Chapter 05: Advanced Data Modeling
True / False
1. The entity supertype contains common characteristics, and the entity subtypes each contain their own unique
characteristics.
a. True
b. Fals
e
ANSWER: True
DIFFICULTY: Difficulty: Easy
REFERENCES: 5-1a Entity Supertypes and Subtypes
LEARNING OBJ
ECTIVES:
05.01 -
Describe the main extended entity relationship (EER) model constructs and
how they are represented in ERDs and EERDs
2. Entity supertypes and subtypes are organized in a specialization hierarchy.
a. True
b. Fals
e
ANSWER: True
DIFFICULTY: Difficulty: Easy
REFERENCES: 5-1b Specialization Hierarchy
LEARNING OBJ
ECTIVES:
05.01 -
Describe the main extended entity relationship (EER) model constructs and
how they are represented in ERDs and EERDs
3. The relationships depicted within the specialization hierarchy are sometimes described in terms of “is-a” relationships.
a. True
b. Fals
e
ANSWER: True
DIFFICULTY: Difficulty: Moderate
REFERENCES: 5-1b Specialization Hierarchy
LEARNING OBJ
ECTIVES:
05.01 -
Describe the main extended entity relationship (EER) model constructs and
how they are represented in ERDs and EERDs
4. Within a specialization hierarchy, a supertype can exist only within the context of a subtype.
a. True
b. Fals
e
ANSWER: False
DIFFICULTY: Difficulty: Easy
REFERENCES: 5-1b Specialization Hierarchy
LEARNING OBJ
ECTIVES:
05.01 -
Describe the main extended entity relationship (EER) model constructs and
how they are represented in ERDs and EERDs
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____ 1. Entity supertypes and subtypes are organized in a specialization hierarchy.
____2.The relationships depicted within the specialization hierarchy are sometimes described in terms of is-a relationships.
____3.Within an specialization
hierarchy, a supertype can exist only within the context of a subtype.
____4.The entity supertype contains the common characteristics and the entity subtypes contain the unique characteristics of each entity subtype.
____5.The property of subtype discriminator enables an entity supertype to inherit the attributes and relationships of the subtype.
____6.One important inheritance characteristic is that all entity subtypes inherit their primary key attribute from their supertype.
____7.At the implementation level, the supertype and its subtype(s) depicted in the specialization hierarchy maintain a 1:1 relationship.
____8.Entity subtypes do not inherit the relationships in which the
supertype entity participates.
____9.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 subtype.
____10.An entity supertype can have disjoint or overlapping entity subtypes.
____11.Overlapping
subtypes are subtypes that contain a unique subset of the supertype entity set.
____12.Disjoint subtypes are subtypes that contain nonunique subsets of the supertype entity set.
____13.Implementing non-overlapping subtypes requires the use of one discriminator attribute for each subtype.
____14.The completeness
constraint can be partial or total.
____15.Specialization is the top-down process of identifying lower-level, more specific entity subtypes from a higher-level entity supertype.
____16.Generalization is based on grouping unique characteristics and relationships of the subtypes.
____17.An entity cluster is a "virtual"
entity type used to represent multiple entities and relationships in the ERD.
____18.To model time-variant data, you must create a new entity in a M:N relationship with the original entity.
____19.A design trap occurs when a relationship is improperly or incompletely identified and, therefore, is represented in a way that is not consistent with the real world.
____20.Some designs use redundant relationships as a way to simplify the design.
Do subtypes inherit relationships?
What important inheritance characteristic that all entity subtypes inherit from their supertype?
Term The property of _____ enables an entity subtype to inherit the attributes and relationships of the supertype. | Definition inheritance |
Term | Definition primary |
Term One important inheritance characteristic is that all entity subtypes inherit their primary key attribute from their supertype. | Definition True |