INFS1603 Lecture Notes - Lecture 3: Chen Model, Foreign Key, Candidate Key

• School: UNSW, UNSW Sydney
• Department: Information Systems
• Course: INFS1603
• Professor: All

Document Summary

The entity relations hip model (erm: an er model is a detailed, logical representation of the data for an organisation or for a business area. In this course, we will use the chen model. Entity: an object about which the system is required to hold data. Entity type (entity class): is a collection of entities that share common properties or characteristics. It is represented as a rectangular box in the er model diagram with the name of the entity inside. Entity instance: is a single occurrence of an entity type. The erm refers to table rows as an entity instance or entity occurrence. Attribute: a property or characteristics of an entity that is of interest to the organisation. Each entity type has a set of general attributes associated with it. Each entity instance has specific values of the attribute associated with it. In an erm, the columns are the attributes.