chapter 5 questions

____ is a generic entity type that is related to one or more entity subtypes.

An entity supertype

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

False

Entity subtypes do not inherit the relationships in which the supertype entity participates

False

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

False

Implementing non-overlapping subtypes requires the use of one discriminator attribute for each subtype

False

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

False

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

False

The relationships depicted within the specialization hierarchy are sometimes described in terms of is-a relationships

False

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

False

Within an specialization hierarchy, a supertype can exist only within the context of a subtype.

False

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

Foreign

____ is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity subtypes.

Generalization

Composite primary keys are particularly useful as identifiers of composite entities, where each primary key combination is allowed only once in the ____ relationship.

M:N

The preferred placement for a foreign key when working with a 1:1 relationship is ____.

Place a foreign key in one of the entities

____ relationships occur when there are multiple relationship paths between related entities.

Redundant

____ data refer to data whose values change over time and for which you must keep a history of the data changes.

Time-variant

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

True

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

True

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

True

One important inheritance characteristic is that all entity subtypes inherit their primary key attribute from their supertype.

True

The completeness constraint can be partial or total.

True

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

a single abstract entity object

In the specialization hierarchy there is a ____ relationship between a subtype and supertype.

b. 1:1

The extended entity relationship model (EERM) is sometimes referred to as the ____.

enhanced entity relationship model

The primary key's main function is to uniquely identify a(n) ____ within a table

entity instance or row

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

equality

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

extended entity relationship model (EERM) extended entity relationship model

In specialization hierarchies with multiple levels of supertype/subtypes, a lower-level supertype inherits all of the attributes and relationships from all of its upper-level subtype.

false

A ____ occurs when you have one entity in two 1:M relationships to other entities, thus producing an association among the other entities that is not expressed in the model.

fan trap

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

inheritance

A specialization hierarchy can have ____ level(s) of supertype/subtype relationships.

many

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

natural

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

natural

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

natural identifier

The "____" characteristic of a primary key states that: The PK should not have embedded semantic meaning. An attribute with embedded semantic meaning is probably better used as a descriptive characteristic of the entity rather than as an identifier.

nonintelligent

Every subtype can have ____ supertype(s) to which it is directly related.

only one

One important inheritance characteristic is that all entity subtypes inherit their ____ key attribute from their supertype.

primary

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

primary

According to the data modeling checklist, ____ should clearly define participation and cardinality rules.

relationships

The "____" characteristic of a primary key states that: The selected primary key must not be composed of any attribute(s) that might be considered a security risk or violation. For example, using a Social Security number as a PK in an EMPLOYEE table is not a good idea

security complaint

The ____ depicts the arrangement of higher-level entity supertypes (parent entities) and lower-level entity subtypes (child entities).

specialization hierarchy

The relationships depicted within the ____ are sometimes described in terms of "is-a" relationships.

specialization hierarchy

A(n) ____ is the attribute in the supertype entity that determines to which entity subtype each supertype occurrence is related.

subtype discriminator

Overlapping subtypes are subtypes that contain ____ subsets of the supertype entity set.

subtypes

An entity supertype can have disjoint or overlapping entity subtypes.

true

Entity supertypes and subtypes are organized in a specialization hierarchy.

true

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

true

Specialization is the top-down process of identifying lower-level, more specific entity subtypes from a higher-level entity supertype.

true

The entity supertype contains the common characteristics and the entity subtypes contain the unique characteristics of each entity subtype.

true

Non-overlapping subtypes are subtypes that contain a(n) ____ subset of the supertype entity set.

unique

The "____" characteristic of a primary key states that: The PK must uniquely identify each entity instance. A primary key must be able to guarantee unique values. It cannot contain nulls.

unique values