Entity-Relationship modeling

In the previous sections, we briefly defined the three components of an E-R model: entity, attribute, and relationship. We have also seen a few E-R diagrams, drawn with different notations such as UML or crow’s foot.

In this section, we will define in a bit more detail the E-R models and show how different cases can be represented in these two common notations (UML and crow’s foot).

Main notation

We have already introduced the three components of an E-R model. In this section, we explain how they are represented visually in E-R models:

• Entity: This is represented as a box with the name of the entity inside

If attributes are shown, the entity name is at the top and often in bold or bigger and visually separated from the attributes

• Attribute: This is represented by the attribute’s name inside the box of the entity it belongs, with one name per line
• Relationship: This is represented by a line joining...