CHAPTER 5: ADVANCED DATA MODELING
1. The entity supertype contains common characteristics, and the entity subtypes each contain their own unique
characteristics.
a. True
b. False
2. Entity supertypes and subtypes are organized in a specialization hierarchy.
a. True
b. False
3. The relationships depicted within the specialization hierarchy are sometimes described in terms of “is-a”
relationships.
a. True
b. False
4. Within a specialization hierarchy, a supertype can exist only within the context of a subtype.
a. True
b. False
5. One important inheritance characteristic is that all entity subtypes inherit their primary key attribute from their
supertype.
a. True
b. False
6. A subtype contains attributes that are common to all of its supertypes.
a. True
b. False
7. At the implementation level, the supertype and its subtype(s) depicted in the specialization hierarchy maintain
a 1:1 relationship.
a. True
b. False
8. Entity subtypes do not inherit the relationships in which the supertype entity participates.
a. True
b. False
Chapter 5: Advanced Data Modeling
9. 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.
a. True
b. False
10. The property of a subtype discriminator enables an entity supertype to inherit the attributes and relationships of
the subtype.
a. True
b. False
11. An entity supertype can have disjoint or overlapping entity subtypes.
a. True
b. False
12. Disjoint subtypes are subtypes that contain nonunique subsets of the supertype entity set.
a. True
b. False
13. Overlapping subtypes are subtypes that contain a unique subset of the supertype entity set.
a. True
b. False
14. Implementing overlapping subtypes requires the use of one discriminator attribute for each subtype.
a. True
b. False
15. Implementing nonoverlapping subtypes requires the use of one discriminator attribute for each subtype.
a. True
b. False
16. The completeness constraint can be partial or total.
a. True
b. False
Chapter 5: Advanced Data Modeling
17. Specialization is the top-down process of identifying lower-level, more specific entity subtypes from a higher-
level entity supertype.
a. True
b. False
18. Generalization is based on grouping unique characteristics and relationships of the subtypes.
a. True
b. False
19. An entity cluster is a “virtual” entity type used to represent multiple entities and relationships in the ERD.
a. True
b. False
20. The function of the primary key is to describe an entity.
a. True
b. False
21. To model time-variant data, one must create a new entity in an M:N relationship with the original entity.
a. True
b. False
22. 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.
a. True
b. False
23. Some designs use redundant relationships as a way to simplify the design.
a. True
b. False
24. 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
Chapter 5: Advanced Data Modeling
25. 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
26. 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
27. 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
28. A specialization hierarchy can have level(s) of supertype/subtype relationships.
a. zero b. only one
c. one or many d. many
29. 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
30. One important inheritance characteristic is that all entity subtypes inherit their key attribute from their
supertype.
a. primary b. natural
c. foreign d. surrogate
31. 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
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
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33. The default comparison condition for the subtype discriminator attribute is the comparison.
a. nonequality b. less than
c. greater than d. equality
34. 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.
35. 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.
36. Nonoverlapping subtypes are subtypes that contain a(n) subset of the supertype entity set.
a. entity b. subtypes
c. unique d. nonunique
37. Overlapping subtypes are subtypes that contain subsets of the supertype entity set.
a. null b. exclusive
c. solitary d. nonunique
38. A total completeness constraint is represented by .
a. a smaller circle inside a bigger circle
b. a rhombus inside a circle
c. a double horizontal line under a circle
d. a single horizontal line above a circle
39. 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
Chapter 5: Advanced Data Modeling
40. 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
41. 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
42. 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
43. The purpose of a(n) is to simplify an entity-relationship diagram (ERD) and thus enhance its readability.
a. entity constraint
b. entity cluster
c. entity interface
d. entity discriminator
44. 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
45. 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
Chapter 5: Advanced Data Modeling
46. A key is a real-world, generally accepted identifier used to uniquely identify real-world objects.
a. primary b. natural
c. foreign d. surrogate
47. 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
48. 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
49. A 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 key or identifier
50. 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
51. 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
52. 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
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53. 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.
54. 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
55. Surrogate primary keys are especially helpful when there is no key.
a. primary b. natural
c. foreign d. composite
56. keys work with primary keys to properly implement relationships in the relational model.
a. Foreign b. Composite
c. Natural d. Surrogate
57. 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 the foreign key in one of the entities
d. place the surrogate key in both entities
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
Chapter 5: Advanced Data Modeling
59. data refer to data whose values change over time and for which one must keep a history of the data
changes.
a. Time-sensitive b. Time-variant
c. Historical d. Change-based
60. 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.
a. surrogate primary key b. time-variant data
c. design trap d. fan trap
61. relationships occur when there are multiple relationship paths between related entities.
a. Redundant b. Duplicated
c. Time-variant d. Supertype
62. The is the result of adding more semantic constructs to the original entity relationship (ER) model.
63. Disjoint subtypes are also known as subtypes.
64. Subtypes that contain nonunique subsets of the supertype entity set are known as subtypes.
65. The specifies whether each entity supertype occurrence must also be a member of at least one subtype.
66. completeness means that not every supertype occurrence is a member of a subtype.
67. completeness means that every supertype occurrence must be a member of at least one subtype.
68. Specialization is based on grouping characteristics and relationships of the subtypes.
Chapter 5: Advanced Data Modeling
69. An entity cluster is considered “virtual” or “ ” in the sense that it is not actually an entity in the final
ERD.
70. Usually, a data modeler uses a natural identifier as the of the entity being modeled, assuming that the
entity has a natural identifier.
71. 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.
72. Composite primary keys are particularly useful as identifiers of composite entities, where each primary key
combination is allowed in the M:N relationship.
73. 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.
74. Composite keys are useful as identifiers of weak entities, where the weak entity has a strong relationship
with the parent entity.
75. 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.
76. 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.
77. 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.
78. 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.
79. The main concern with redundant relationships is that they remain across the model.
Chapter 5: Advanced Data Modeling
80. What do specialization hierarchies do?
81. Differentiate between specialization and generalization.
82. Explain the two criteria that help a designer in determining when to use subtypes and supertypes.
83. Describe an entity cluster.
84. Explain the “no change over time” characteristic of a primary key.
85. In which two cases are composite primary keys particularly useful?