Entity instances are associated by relationship classes.

More Questions from Data Modeling with ER Model

• Composite identifiers consist of two or more attributes.
• All instances of an entity class have the same attributes.
• A maximum cardinality is the maximum number of entity instances that can participate in a relationship instance.
• Entities use identifiers while tables use keys.
• 1:1, 1:N and N:M relationships are also known as HAS-A relationships.
• An attribute describes the entity's characteristics.
• The degree of a relationship refers to the number of entity classes in the relationship.
• An identifier determines the type of relationship that an entity has.
• A recursive relationship is a relationship between an archetype and an instance of that archetype.
• A subtype entity is a special case of another entity called a supertype entity.

Discussion & Comments