7: Entity Relationship Modelling
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When designing a database it is common practice for a database designer to develop an Entity Relationship model and to represent that model in a drawing, the entity relationship diagram (ERD). In this chapter we discuss the concepts required to develop an ERD and the Peter Chen notation. Peter Chen introduced entity relationship modeling in his paper The Entity-Relationship Model--Toward a Unified View of Data (ACM Transactions on Database Systems, Vol. 1, No. 1, 1976). This paper can be found at csc.lsu.edu/news/erd.pdf; it is one of the most cited papers in the computer field, and has been considered one of the most influential papers in computer science. Another later paper published in Software Pioneers: Contributions to Software Engineering (2002) is Entity-Relationship Modeling: Historical Events, Future Trends, and Lessons Learned and can be found at http://bit.csc.lsu.edu/~chen/pdf/Chen_Pioneers.pdf.
Entity Relationship modeling is a process used to help us understand and document the informational requirements of a system as a logical or conceptual data model. When the model is complete we then create a physical model in some database management system (DBMS); typically a relational DBMS, or RDBMS.