Database Systems Design Implementation And Management 11th Edition by Carlos Coronel – Test Bank

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CHAPTER 5:  ADVANCED DATA MODELING

 

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

 

ANSWER:  True

 

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

 

ANSWER:  True

 

  1. The relationships depicted within the specialization hierarchy are sometimes described in terms of “is­a”

relationships.

  1. True
  2. False

 

ANSWER:  True

 

  1. Within a specialization hierarchy, a supertype can exist only within the context of a subtype.
    1. True
    2. False

 

ANSWER:  False

 

  1. One important inheritance characteristic is that all entity subtypes inherit their primary key attribute from their
    1. True
    2. False

 

ANSWER:  True

 

  1. A subtype contains attributes that are common to all of its supertypes.
    1. True
    2. False

 

ANSWER:  False

 

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

 

ANSWER:  True

 

  1. Entity subtypes do not inherit the relationships in which the supertype entity participates.
    1. True
    2. False

 

ANSWER:  False

  1. 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.
    1. True
    2. False

 

ANSWER:  False

 

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

 

ANSWER:  False

 

  1. An entity supertype can have disjoint or overlapping entity subtypes.
    1. True
    2. False

 

ANSWER:  True

 

  1. Disjoint subtypes are subtypes that contain nonunique subsets of the supertype entity set.
    1. True
    2. False

 

ANSWER:  False

 

  1. Overlapping subtypes are subtypes that contain a unique subset of the supertype entity set.
    1. True
    2. False

 

ANSWER:  False

 

  1. Implementing overlapping subtypes requires the use of one discriminator attribute for each subtype.
    1. True
    2. False

 

ANSWER:  True

 

  1. Implementing nonoverlapping subtypes requires the use of one discriminator attribute for each subtype.
    1. True
    2. False

 

ANSWER:  False

 

  1. The completeness constraint can be partial or total.
    1. True
    2. False

 

ANSWER:  True

 

 

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

 

ANSWER:  True

 

  1. Generalization is based on grouping unique characteristics and relationships of the subtypes.
    1. True
    2. False

 

ANSWER:  False

 

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

 

ANSWER:  True

 

  1. The function of the primary key is to describe an entity.
    1. True
    2. False

 

ANSWER:  False

 

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

 

ANSWER:  False

 

  1. 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.
    1. True
    2. False

 

ANSWER:  True

 

  1. Some designs use redundant relationships as a way to simplify the design.
    1. True
    2. False

 

ANSWER:  True

 

  1. The extended entity relationship model (EERM) is sometimes referred to as the .
    1. enclosed entity relationship model enhanced entity relationship model
    2. entity clustering relationship model d. extended entity relationship diagram

 

ANSWER:  b

 

 

  1.          is a generic entity type that is related to one or more entity subtypes.
    1. A subtype discriminator Inheritance
    2. A specialization hierarchy d. An entity supertype

 

ANSWER:  d

 

  1. The depicts the arrangement of higher-level entity supertypes (parent entities) and lower-level entity subtypes (child entities).
    1. subtype discriminator inheritance
    2. specialization hierarchy d. entity supertype

 

ANSWER:  c

 

  1. Within a specialization hierarchy, every subtype can have supertype(s) to which it is directly related.
    1. zero only one
    2. one or many d. many

 

ANSWER:  b

 

  1. A specialization hierarchy can have level(s) of supertype/subtype relationships.
    1. zero only one
    2. one or many d. many

 

ANSWER:  d

 

  1. The property of enables an entity subtype to inherit the attributes and relationships of the supertype.
    1. subtype discriminator inheritance
    2. specialization hierarchy d. entity supertype

 

ANSWER:  b

 

  1. One important inheritance characteristic is that all entity subtypes inherit their key attribute from their
    1. primary natural
    2. foreign d. surrogate

 

ANSWER:  a

 

  1. At the implementation level, the supertype and its subtype(s) depicted in a specialization hierarchy maintain a(n)
    1. self-referencing 1:1
    2. 1:M d. M:N

 

ANSWER:  b

 

  1. A(n) is the attribute in the supertype entity that determines to which entity subtype each supertype occurrence is related.
    1. subtype discriminator inheritance discriminator
    2. specialization hierarchy d. entity supertype

 

ANSWER:  a

  1. The default comparison condition for the subtype discriminator attribute is the
    1. nonequality less than
    2. greater than d. equality

 

ANSWER:  d

 

  1. Which of the following is a specialization hierarchy disjoint constraint scenario in case of partial completeness?
    1. Subtype discriminator can be null.
    2. Subtype discriminator cannot be null.
    3. Each supertype occurrence is a member of only one subtype.
    4. Each supertype occurrence is a member of at least one subtype.

 

ANSWER:  a

 

  1. Which of the following is a specialization hierarchy overlapping constraint scenario in case of partial completeness?
    1. Subtype sets are unique.
    2. Supertype has optional subtypes.
    3. Subtype discriminators cannot be null.
    4. Subtype does not have a supertype.

 

ANSWER:  b

 

  1. Nonoverlapping subtypes are subtypes that contain a(n) subset of the supertype entity set.
    1. entity subtypes
    2. unique d. nonunique

 

ANSWER:  c

 

  1. Overlapping subtypes are subtypes that contain subsets of the supertype entity set.
    1. null exclusive
    2. solitary d. nonunique

 

ANSWER:  d

 

  1. A total completeness constraint is represented by .
    1. a smaller circle inside a bigger circle
    2. a rhombus inside a circle
    3. a double horizontal line under a circle
    4. a single horizontal line above a circle

 

ANSWER:  c

 

  1. A partial completeness constraint is represented by .
    1. a dotted line two dashed lines
    2. a single horizontal line under a circle d. a double horizontal line over a circle

 

ANSWER:  c

  1. In the context of total completeness, in a(n) , every supertype occurrence is a member of only one subtype.
    1. foreign key constraint
    2. nonunique constraint
    3. overlapping constraint
    4. disjoint constraint

 

ANSWER:  d

 

  1. In the context of total completeness, in a(n) , every supertype occurrence is a member of at least one
    1. unique constraint
    2. disjoint constraint
    3. overlapping constraint
    4. foreign key constraint

 

ANSWER:  c

 

  1.          is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity
    1. Specialization Generalization
    2. Normalization d. Total completeness

 

ANSWER:  b

 

  1. The purpose of a(n) is to simplify an entity-relationship diagram (ERD) and thus enhance its readability.
    1. entity constraint
    2. entity cluster
    3. entity interface
    4. entity discriminator

 

ANSWER:  b

 

  1. An entity cluster is formed by combining multiple interrelated entities into .
    1. a single abstract entity object multiple abstract entity objects
    2. a single entity object d. multiple entity objects

 

ANSWER:  a

 

  1. The most important characteristic of an entity is its key, used to uniquely identify each entity instance.
    1. primary natural
    2. foreign d. surrogate

 

ANSWER:  a

 

 

  1. A key is a real-world, generally accepted identifier used to uniquely identify real-world objects.
    1. primary natural
    2. foreign d. surrogate

 

ANSWER:  b

 

  1. If one exists, a data modeler uses a as the primary key of the entity being modeled.
    1. foreign key combination key
    2. surrogate key d. natural identifier

 

ANSWER:  d

 

  1. A is a primary key created by a database designer to simplify the identification of entity instances.
    1. composite key
    2. compound key
    3. natural key
    4. surrogate key

 

ANSWER:  d

 

  1. A primary key’s main function is to uniquely identify a(n) within a table.
    1. attribute entity instance or row
    2. entity subtype d. natural key or identifier

 

ANSWER:  b

 

  1. Composite primary keys are particularly useful as identifiers of composite entities, where each primary key combination is allowed only once in the
  2. 0:1 b. 1:1
  3. 1:M d. M:N

 

ANSWER:  d

 

  1. 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.
    1. unique values nonintelligent
    2. preferably single-attribute d. security-complaint

 

ANSWER:  a

 

  1. 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.

  1. unique values nonintelligent
  2. preferably single-attribute d. security-compliant

 

ANSWER:  d

 

 

  1. According to the “preferably single­attribute” characteristic of a primary key, the primary key:
    1. must be able to guarantee unique attribute values.
    2. should have the minimum number of attributes possible.
    3. should have embedded semantic meaning associated with each attribute.
    4. must be composed of attributes that are free from security risks or violations.

 

ANSWER:  b

 

  1. The “ ” characteristic of a primary key states that the primary key should not have embedded semantic meaning.
    1. unique values nonintelligent
    2. preferably single-attribute d. security-compliant

 

ANSWER:  b

 

  1. Surrogate primary keys are especially helpful when there is no
    1. primary natural
    2. foreign d. composite

 

ANSWER:  b

 

  1.          keys work with primary keys to properly implement relationships in the relational model.
    1. Foreign Composite
    2. Natural d. Surrogate

 

ANSWER:  a

 

  1. The preferred placement for a foreign key when working with a 1:1 relationship is to .
    1. use the same primary key for both entities
    2. create a bridge entity
    3. place the foreign key in one of the entities
    4. place the surrogate key in both entities

 

ANSWER:  c

 

  1. 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 .
    1. one side is mandatory and the other side is optional
    2. one side participates in another relationship
    3. both sides are optional
    4. both sides are mandatory

 

ANSWER:  a

 

 

  1.          data refer to data whose values change over time and for which one must keep a history of the data
    1. Time-sensitive Time-variant
    2. Historical d. Change-based

 

ANSWER:  b

 

  1. A occurs when there is 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.
    1. surrogate primary key time-variant data
    2. design trap d. fan trap

 

ANSWER:  d

 

  1.          relationships occur when there are multiple relationship paths between related entities.
    1. Redundant Duplicated
    2. Time-variant d. Supertype

 

ANSWER:  a

 

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

ANSWER:   extended entity relationship model (EERM)

EERM (extended entity relationship model)

extended entity relationship model

EERM

 

  1. Disjoint subtypes are also known as

ANSWER:  non-overlapping

nonoverlapping

 

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

ANSWER:  overlapping

 

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

ANSWER:  completeness constraint

 

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

ANSWER:  Partial

 

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

ANSWER:  Total

 

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

ANSWER:  unique

 

 

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

ANSWER:  abstract

 

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

ANSWER:  primary key

 

  1. 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.

ANSWER:  numeric

 

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

ANSWER:  only once

once

 

  1. 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.

ANSWER:  real-world object

 

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

ANSWER:  identifying

 

  1. 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.

ANSWER:  surrogate

 

  1. 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.

ANSWER:  unique index

 

  1. 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.

ANSWER:  time-variant

 

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

ANSWER:  design trap

 

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

ANSWER:  consistent

 

 

  1. What do specialization hierarchies do?

ANSWER:  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.

 

  1. Differentiate between specialization and generalization.

ANSWER:  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 the unique characteristics and relationships of the subtypes. On the other hand, 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 the common characteristics and relationships of the subtypes.

 

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

ANSWER:  Two criteria help a designer determine when to use subtypes and supertypes:

 

  1. There must be different, identifiable kinds or types of an entity in the user’s environment.

 

  1. The different kinds or types of instances should each have one or more attributes that are unique to that kind or type of instance.

 

  1. Describe an entity cluster.

ANSWER:  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.

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

ANSWER:  If an attribute has semantic meaning, it might be subject to updates, which is why names do not make good primary keys. 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 one is basically changing the identity of an entity. In short, the PK should be permanent and unchangeable.

  1. In which two cases are composite primary keys particularly useful?

ANSWER:  Composite primary keys are particularly useful in two cases:

 

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

 

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

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