Question

Which type of entity has its relationship to another entity determined by an attribute in that other entity called a discriminator?

(a) Subtype entity
(b) Archetype entity
(c) Instance entity
(d) Supertype entity

Answer 1

A subtype entity's relationship to another entity is determined by a discriminator attribute in that other entity, which is necessary in database design for classifying entities under a general category into more specific subgroups.

Step-by-step explanation:

The type of entity described in the question is a subtype entity. In database design, particularly in the entity-relationship model, a subtype entity is determined by an attribute in another entity, which is known as a discriminator. A discriminator is an attribute that determines the subtype of an entity based on its value. The concept can be understood by considering an entity called 'Vehicle' and its subtypes 'Car' and 'Truck'. The discriminator attribute, such as 'VehicleType', will determine the specific subtype.

The supertype entity in this relationship typically holds the common attributes, while each subtype entity holds attributes unique to that type. This modeling technique allows a single database table to more efficiently store multiple kinds of entities while still maintaining clean separation in the dataset. For instance, the 'Car' subtype could have attributes unique to cars, such as 'number of doors', while 'Truck' could have attributes like 'cargo capacity'.