who worked on improving database design.
Peter Chen developed ERDs in the 1970s and published his proposal for entity relationship modeling in a 1976 paper titled "The Entity-Relationship Model: Toward a Unified View of Data". The History of Entity Relationship Diagrams
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