Deck 5: Advanced Data Modeling

Question 1

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

Answer 1

False

Question 2

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

Answer 2

False

Question 3

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

Answer 3

True

Question 4

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

Question 5

Entity supertypes and subtypes are organized in a specialization hierarchy.

Question 6

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

Question 7

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

Question 8

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

Question 9

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

Question 10

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

Question 11

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

Question 12

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

Question 13

An entity supertype can have disjoint or overlapping entity subtypes.

Question 14

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

Question 15

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 16

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

Question 17

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 18

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

Question 19

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

Question 20

The completeness constraint can be partial or total.

Question 21

____ 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 22

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 23

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 24

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

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

Question 25

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

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

Question 26

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 27

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 28

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 29

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 30

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

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

Question 31

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 32

____ 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 33

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 34

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

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

Question 35

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

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

Question 36

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 37

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

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

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

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 40

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 41

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 42

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

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

Question 43

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 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 44

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

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

Question 45

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

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

Question 46

The "____" characteristic of a primary key states that:
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 47

____ 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 48

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

Question 49

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

Question 50

The "____" characteristic of a primary key states that:
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 51

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

Question 52

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

Question 53

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

Question 54

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

Question 55

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

Question 56

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 57

Disjoint subtypes are also known as ____________________ subtypes.

Question 58

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

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

Question 61

Describe specialization and generalization.

Question 62

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

Question 63

What is an entity cluster?

Question 64

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

Question 65

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

Question 66

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

Question 67

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

Question 68

In what two cases are composite primary keys particularly useful?

Question 69

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

Question 70

What do specialization hierarchies do?