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Exam 5: Advanced Data Modeling

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Question 31

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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

E) A) and B)
F) B) and C)

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Question 32

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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

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Question 33

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

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

Entity supertypes and subtypes are organized in a specialization hierarchy.

A(n) _____ is a generic entity type that is related to one or more entity subtypes.

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.

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.

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

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

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

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

An entity cluster is considered "virtual" or "_____" in the sense that it is not actually an entity in the final ERD.

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

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

Explain the "no change over time" characteristic of a primary key.

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.

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.

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

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