Relationships › Additional Relationship Types › Inclusive and Exclusive Relationships

Inclusive and Exclusive Relationships

Unlike IDEF1X, IE notation does not distinguish between complete and incomplete subtype relationships. Instead, IE notation documents whether the relationship is exclusive or inclusive. However, IDEF1X notation distinguishes between complete and incomplete; exclusive and inclusive.

In an exclusive subtype relationship, each instance in the supertype can relate to one and only one subtype. For example, you might model a business rule that says an employee can be either a full-time or part-time employee but not both. To create the model, you can include an EMPLOYEE supertype entity with FULL‑TIME and PART-TIME subtype entities and a discriminator attribute called “employee-status.” In addition, you can constrain the value of the discriminator to show that valid values for it include F to denote full-time and P to denote part-time.

In an inclusive subtype relationship, each instance in the supertype can relate to one or more subtypes. In our example, the business rule might now state that an employee could be full-time, part-time, or both. In this example, you can constrain the value of the discriminator to show that valid values for it include F to denote full-time, P to denote part-time, and B to denote both full-time and part-time.

Note: In IDEF1X notation, you can represent inclusive subtypes by drawing a separate relationship between the supertype entity and each subtype entity.