Deck 5: Advanced Data Modeling

Question 1

Disjoint subtypes are subtypes that contain nonunique subsets of the supertype entity set.

Answer 1

False

Question 2

One important inheritance characteristic is that all entity subtypes inherit their primary key attribute from their supertype.

Answer 2

True

Question 3

The property of a subtype discriminator enables an entity supertype to inherit the attributes and relationships of the subtype.

Answer 3

False

Question 4

In specialization hierarchies with multiple levels of supertype and subtypes, a lower-level subtype can inherit only a few of the attributes and relationships from its upper-level supertypes.

Question 5

Implementing overlapping subtypes requires the use of one discriminator attribute for each subtype.

Question 6

Entity subtypes do not inherit the relationships in which the supertype entity participates.

Question 7

An entity supertype can have disjoint or overlapping entity subtypes.

Question 8

The relationships depicted within the specialization hierarchy are sometimes described in terms of "is-a" relationships.

Question 9

At the implementation level, the supertype and its subtype(s) depicted in the specialization hierarchy maintain a 1:1 relationship.

Question 10

A subtype contains attributes that are common to all of its supertypes.

Question 11

The function of the primary key is to describe an entity.

Question 12

A design trap occurs when a relationship is improperly or incompletely identified and is therefore represented in a way that is not consistent with the real world.

Question 13

Entity supertypes and subtypes are organized in a specialization hierarchy.

Question 14

Overlapping subtypes are subtypes that contain a unique subset of the supertype entity set.

Question 15

The entity supertype contains common characteristics, and the entity subtypes each contain their own unique characteristics.

Question 16

Within a specialization hierarchy, a supertype can exist only within the context of a subtype.

Question 17

Specialization is the top-down process of identifying lower-level, more specific entity subtypes from a higher-level entity supertype.

Question 18

To model time-variant data, one must create a new entity in an M:N relationship with the original entity.

Question 19

The completeness constraint can be partial or total.

Question 20

An entity cluster is a "virtual" entity type used to represent multiple entities and relationships in the ERD.

Question 21

Which of the following is a specialization hierarchy disjoint constraint scenario in case of partial completeness?

A) Subtype discriminator can be null.
B) Subtype discriminator cannot be null.
C) Each supertype occurrence is a member of only one subtype.
D) Each supertype occurrence is a member of at least one subtype.

Question 22

One important inheritance characteristic is that all entity subtypes inherit their _____ key attribute from their supertype.

A) primary
B) natural
C) foreign
D) surrogate

Question 23

In the context of total completeness, in a(n) _____, every supertype occurrence is a member of at least one subtype.

A) unique constraint
B) disjoint constraint
C) overlapping constraint
D) foreign key constraint

Question 24

Within a specialization hierarchy, every subtype can have _____ supertype(s) to which it is directly related.

A) zero
B) only one
C) one or many
D) many

Question 25

A specialization hierarchy can have _____ level(s) of supertype/subtype relationships.

A) zero
B) only one
C) one or many
D) many

Question 26

Nonoverlapping subtypes are subtypes that contain a(n) _____ subset of the supertype entity set.

A) entity
B) subtypes
C) unique
D) nonunique

Question 27

At the implementation level, the supertype and its subtype(s) depicted in a specialization hierarchy maintain a(n) _____ relationship.

A) self-referencing
B) 1:1
C) 1:M
D) M:N

Question 28

Overlapping subtypes are subtypes that contain _____ subsets of the supertype entity set.

A) null
B) exclusive
C) solitary
D) nonunique

Question 29

A(n) _____ is the attribute in the supertype entity that determines to which entity subtype each supertype occurrence is related.

A) subtype discriminator
B) inheritance discriminator
C) specialization hierarchy
D) entity supertype

Question 30

The default comparison condition for the subtype discriminator attribute is the _____ comparison.

A) nonequality
B) less than
C) greater than
D) equality

Question 31

A partial completeness constraint is represented by _____.

A) a dotted line
B) two dashed lines
C) a single horizontal line under a circle
D) a double horizontal line over a circle

Question 32

The purpose of an entity_____ is to simplify an entity-relationship diagram (ERD) and thus enhance its readability.

A) constraint
B) cluster
C) interface 
D) discriminator 

Question 33

A(n)_____ is a generic entity type that is related to one or more entity subtypes.

A) subtype discriminator
B) inheritance
C) specialization hierarchy
D) entity supertype

Question 34

In the context of total completeness, in a(n) _____, every supertype occurrence is a member of only one subtype.

A) foreign key constraint
B) nonunique constraint
C) overlapping constraint
D) disjoint constraint

Question 35

The property of _____ enables an entity subtype to inherit the attributes and relationships of the supertype.

A) subtype discriminator
B) inheritance
C) specialization hierarchy
D) entity supertype

Question 36

The extended entity relationship model (EERM) is sometimes referred to as the _____.

A) enclosed entity relationship model
B) enhanced entity relationship model
C) entity clustering relationship model
D) extended entity relationship diagram

Question 37

Which of the following is a specialization hierarchy overlapping constraint scenario in case of partial completeness?

A) Subtype sets are unique.
B) Supertype has optional subtypes.
C) Subtype discriminators cannot be null.
D) Subtype does not have a supertype.

Question 38

The _____ depicts the arrangement of higher-level entity supertypes (parent entities) and lower-level entity subtypes (child entities).

A) subtype discriminator
B) inheritance
C) specialization hierarchy
D) entity supertype

Question 39

A total completeness constraint is represented by a _____.

A) smaller circle inside a bigger circle
B) rhombus inside a circle
C) double horizontal line under a circle
D) single horizontal line above a circle

Question 40

_____ is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity subtypes.

A) Specialization
B) Generalization
C) Normalization
D) Total completeness

Question 41

_____ completeness means that not every supertype occurrence is a member of a subtype.

Question 42

An entity cluster is formed by combining multiple interrelated entities into _____.

A) a single abstract entity object
B) multiple abstract entity objects
C) a single entity object
D) multiple entity objects

Question 43

The _____ is the result of adding more semantic constructs to the original entity relationship (ER) model.

Question 44

The "_____" characteristic of a primary key states that the selected primary key must not be composed of any attribute(s) that might be considered a violation.

A) unique values
B) nonintelligent
C) preferably single-attribute
D) security-compliant

Question 45

A _____ key is a real-world, generally accepted identifier used to uniquely identify real-world objects.

A) primary
B) natural
C) foreign
D) surrogate

Question 46

Specialization is based on grouping _____ characteristics and relationships of the subtypes.

Question 47

Unique values can be better managed when they are _____, because the database can use internal routines to implement a counter-style attribute that automatically increments values with the addition of each new row.

Question 48

An entity cluster is considered "virtual" or "_____" in the sense that it is not actually an entity in the final ERD.

Question 49

The "_____" characteristic of a primary key states that the primary key should not have embedded semantic meaning.

A) unique values
B) nonintelligent
C) preferably single-attribute
D) security-compliant

Question 50

The "_____" characteristic of a primary key states that the primary key must uniquely identify each entity instance, must be able to guarantee unique values, and must not contain nulls.

A) unique values
B) nonintelligent
C) preferably single-attribute
D) security-complaint

Question 51

If one exists, a data modeler uses a _____ as the primary key of the entity being modeled.

A) foreign key
B) combination key
C) surrogate key
D) natural identifier

Question 52

Usually, a data modeler uses a natural identifier as the _____ of the entity being modeled, assuming that the entity has a natural identifier.

Question 53

A _____ is a primary key created by a database designer to simplify the identification of entity instances.

A) composite key
B) compound key
C) natural key
D) surrogate key

Question 54

The _____ specifies whether each entity supertype occurrence must also be a member of at least one subtype.

Question 55

According to the "preferably single-attribute" characteristic of a primary key, the primary key:

A) must be able to guarantee unique attribute values.
B) should have the minimum number of attributes possible.
C) should have embedded semantic meaning associated with each attribute.
D) must be composed of attributes that are free from security risks or violations.

Question 56

Subtypes that contain nonunique subsets of the supertype entity set are known as _____ subtypes.

Question 57

The most important characteristic of an entity is its _____ key, used to uniquely identify each entity instance.

A) primary
B) natural
C) foreign
D) surrogate

Question 58

_____ completeness means that every supertype occurrence must be a member of at least one subtype.

Question 59

Composite primary keys are particularly useful as identifiers of composite entities, where each primary key combination is allowed only once in the _____ relationship.

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

Question 60

Disjoint subtypes are also known as _____ subtypes.

Question 61

Explain the two criteria that help a designer in determining when to use subtypes and supertypes.

Question 62

A(n) _____ occurs when you have one entity in two 1:M relationships to other entities, thus producing an association among the other entities that is not expressed in the model.

Question 63

A weak entity in a strong identifying relationship with a parent entity is normally used to represent a(n) _____ that is represented in the data model as two separate entities.

Question 64

From a data modeling point of view, _____ data refer to data whose values change over time and for which one must keep a history of the data changes.

Question 65

Composite primary keys are particularly useful as identifiers of composite entities, where each primary key combination is allowed _____ in the M:N relationship.

Question 66

A(n) _____ occurs when a relationship is improperly or incompletely identified and is therefore represented in a way that is not consistent with the real world.

Question 67

In which two cases are composite primary keys particularly useful?

Question 68

While using a surrogate key, one must ensure that the candidate key of the entity in question performs properly through the use of the "_____" and "not null" constraints.

Question 69

_____ keys work with primary keys to properly implement relationships in the relational model.

Question 70

Composite keys are useful as identifiers of weak entities, where the weak entity has a strong _____ relationship with the parent entity.

Question 71

Differentiate between specialization and generalization.

Question 72

The main concern with redundant relationships is that they remain _____ across the model.

Question 73

One practical advantage of a(n) _____ key is that because it has no intrinsic meaning, values for it can be generated by the DBMS to ensure that unique values are always provided.

Question 74

Explain the "no change over time" characteristic of a primary key.

Question 75

What do specialization hierarchies do?