● Type: Select the subtype cluster type, Complete or Incomplete.
• Complete: A subtype cluster is complete when all possible subtype entities are included in the subtype cluster. An example of a complete subtype cluster is one in which Person is the supertype and Male and Female are the subtypes.
• Incomplete: Select if all possible subtype entities will not included be in the cluster. For example, a subtype cluster is made up of several entities, Employee, StoreManager, SalesPerson and StockPerson, each of which stores information about employees. In this example, Employee is the supertype and the remaining entities can be grouped in a subtype. This is probably an incomplete subtype cluster because other employee types cannot be represented in the cluster, such as security guards and cashiers.
● Membership Type: Select Inclusive or Exclusive subtype.
• Inclusive: Select if each supertype that has subtypes can be more than one subtype at a time. For example, an EMPLOYEE and be both an ENGINEER and a WRITER.
• Exclusive: Select if each supertype that has subtypes can be only one subtype at a time. For example, a PERSON cannot be both an EMPLOYEE and a CUSTOMER.
In IE notation, an exclusive subtype is represented with an exclusive OR symbol. The diagram and reports will show the type of supertype/subtype cluster in the TYPE field depending on what you selected, Complete, Inclusive; Complete, Exclusive; Incomplete, Inclusive; Incomplete, Exclusive.
● Discriminator: Select a discriminator from the list.A discriminator is an attribute that distinguishes each of the subtype entities from one another. A subtype discriminator can be a primary key or non-key attribute of the supertype. After you define a discriminator, ER/Studio DA displays it next to its subtype cluster symbol.