Deck 8: Data Modeling Advanced Concepts

Question 1

An entity supertype can have disjoint or overlapping entity subtypes.

Answer 1

True

Question 2

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

Answer 2

True

Question 3

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

Answer 3

False

Question 4

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

Question 5

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

Question 6

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

Question 7

Some designs use redundant relationships as a way to simplify the design.

Question 8

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

Question 9

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

Question 10

The entity supertype contains the common characteristics and the entity subtypes contain the unique characteristics of each entity subtype.

Question 11

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

Question 12

In specialization hierarchies with multiple levels of supertype/subtypes, a lower-level supertype inherits all of the attributes and relationships from all of its upper-level subtypes.

Question 13

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

Question 14

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 15

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

Question 16

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

Question 17

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

Question 18

Generalization is based on grouping unique characteristics and relationships of the subtypes.

Question 19

Entity supertypes and subtypes are organized in a specialization hierarchy.

Question 20

The completeness constraint can be partial or total.

Question 21

Non-overlapping subtypes are subtypes that contain a(n) ____ subset of the supertype entity set.

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

Question 22

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 23

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 24

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 25

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

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

Question 26

Partial completeness is symbolized by ____.

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

Question 27

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 28

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

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

Question 29

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

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

Question 30

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 31

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

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

Question 32

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 33

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 34

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

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

Question 35

The primary key's main function is to uniquely identify a(n) ____ within a table.

A) attribute
B) entity instance or row
C) entity subtype
D) natural identifier

Question 36

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 37

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 38

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

A) not equality
B) less than
C) greater than
D) equality

Question 39

____ is a generic entity type that is related to one or more entity subtypes.

A) A subtype discriminator
B) Inheritance
C) A specialization hierarchy
D) An entity supertype

Question 40

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 41

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

Question 42

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

Question 43

Surrogate primary keys are especially helpful when there is no ____ key.

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

Question 44

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

Question 45

The preferred placement for a foreign key when working with a 1:1 relationship is to ____.

A) use the same primary key for both entities
B) create a bridge entity
C) place a foreign key in one of the entities
D) place a foreign key in both entities

Question 46

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

Question 47

The "____" characteristic of a primary key states the following: The PK must uniquely identify each entity instance. A primary key must be able to guarantee unique values. It cannot contain nulls.

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

Question 48

The "____" characteristic of a primary key states the following: The PK should not have embedded semantic meaning. An attribute with embedded semantic meaning is probably better used as a descriptive characteristic of the entity rather than as an identifier.

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

Question 49

The "____" characteristic of a primary key states the following: The selected primary key must not be composed of any attribute(s) that might be considered a security risk or violation. For example, using a Social Security number as a PK in an EMPLOYEE table is not a good idea.

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

Question 50

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

A) Foreign
B) Composite
C) Natural
D) Surrogate

Question 51

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

Question 52

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

Question 53

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

Question 54

A ____ 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.

A) surrogate primary keys
B) time-variant data
C) design trap
D) fan trap

Question 55

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

Question 56

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

Question 57

Disjoint subtypes are also known as ____________________ subtypes.

Question 58

When selecting a foreign key placement for a 1:1 relationship, place the PK of the entity on the mandatory side in the entity on the optional side as a FK, and make the FK mandatory when ____.

A) one side is mandatory and the other side is optional
B) one side participates in another relationship
C) both sides are optional
D) both sides are mandatory

Question 59

____ relationships occur when there are multiple relationship paths between related entities.

A) Redundant
B) Duplicated
C) Time-variant
D) Supertype

Question 60

____ data refer to data whose values change over time and for which you must keep a history of the data changes.

A) Time-sensitive
B) Time-variant
C) Historical
D) Change-based

Question 61

The most common design trap is known as a(n) ____________________.

Question 62

In what two cases are composite primary keys particularly useful?

Question 63

Describe specialization and generalization.

Question 64

If you use a surrogate key, you must ensure that the candidate key of the entity in question performs properly through the use of the "____________________" and "not null" constraints.

Question 65

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

Question 66

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

Question 67

What is an entity cluster?

Question 68

What do specialization hierarchies do?

Question 69

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

Question 70

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