Exam 5: Advanced Data Modeling

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

Within a specialization hierarchy, every subtype can have supertype(s) to which it is directly related.

In the context of total completeness, in a(n) , every supertype occurrence is a member of only one subtype.

Some designs use redundant relationships as a way to simplify the design.

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.

An entity supertype can have disjoint or overlapping entity subtypes.

An entity cluster is formed by combining multiple interrelated entities into .

The most important characteristic of an entity is its key, used to uniquely identify each entity instance.

To model time-variant data, one must create a new entity in an M:N relationship with the original entity.

Which of the following is a specialization hierarchy overlapping constraint scenario in case of partial completeness?

The function of the primary key is to describe an entity.

The purpose of a(n) is to simplify an entity-relationship diagram (ERD) and thus enhance its readability.

Explain the "no change over time" characteristic of a primary key.

A design trap occurs when a relationship is improperly or incompletely identified and is therefore represented in a way that is not consistent with the real world.

A subtype contains attributes that are common to all of its supertypes.

completeness means that not every supertype occurrence is a member of a subtype.

Composite keys are useful as identifiers of weak entities, where the weak entity has a strong relationship with the parent entity.

A key is a real-world, generally accepted identifier used to uniquely identify real-world objects.

A total completeness constraint is represented by .

When selecting a foreign key placement for a 1:1 relationship, place the PK of the entity on the mandatory side in the entity on the optional side as a FK, and make the FK mandatory when .