Chapter 5

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

False

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. False True

False

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

False

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

False

The property of a subtype discriminator enables an entity supertype to inherit the attributes and relationships of the subtype. True False

False

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

False

A _____ key is a real-world, generally accepted identifier used to uniquely identify real-world objects. primary natural surrogate foreign

Natural

A(n)_____ is a generic entity type that is related to one or more entity subtypes. inheritance subtype discriminator entity supertype specialization hierarchy

entity supertype

The default comparison condition for the subtype discriminator attribute is the _____ comparison. equality greater than less than nonequality

equality

Overlapping subtypes are subtypes that contain _____ subsets of the supertype entity set. null exclusive nonunique solitary

nonunique

A _____ is a primary key created by a database designer to simplify the identification of entity instances. compound key composite key natural key surrogate key

surrogate key

The "_____" characteristic of a primary key states that the primary key must uniquely identify each entity instance, must be able to guarantee unique values, and must not contain nulls. security-complaint unique values preferably single-attribute nonintelligent

unique values

At the implementation level, the supertype and its subtype(s) depicted in a specialization hierarchy maintain a(n) _____ relationship. M:N 1:M self-referencing 1:1

1:1

An entity cluster is formed by combining multiple interrelated entities into _____. multiple abstract entity objects multiple entity objects a single abstract entity object a single entity object

A single abstract entity object

A partial completeness constraint is represented by _____. a dotted line a single horizontal line under a circle two dashed lines a double horizontal line over a circle

A single horizontal line under a circle

In the context of total completeness, in a(n) _____, every supertype occurrence is a member of only one subtype. overlapping constraint disjoint constraint foreign key constraint nonunique constraint

Disjoint constraint

A total completeness constraint is represented by a _____. smaller circle inside a bigger circle double horizontal line under a circle single horizontal line above a circle rhombus inside a circle

Double horizontal line under a circle

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

False

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

False

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

False

_____ is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity subtypes. Total completeness Specialization Generalization Normalization

Generalization

The property of _____ enables an entity subtype to inherit the attributes and relationships of the supertype. specialization hierarchy inheritance entity supertype subtype discriminator

Inheritance

Composite primary keys are particularly useful as identifiers of composite entities, where each primary key combination is allowed only once in the _____ relationship. 1:M 1:1 M:N 0:1

M:N

If one exists, a data modeler uses a _____ as the primary key of the entity being modeled. foreign key surrogate key natural identifier combination key

Natural identifier

The "_____" characteristic of a primary key states that the primary key should not have embedded semantic meaning. nonintelligent security-compliant preferably single-attribute unique values

Nonintelligent

Within a specialization hierarchy, every subtype can have _____ supertype(s) to which it is directly related. only one many one or many zero

Only one

In the context of total completeness, in a(n) _____, every supertype occurrence is a member of at least one subtype. unique constraint overlapping constraint foreign key constraint disjoint constraint

Overlapping constraint

The most important characteristic of an entity is its _____ key, used to uniquely identify each entity instance. natural foreign primary surrogate

Primary

According to the "preferably single-attribute" characteristic of a primary key, the primary key: should have the minimum number of attributes possible. must be able to guarantee unique attribute values. should have embedded semantic meaning associated with each attribute. must be composed of attributes that are free from security risks or violations.

Should have the minimum number of attributes possible.

The _____ depicts the arrangement of higher-level entity supertypes (parent entities) and lower-level entity subtypes (child entities). entity supertype specialization hierarchy inheritance subtype discriminator

Specialization hierarchy

A(n) _____ is the attribute in the supertype entity that determines to which entity subtype each supertype occurrence is related. entity supertype inheritance discriminator subtype discriminator specialization hierarchy

Subtype discriminator

Which of the following is a specialization hierarchy disjoint constraint scenario in case of partial completeness? Each supertype occurrence is a member of at least one subtype. Each supertype occurrence is a member of only one subtype. Subtype discriminator can be null. Subtype discriminator cannot be null.

Subtype discriminator can be null.

Which of the following is a specialization hierarchy overlapping constraint scenario in case of partial completeness? Subtype sets are unique. Supertype has optional subtypes. Subtype discriminators cannot be null. Subtype does not have a supertype.

Supertype has optional subtypes.

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. False True

True

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

True

An entity supertype can have disjoint or overlapping entity subtypes. True False

True

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

True

Entity supertypes and subtypes are organized in a specialization hierarchy. True False

True

Implementing overlapping subtypes requires the use of one discriminator attribute for each subtype. True False

True

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

True

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

True

The completeness constraint can be partial or total. False True

True

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

True

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

True

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

Unique

The purpose of an entity _____ is to simplify an entity-relationship diagram (ERD) and thus enhance its readability. constraint interface cluster discriminator

cluster

The extended entity relationship model (EERM) is sometimes referred to as the _____. enclosed entity relationship model extended entity relationship diagram entity clustering relationship model enhanced entity relationship model

enhanced entity relationship model

A specialization hierarchy can have _____ level(s) of supertype/subtype relationships. one or many many zero only one

many

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

primary

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 violation. nonintelligent preferably single-attribute security-compliant unique values

security-compliant