Deck 5: Data Modeling With the Entity-Relationship Model

Question 1

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

Answer 1

True

Question 2

A data model is a plan for a database design.

Answer 2

True

Question 3

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

Answer 3

True

Question 4

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

Question 5

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

Question 6

An entity is something that users want to track.

Question 7

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

Question 8

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.

Question 9

Entities of a given type are grouped into entity classes.

Question 10

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

Question 11

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

Question 12

Entities can be associated with one another in relationships.

Question 13

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

Question 14

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

Question 15

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

Question 16

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

Question 17

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

Question 18

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

Question 19

An entity instance is an occurrence of a particular entity.

Question 20

Relationships of degree two are referred to as binary relationships.

Question 21

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

Question 22

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

Question 23

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

Question 24

A single relationship class involves only one entity class.

Question 25

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

Question 26

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.

Question 27

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.

Question 28

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

Question 29

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

Question 30

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

Question 31

ID-dependent entities are associated by a nonidentifying relationship.

Question 32

Relationships are classified by their cardinality.

Question 33

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

Question 34

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

Question 35

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

Question 36

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

Question 37

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

Question 38

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

Question 39

The notation 1:N shows a relationship's maximum cardinalities.

Question 40

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

Question 41

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

Question 42

Subtype entities contain,apart from the identifier,only attributes that do not appear in the supertype.

Question 43

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

Question 44

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

Question 45

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

Question 46

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

Question 47

Which of the following is not a key element of an E-R model?

A)Relationships
B)Entities
C)Objects
D)Attributes

Question 48

Which of the following is not a good reason for designing a data model?

A)It's easier to change things in the data model than it is in the actual DBMS.
B)The data model provides a simplified view of the database that can be shown to people who don't need to see all the details.
C)Creating a data model will help you understand the application area better.
D)The data model can be discarded after the database is operational.

Question 49

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

Question 50

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

Question 51

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

Question 52

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

Question 53

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

Question 54

Entities containing multivalued attributes are often represented using subtypes.

Question 55

Subtypes can be exclusive or inclusive.

Question 56

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

Question 57

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

Question 58

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

Question 59

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

Question 60

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

Question 61

Attributes may be ________.

A)complete
B)optional
C)multivalued
D)required

Question 62

You are given an E-R diagram with two entities,ORDER and CUSTOMER,as shown above,and are asked to draw the relationship between them.If a given customer can place many orders and a given order can be placed by one or more customers,which of the following should be indicated in the relationship symbol between the two entities?

A)N:M
B)1:1
C)1:N
D)N:1

Question 63

For a relationship to be considered a binary relationship it must satisfy which of the following conditions?

A)It must involve exactly two entity classes.
B)It must have a maximum cardinality of 1:1.
C)It must have a maximum cardinality of 1:N.
D)Both A and B are correct

Question 64

An entity whose identifier includes the identifier of another entity is a(n)________.

A)strong entity
B)weak entity
C)optional entity
D)required entity

Question 65

You are given an E-R diagram with two entities,ORDER and CUSTOMER,as shown above.What does the symbol next to the CUSTOMER entity indicate?

A)A maximum cardinality of "zero"
B)A maximum cardinality of "one"
C)A minimum cardinality of "optional"
D)A minimum cardinality of "required"

Question 66

You are given an E-R diagram with two entities,ORDER and CUSTOMER,as shown above,and are asked to draw the relationship between them.If a given customer can place only one order and a given order can be placed by at most one customer,which of the following should be indicated in the relationship symbol between the two entities?

A)N:M
B)1:1
C)1:N
D)N:1

Question 67

You are given an E-R diagram with two entities,ORDER and CUSTOMER,as shown above.What does the symbol next to the ORDER entity indicate?

A)A maximum cardinality of "zero"
B)A maximum cardinality of "one"
C)A minimum cardinality of "optional"
D)A minimum cardinality of "required"

Question 68

An occurrence of a particular entity is called an ________.

A)entity class
B)entity relationship
C)entity instance
D)entity attribute

Question 69

An identifier may be ________.

A)composite
B)optional
C)a relationship
D)minimal

Question 70

An entity whose existence depends on the presence of another entity but whose identifier does not include the identifier of the other entity is a(n)________.

A)strong entity
B)weak entity
C)ID-dependent entity
D)subtype entity

Question 71

Minimum cardinality refers to ________.

A)the most instances of one entity class that can be involved in a relationship with one instance of another entity class
B)the minimum number of entity classes involved in a relationship
C)whether or not an instance of one entity class is required to be related to an instance of another entity class
D)whether or not an entity is a weak entity

Question 72

A hash mark across the relationship line near an entity indicates ________.

A)a maximum cardinality of "zero"
B)a maximum cardinality of "one"
C)a minimum cardinality of "optional"
D)a minimum cardinality of "required"

Question 73

Entities of a given type are grouped into an ________.

A)entity class
B)entity relationship
C)entity instance
D)entity attribute

Question 74

A composite attribute is an attribute that ________.

A)is multivalued
B)describes a characteristic of the relationship
C)consists of a group of attributes
D)is calculated at run-time

Question 75

A circle across the relationship line near an entity indicates ________.

A)a maximum cardinality of "zero"
B)a maximum cardinality of "one"
C)a minimum cardinality of "optional"
D)a minimum cardinality of "required"

Question 76

You are given an E-R diagram with two entities,ORDER and CUSTOMER,as shown above,and are asked to draw the relationship between them.If a given customer can place many orders and a given order can be placed by at most one customer,which of the following should be indicated in the relationship symbol between the two entities?

A)N:M
B)1:1
C)1:N
D)N:1

Question 77

Which of the following is not a common variant of the E-R model?

A)IE Crow's Foot
B)IDEF1X
C)UML
D)Object-oriented

Question 78

Maximum cardinality refers to ________.

A)the most instances of one entity class that can be involved in a relationship instance with another entity class
B)the minimum number of entity classes involved in a relationship
C)whether or not an instance of one entity class is required to be related to an instance of another entity class
D)whether or not an entity is a weak entity

Question 79

In a minimum cardinality,minimums are generally stated as ________.

A)0 or 1
B)1 or N
C)M or N
D)one or many

Question 80

The characteristics of a thing are described by its ________.

A)identifiers
B)entities
C)objects
D)attributes