Database Principles Fundamentals of Design, Implementation and Management, International Edition 9th Edition by Carlos Corone - Test Bank

Database Principles Fundamentals of Design, Implementation and Management, International Edition 9th Edition by Carlos Corone – Test Bank

 

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Sample Questions Are Posted Below

 

Chapter 5: Advanced Data Modeling

 

TRUE/FALSE

 

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

 

ANS:  T                    PTS:   1

 

2. Entity supertypes and subtypes are organized in a specialization hierarchy.

 

ANS:  T                    PTS:   1

 

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

 

ANS:  T                    PTS:   1

 

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

 

ANS:  F                    PTS:   1

 

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

 

ANS:  T                    PTS:   1

 

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

 

ANS:  T                    PTS:   1

 

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

 

ANS:  F                    PTS:   1

 

8. 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.

 

ANS:  F                    PTS:   1

 

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

 

ANS:  F                    PTS:   1

 

10. An entity supertype can have disjoint or overlapping entity subtypes.

 

ANS:  T                    PTS:   1

 

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

 

ANS:  F                    PTS:   1

 

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

 

ANS:  F                    PTS:   1

 

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

 

ANS:  F                    PTS:   1

 

14. The completeness constraint can be partial or total.

 

ANS:  T                    PTS:   1

 

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

 

ANS:  T                    PTS:   1

 

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

 

ANS:  F                    PTS:   1

 

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

 

ANS:  T                    PTS:   1

 

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

 

ANS:  F                    PTS:   1

 

19. 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.

 

ANS:  T                    PTS:   1

 

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

 

ANS:  T                    PTS:   1

 

MULTIPLE CHOICE

 

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

a.	entity relationship model	c.	entity clustering relationship model
b.	enhanced entity relationship model	d.	extended entity relationship diagram

 

 

ANS:  B                    PTS:   1

 

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

a.	A subtype discriminator	c.	A specialization hierarchy
b.	Inheritance	d.	An entity supertype

 

 

ANS:  D                    PTS:   1

 

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

a.	subtype discriminator	c.	specialization hierarchy
b.	inheritance	d.	entity supertype

 

 

ANS:  C                    PTS:   1

 

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

a.	subtype discriminator	c.	specialization hierarchy
b.	inheritance	d.	entity supertype

 

 

ANS:  C                    PTS:   1

 

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

a.	zero	c.	one or many
b.	only one	d.	many

 

 

ANS:  B                    PTS:   1

 

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

a.	zero	c.	one or many
b.	only one	d.	many

 

 

ANS:  D                    PTS:   1

 

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

a.	subtype discriminator	c.	specialization hierarchy
b.	inheritance	d.	entity supertype

 

 

ANS:  B                    PTS:   1

 

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

a.	primary	c.	foreign
b.	natural	d.	surrogate

 

 

ANS:  A                    PTS:   1

 

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

a.	self-referencing	c.	1:M
b.	1:1	d.	M:N

 

 

ANS:  B                    PTS:   1

 

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

a.	subtype discriminator	c.	specialization hierarchy
b.	inheritance discriminator	d.	entity supertype

 

 

ANS:  A                    PTS:   1

 

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

a.	not equality	c.	greater than
b.	less than	d.	equality

 

 

ANS:  D                    PTS:   1

 

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

a.	entity	c.	unique
b.	subtypes	d.	nonunique

 

 

ANS:  C                    PTS:   1

 

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

a.	entity	c.	unique
b.	subtypes	d.	nonunique

 

 

ANS:  D                    PTS:   1

 

14. Partial completeness is symbolized by ____.

a.	a dotted line	c.	a circle over a single line
b.	two dashed lines	d.	a circle over a double line

 

 

ANS:  C                    PTS:   1

 

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

a.	Specialization	c.	Partial completeness
b.	Generalization	d.	Total completeness

 

 

ANS:  B                    PTS:   1

 

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

a.	a single abstract entity object	c.	a single entity object
b.	multiple abstract entity object	d.	multiple entity objects

 

 

ANS:  A                    PTS:   1

 

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

a.	primary	c.	foreign
b.	natural	d.	surrogate

 

 

ANS:  A                    PTS:   1

 

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

a.	primary	c.	foreign
b.	natural	d.	surrogate

 

 

ANS:  B                    PTS:   1

 

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

a.	foreign key	c.	surrogate key
b.	combination key	d.	natural identifier

 

 

ANS:  D                    PTS:   1

 

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

a.	attribute	c.	entity subtype
b.	entity instance or row	d.	natural identifier

 

 

ANS:  B                    PTS:   1

 

21. 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	c.	preferably single-attribute
b.	nonintelligent	d.	security complaint

 

 

ANS:  A                    PTS:   1

 

22. 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	c.	preferably single-attribute
b.	nonintelligent	d.	security compliant

 

 

ANS:  D                    PTS:   1

 

23. 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	c.	preferably single-attribute
b.	nonintelligent	d.	security compliant

 

 

ANS:  B                    PTS:   1

 

24. 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	c.	1:M
b.	1:1	d.	M:N

 

 

ANS:  D                    PTS:   1

 

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

a.	primary	c.	foreign
b.	natural	d.	composite

 

 

ANS:  B                    PTS:   1

 

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

a.	Foreign	c.	Natural
b.	Composite	d.	Surrogate

 

 

ANS:  A                    PTS:   1

 

27. 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

 

 

ANS:  C                    PTS:   1

 

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

a.	Time-sensitive	c.	Historical
b.	Time-variant	d.	Change-based

 

 

ANS:  B                    PTS:   1

 

29. 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	c.	design trap
b.	time-variant data	d.	fan trap

 

 

ANS:  D                    PTS:   1

 

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

a.	Redundant	c.	Time-variant
b.	Duplicated	d.	Supertype

 

 

ANS:  A                    PTS:   1

 

COMPLETION

 

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

 

ANS:

extended entity relationship model (EERM)

extended entity relationship model

EERM

 

PTS:   1

 

2. Disjoint subtypes are also known as ____________________ subtypes.

 

ANS:

non-overlapping

nonoverlapping

 

PTS:   1

 

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

 

ANS:  overlapping subtypes

 

PTS:   1

 

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

 

ANS:  completeness

 

PTS:   1

 

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

 

ANS:  Partial

 

PTS:   1

 

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

 

ANS:  Total

 

PTS:   1

 

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

 

ANS:  unique

 

PTS:   1

 

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

 

ANS:  abstract

 

PTS:   1

 

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

 

ANS:  primary key

 

PTS:   1

 

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

 

ANS:

only once

once

 

PTS:   1

 

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

 

ANS:  identifying

 

PTS:   1

 

12. 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.

 

ANS:  unique index

 

PTS:   1

 

13. 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.

 

ANS:  time-variant data

 

PTS:   1

 

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

 

ANS:  fan trap

 

PTS:   1

 

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

 

ANS:  consistent

 

PTS:   1

 

ESSAY

 

1. What do specialization hierarchies do?

 

ANS:

Entity supertypes and subtypes are organized in a specialization hierarchy, which depicts the arrangement of higher-level entity supertypes (parent entities) and lower-level entity subtypes (child entities).

Specialization hierarchies enable the data model to capture additional semantic content (meaning) into the ERD.

A specialization hierarchy provides the means to:

Support attribute inheritance.

Define a special supertype attribute known as the subtype discriminator.

Define disjoint/overlapping constraints and complete/partial constraints.

 

PTS:   1                    TOP:   Critical Thinking

 

2. Describe specialization and generalization.

 

ANS:

Specialization is the top-down process of identifying lower-level, more specific entity subtypes from a higher-level entity supertype. Specialization is based on grouping unique characteristics and relationships of the subtypes. In the aviation example, you used specialization to identify multiple entity subtypes from the original employee supertype.

Generalization is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity subtypes. Generalization is based on grouping common characteristics and relationships of the subtypes. For example, you might identify multiple types of musical instruments: piano, violin, and guitar. Using the generalization approach, you could identify a “string instrument” entity supertype to hold the common characteristics of the multiple subtypes.

 

PTS:   1                    TOP:   Critical Thinking

 

3. What is an entity cluster?

 

ANS:

An entity cluster is a “virtual” entity type used to represent multiple entities and relationships in the ERD. An entity cluster is formed by combining multiple interrelated entities into a single abstract entity object. An entity cluster is considered “virtual” or “abstract” in the sense that it is not actually an entity in the final ERD. Instead, it is a temporary entity used to represent multiple entities and relationships, with the purpose of simplifying the ERD and thus enhancing its readability.

 

PTS:   1                    TOP:   Critical Thinking

 

4. Explain the “no change over time” characteristic of a good primary key.

 

ANS:

If an attribute has semantic meaning, it might be subject to updates. This is why names do not make good primary keys. If you have Vickie Smith as the primary key, what happens when she gets married? If a primary key is subject to change, the foreign key values must be updated, thus adding to the database work load. Furthermore, changing a primary key value means that you are basically changing the identity of an entity. In short, the PK should be permanent and unchangeable.

 

PTS:   1                    TOP:   Critical Thinking

 

5. In what two cases are composite primary keys particularly useful?

 

ANS:

As identifiers of composite entities, where each primary key combination is allowed only once in the M:N relationship.

As identifiers of weak entities, where the weak entity has a strong identifying relationship with the parent entity.

 

PTS:   1                    TOP:   Critical Thinking