Exam 5: Advanced Data Modeling

Disjoint subtypes are subtypes that contain nonunique subsets of the supertype entity set.

In specialization hierarchies with multiple levels of supertype and subtypes,a lower-level subtype can inherit only a few of the attributes and relationships from its upper-level supertypes.

Disjoint subtypes are also known as subtypes.

The is the result of adding more semantic constructs to the original entity relationship (ER)model.

The relationships depicted within the specialization hierarchy are sometimes described in terms of "is­a" relationships.

If one exists,a data modeler uses a as the primary key of the entity being modeled.

The property of enables an entity subtype to inherit the attributes and relationships of the supertype.

Overlapping subtypes are subtypes that contain a unique subset of the supertype entity set.

A total completeness constraint is represented by .

Nonoverlapping subtypes are subtypes that contain a(n)subset of the supertype entity set.

An entity cluster is a "virtual" entity type used to represent multiple entities and relationships in the ERD.

The completeness constraint can be partial or total.

A is a primary key created by a database designer to simplify the identification of entity instances.

The entity supertype contains common characteristics,and the entity subtypes each contain their own unique characteristics.

At the implementation level,the supertype and its subtype(s)depicted in the specialization hierarchy maintain a 1:1 relationship.

Generalization is based on grouping unique characteristics and relationships of the subtypes.

The specifies whether each entity supertype occurrence must also be a member of at least one subtype.

Surrogate primary keys are especially helpful when there is no key.

The default comparison condition for the subtype discriminator attribute is the comparison.

keys work with primary keys to properly implement relationships in the relational model.