Cierto o falso de Capitulo 4

Question 1

E-R models are expressed using a single standardized set of universally accepted symbols.

Accepted Answer

false

Answer

true

Question 2

An entity is something in the users’ work environment that the users want to track.

Accepted Answer

true

Question 3

Entities of a given type are grouped into entity classes.

Accepted Answer

true

Question 4

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

Accepted Answer

true

Question 5

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.

Accepted Answer

true

Question 6

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

Accepted Answer

false

Answer

true

Question 7

In E-R modeling, an attribute may be either composite or multi-valued, but it cannot be both.

Accepted Answer

false

Answer

true

Question 8

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

Accepted Answer

false

Answer

true

Question 9

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

Accepted Answer

false

Answer

true

Question 10

An identifier may be either unique or nonunique.

Accepted Answer

true

Question 11

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

Accepted Answer

true

Question 12

Relationships do not have attributes.

Accepted Answer

false

Answer

true

Question 13

A single relationship class involves only one entity class.

Accepted Answer

false

Answer

true

Question 14

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

Accepted Answer

false

Answer

true

Question 15

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

Accepted Answer

false

Answer

true

Question 16

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

Accepted Answer

true

Question 17

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

Accepted Answer

false

Answer

true

Question 18

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.

Accepted Answer

true

Question 19

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

Accepted Answer

true

Question 20

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

Accepted Answer

true

Question 21

Multi-valued attributes are represented in E-R diagrams by creating a new weak entity to represent the multi-valued attribute and creating a 1:N relationship.

Accepted Answer

true

Question 22

Subtype entities are used to produce a closer-fitting model when an entity has sets of optional attributes.

Accepted Answer

true

Question 23

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

Accepted Answer

true

Question 24

Inheritance in a generalization hierarchy means that the supertype entity inherits all the attributes of the subtype entity.

Accepted Answer

false

Answer

true

Question 25

It is not important to document business rules during data modeling since they will be enforced by the application programs.

Accepted Answer

false

Answer

true

Question 26

UML is intended for modeling and designing object-oriented programs and applications.

Accepted Answer

true

Question 27

For database design, UML-style E-R diagrams must be treated very differently from traditional E-R diagrams because of their object-oriented background.

Accepted Answer

true

Question 28

Maximum cardinalities are represented in UML-style E-R diagrams with the same notation (1:1, 1:N, N:M) as in traditional E-R diagrams.

Accepted Answer

false

Answer

true

Question 29

In UML-style E-R diagrams, a weak entity is shown by placing a filled-in diamond on the parent of the weak entity.

Accepted Answer

true

Question 30

One weakness of UML-style E-R diagrams is that there is no means of distinguishing between a weak entity that is ID-dependent and a weak entity that is not ID-dependent.

Accepted Answer

false

Answer

true

Question 31

UML-style E-R diagrams allow for the existence of class attributes, which are attributes that pertain to the collection of all entities within that class not to the individual entity instances

Accepted Answer

true

Question 32

UML-style E-R diagrams allow for three different levels of visibility of attributes.

Accepted Answer

true

Question 33

UML-style E-R diagrams introduce object-oriented notation that is of limited practical value in traditional, relational database design.

Accepted Answer

true

Question 34

The goal of data models is to strive to produce the most accurate model of the real world as possible.

Accepted Answer

false

Answer

true

Nächster

Cierto o falso de Capitulo 4

Beschreibung

Zusammenfassung der Ressource

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