Question 1

An entity supertype can have disjoint or overlapping entity subtypes.

Accepted Answer

An entity supertype can have both disjoint and overlapping entity subtypes. Disjoint subtypes have unique sets of attributes, and each entity can belong to only one subtype. Overlapping subtypes share some common attributes, and each entity can belong to multiple subtypes.

Question 2

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

Accepted Answer

Specialization involves identifying more specific entity subtypes from a higher-level entity supertype. This is a top-down process as it involves starting from a general category and then identifying more specific subcategories within it.

Question 3

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

Accepted Answer

Overlapping subtypes are subtypes where an entity instance of the supertype can belong to more than one subtype, not exclusively to a unique subset.

Question 4

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

Accepted Answer

Entity subtypes inherit the relationships in which the supertype entity participates.

Question 5

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

Accepted Answer

The answer of The property of subtype discriminator enables an...

Question 6

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

Accepted Answer

The answer of To model time-variant data, you must create...

Question 7

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

Accepted Answer

Redundant relationships can help eliminate the need for extra tables or columns by duplicating information in multiple places, making the design more streamlined and easier to work with.

Question 8

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

Accepted Answer

The answer of Implementing non-overlapping subtypes requires the use of...

Question 9

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

Accepted Answer

This ensures that each entity instance can be uniquely identified, regardless of its subtype.

Question 10

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

Accepted Answer

This statement accurately describes the concept of supertypes and subtypes in entity-relationship modeling.

Question 11

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

Accepted Answer

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

Question 12

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.

Accepted Answer

The answer of In specialization hierarchies with multiple levels of...

Question 13

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

Accepted Answer

The "is-a" relationship describes how a subclass is a specific type of its superclass. This is the primary relationship depicted in a specialization hierarchy.

Question 14

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.

Accepted Answer

A design trap occurs when a relationship is improperly or incompletely identified, leading to inconsistent representation in the real world.

Question 15

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

Accepted Answer

Disjoint subtypes are subtypes where each entity instance of the supertype can belong to only one subtype, meaning their subsets do not overlap.

Question 16

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

Accepted Answer

The answer of At the implementation level, the supertype and...

Question 17

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

Accepted Answer

Entity clusters are used to group entities and relationships in the ERD, and they are treated as a single entity type.

Question 18

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

Accepted Answer

The answer of Generalization is based on grouping unique characteristics...

Question 19

Entity supertypes and subtypes are organized in a specialization hierarchy.

Accepted Answer

Entity supertypes and subtypes are indeed organized in a specialization hierarchy where the supertype represents a higher-level abstraction and the subtype represents a more specific variation of the supertype.

Question 20

The completeness constraint can be partial or total.

Accepted Answer

The completeness constraint can be partially satisfied if there are missing or unknown values, or it can be totally satisfied if every attribute has a value for every tuple in the relation.

Quiz 8: Data Modeling Advanced Concepts