Deck 5: Data Modeling With the Entity-Relationship Model

Question 1

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

Answer 1

True

Question 2

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

Answer 2

False

Question 3

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

Answer 3

False

Question 4

Entities can be associated with one another in relationships.

Question 5

An entity instance is the occurrence of a particular entity.

Question 6

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

Question 7

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

Question 8

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

Question 9

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

Question 10

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

Question 11

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

Question 12

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

Question 13

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

Question 14

Entities of a given type are grouped into entity classes.

Question 15

A data model is a plan for a database design.

Question 16

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 17

An entity is something that users want to track.

Question 18

Relationships of degree two are referred to as binary relationships.

Question 19

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

Question 20

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

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 parent entity is on the one side of the relationship,and the child entity is on the many side of the relationship.

Question 23

ID-dependent entities are associated by a nonidentifying relationship.

Question 24

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 25

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

Question 26

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

Question 27

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

Question 28

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

Question 29

Relationships are classified by their cardinality.

Question 30

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

Question 31

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

Question 32

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

Question 33

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

Question 34

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

Question 35

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

Question 36

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

Question 37

A single relationship class involves only one entity class.

Question 38

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

Question 39

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

Question 40

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

Question 41

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

Question 42

Entities of a given type are grouped into an ________.

A)entity class
B)entity relationship
C)entity instance
D)entity attribute
E)None of the above.

Question 43

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

Question 44

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

Question 45

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

Question 46

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

Question 47

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

Question 48

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

Question 49

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

Question 50

Subtypes can be exclusive or inclusive.

Question 51

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

Question 52

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

Question 53

Subtype entities contain only attributes unique to the subtypes.

Question 54

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

Question 55

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

Question 56

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

Question 57

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

Question 58

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

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

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 a strong relationship is the multivalued attribute pattern.

Question 61

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)0:1
B)1:1
C)1:N
D)N:1
E)N:M

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 at most one customer,which of the following should be indicated in the relationship symbol between the two entities?

A)0:1
B)1:1
C)1:N
D)N:1
E)N:M

Question 63

Which of the following is considered to be a weak entity?

A)ID-dependent entity
B)subtype entity
C)association entity
D)B and C
E)A,B,and C

Question 64

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
E)is an identifier

Question 65

An identifier may be ________.

A)composite
B)a single attribute
C)a relationship
D)A and B
E)A,B,and C

Question 66

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
E)None of the above.

Question 67

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

A)0
B)1
C)N
D)A or B
E)A,B,or C

Question 68

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

A)strong entity
B)weak entity
C)ID-dependent entity
D)A and C
E)B and C

Question 69

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"
E)None of the above.

Question 70

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)0:1
B)1:1
C)1:N
D)N:1
E)N:M

Question 71

The occurrence of a particular entity is called an ________.

A)entity class
B)entity relationship
C)entity instance
D)entity attribute
E)None of the above.

Question 72

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
E)None of the above.

Question 73

Attributes may be ________.

A)composite
B)element
C)multivalued
D)A and C
E)B and C

Question 74

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"
E)None of the above.

Question 75

The characteristics of a thing are described by its ________.

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

Question 76

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)A and B
E)A and C

Question 77

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"
E)None of the above.

Question 78

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)A and C
E)B and C

Question 79

Common variants of the E-R model include:

A)IE Crow's Foot
B)IDEF1X
C)UML
D)A and B
E)A,B,and C

Question 80

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"
E)None of the above.