Entity Relationship Diagram


Entity Relationship Diagram
Develop an ER model to represent the information requirements in a case study
List all business rules that are apparent from the case study
Record all important assumptions that justify your decisions and actions taken in developing your ER model
Write brief definitions for the entities and attributes in your model.
Entity-relationship data model
You are required to develop an ER model to represent the information requirements for a database system for the state government Health & Security Agency as described on last page.
Your ER model must:
• show all necessary entities, attributes and relationships
• show unique identifiers
• show multi-valued attributes (also called repeating attributes), if any
• show participation and cardinality
• show associative entities, if appropriate
• use the notation described in the set text
• use consistent and appropriate naming for entities and attributes throughout (refer to Chapter 2 & 3 of set text).
Some business rules or other aspects of the case study may not be clear to you when you read the case study. If this is the case, then you should either approach your lecturer or tutor for clarification, or you may simply make an assumption and then develop your ER model accordingly. For example, the case study might not mention all relevant participation information (also called minimum cardinalities). If so, you may make an assumption about what the minimum cardinalities might reasonably be, and then show these in your ER model accordingly. You should justify each assumption in terms of the business, for example: it is assumed that each customer must have at least one order because it is assumed that the business does not record customer details until the customer places an order.
If I were running this business, what things would I need to keep a list of?’ Write those things down. For each thing, what information would you need to record about it?