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ISE 224 > Chapter 5 > Flashcards

Chapter 5 Flashcards

1
Q

A data model is a plan for a database design.

A

True

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2
Q

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

A

True

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3
Q

An entity is something that users want to track.

A

True

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4
Q

Entities of a given type are grouped into entity classes.

A

True

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5
Q

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

A

True

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6
Q

An entity instance is the occurrence of a particular entity.

A

True

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7
Q

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.

A

True

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8
Q

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

A

True

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9
Q

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

A

False

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10
Q

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

A

True

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11
Q

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

A

False

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12
Q

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

A

False

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13
Q

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

A

False

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14
Q

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

A

False

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15
Q

Entities can be associated with one another in relationships.

A

True

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16
Q

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

A

True

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17
Q

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

A

False

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18
Q

Relationships of degree two are referred to as binary relationships.

A

True

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19
Q

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

A

True

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20
Q

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

A

False

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21
Q

A single relationship class involves only one entity class.

A

False

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22
Q

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

A

False

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23
Q

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

A

False

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24
Q

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

A

True

25
Q

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

A

True

26
Q

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

A

False

27
Q

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

A

True

28
Q

Relationships are classified by their cardinality.

A

True

29
Q

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

A

False

30
Q

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

A

True

31
Q

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

A

False

32
Q

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.

A

True

33
Q

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

A

True

34
Q

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

A

True

35
Q

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

A

False

36
Q

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

A

True

37
Q

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

A

True

38
Q

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

A

True

39
Q

ID-dependent entities are associated by a nonidentifying relationship.

A

False

40
Q

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.

A

True

41
Q

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

A

True

42
Q

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

A

True

43
Q

Subtype entities contain only attributes unique to the subtypes.

A

True

44
Q

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

A

True

45
Q

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

A

False

46
Q

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

A

True

47
Q

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

A

True

48
Q

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

A

False

49
Q

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

A

True

50
Q

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

A

False

51
Q

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

A

False

52
Q

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

A

False

53
Q

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

A

True

54
Q

Subtypes can be exclusive or inclusive.

A

True

55
Q

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

A

True

56
Q

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

A

False

57
Q

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

A

True

58
Q

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

A

False

ISE 224 (8 decks)

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