Chapter 5

Question 1

A data model is a plan for a database design.

Answer 1

True

Question 2

The method of constructing data models used in the text is the extended entity-relationship (E-R) model.

Answer 2

True

Question 3

An entity is something that users want to track.

Answer 3

True

Question 4

Entities of a given type are grouped into entity classes.

Answer 4

True

Question 5

An entity class is described by the structure of the entities in that class.

Answer 5

True

Question 6

An entity instance is the occurrence of a particular entity.

Answer 6

True

Question 7

An entity instance of an entity class is the representation of a particular entity and is described by the values of the attributes of the entity.

Answer 7

True

Question 8

An identifier of an entity instance is one or more attributes that name or identify entity instances.

Answer 8

True

Question 9

A compound identifier is an identifier consisting of two or more attributes.

Answer 9

False

Question 10

In E-R modeling, an attribute describes the characteristics of an entity.

Answer 10

True

Question 11

In E-R modeling, entities within an entity class may have different attributes.

Answer 11

False

Question 12

An identifier of an entity instance must consist of one and only one attribute.

Answer 12

False

Question 13

A composite identifier is defined as a composite attribute that is an identifier.

Answer 13

False

Question 14

An identifier serves the same role for a table that a key does for an entity.

Answer 14

False

Question 15

Entities can be associated with one another in relationships.

Answer 15

True

Question 16

The degree of a relationship is the number of entity classes in the relationship.

Answer 16

True

Question 17

A binary relationship is a relationship between two or more entities.

Answer 17

False

Question 18

Relationships of degree two are referred to as binary relationships.

Answer 18

True

Question 19

E-R modeling recognizes both relationship classes and relationship instances.

Answer 19

True

Question 20

In today’s E-R models, attributes of relationships are still used.

Answer 20

False

Question 21

A single relationship class involves only one entity class.

Answer 21

False

Question 22

A binary relationship is a relationship based on numerical entity instance identifiers.

Answer 22

False

Question 23

The degree of a relationship is expressed as the relationship’s maximum cardinality.

Answer 23

False

Question 24

When transforming a data model into a relational design, relationships of all degrees are treated as combinations of binary relationships.

Answer 24

True

Question 25

The principal difference between an entity and a table is that you can express a relationship between entities without using foreign keys.

Answer 25

True

Question 26

When designing a database, first identify the entities, then determine the attributes, and finally create the relationships.

Answer 26

False

Question 27

The notation 1:N shows the relationship's maximum cardinality.

Answer 27

True

Question 28

Relationships are classified by their cardinality.

Answer 28

True

Question 29

A relationship's maximum cardinality indicates the maximum number of entities that can participate in the relationship.

Answer 29

False

Question 30

In an E-R model, the three types of maximum cardinality are 1:1, 1:N and N:M.

Answer 30

True

Question 31

In a 1:N relationship, the term parent refers to the N side of the relationship.

Answer 31

False

Question 32

In a 1:N relationship, the parent entity is on the one side of the relationship, and the child entity is on the many side of the relationship.

Answer 32

True

Question 33

A relationship's minimum cardinality indicates the number of entity instances that must participate in the relationship.

Answer 33

True

Question 34

A relationship's minimum cardinality indicates whether or not an entity must participate in the relationship.

Answer 34

True

Question 35

In an E-R model, the three types of minimum cardinality are mandatory, optional and indeterminate.

Answer 35

False

Question 36

An entity that represents something that can exist on its own is called a strong entity.

Answer 36

True

Question 37

E-R models use an identifying relationship to connect entities that are ID-dependent.

Answer 37

True

Question 38

An ID-dependent entity is an entity whose identifier includes the identifier of another entity.

Answer 38

True

Question 39

ID-dependent entities are associated by a nonidentifying relationship.

Answer 39

False

Question 40

A weak entity is an entity that cannot exist in the database without (and is logically dependent upon) another type of entity also existing in the database.

Answer 40

True

Question 41

) ID-dependent entities are a common type of weak entity.

Answer 41

True

Question 42

All weak entities must have a minimum cardinality of 1 on the entity on which it depends.

Answer 42

True

Question 43

Subtype entities contain only attributes unique to the subtypes.

Answer 43

True

Question 44

An attribute that determines which subtype is appropriate is called a discriminator.

Answer 44

True

Question 45

An exclusive subtype pattern has one supertype entity that relates to one or more subtype entities.

Answer 45

False

Question 46

Entities with an IS-A relationship should have the same identifier.

Answer 46

True

Question 47

One example of a database design using an ID-dependent relationship is the association pattern.

Answer 47

True

Question 48

One example of a database design using a strong relationship is the multivalued attribute pattern.

Answer 48

False

Question 49

One example of a database design using an ID-dependent relationship is the archetype/instance pattern.

Answer 49

True

Question 50

Data modelers agree that weak, non-ID-dependent entities exist and are important.

Answer 50

False

Question 51

Entities containing optional sets of attributes are often represented using subtypes.

Answer 51

False

Question 52

The supremetype entity contains the attributes that are common to all subtypes.

Answer 52

False

Question 53

An attribute that determines which subtype is appropriate is called a discriminator.

Answer 53

True

Question 54

Subtypes can be exclusive or inclusive.

Answer 54

True

Question 55

Relationships between supertypes and subtypes are called IS-A relationships.

Answer 55

True

Question 56

Relationships among instances of a single entity class are called redundant relationships.

Answer 56

False

Question 57

There are three types of recursive relationships: 1:1, 1:N and N:M.

Answer 57

True

Question 58

Recursive relationships only exist for one-to-one relationships.

Answer 58

False