BCS 260 Lecture Notes - Lecture 4: Peter Chen, Expose
Document Summary
When you create a database, data requirements must first be documented in a data model. A number of techniques can be used to create data models: the most popular is the entity-relationship model created by peter. For example: physical things (reports, parts, people), events (meetings) Know the principle components of the e-r model. An entity is something that users want to track. Entity refers to the entity set and not to a single entity occurrence. Entities of a given type are grouped into an entity class such as. Employee (a collection of all employee entities) which are shown in all caps. An entity instance of an entity class is the occurrence of a particular entity, such as. Expose ambiguities: at times, different people in the organization have different understanding of the data and how data items relate to each other.
