Describe the types of entity-relationship diagrams.
Types of Entity-relationship Diagrams
The three best-known types of ER diagrams are:
The Crowsfoot model','One of several types of entity-relationship (ER) diagrams, the Crowsfoot model neatly packages entities with their attributes by placing them in boxes. Also referred to as the Information Engineering model. Crowsfoot model (also called the Information Engineering model)
The Chen model','One of several types of entity-relationship ER-diagrams. The Chen model is named after the inventor of ER diagramming Chen model.
The IDEF1X model (the least well-known of the three)
To get a sense of how different (but also, of how similar) these three models are, consider the following business rule, captured by each type of diagram: "An office is assigned to employees." (Do not be concerned at this point with interpreting the diagrams--you'll learn how to do that shortly.)
There is no "standard" ER diagram. Many others, besides these three, are in use.
Fortunately, once you have learned to interpret one of them, it’s fairly easy to learn how to read any of the others.
In this module, you will work exclusively with the Crowsfoot model.
The next lesson illustrates the conventions used to diagram entities and attributes with the Crowsfoot model.
Before moving on to the next lesson, click the link below to see if you can identify the three best-known types of ER diagrams.