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Exam 5: Advanced Data Modeling

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Question 41

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What do specialization hierarchies do?

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Entity supertypes and subtypes are organ...

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Question 42

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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.

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Question 43

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

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.

An entity supertype can have disjoint or overlapping entity subtypes.

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

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.

A subtype contains attributes that are common to all of its supertypes.

In the context of total completeness,in a(n) ,every supertype occurrence is a member of at least one subtype.

Overlapping subtypes are subtypes that contain subsets of the supertype entity set.

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.

is a generic entity type that is related to one or more entity subtypes.

Differentiate between specialization and generalization.

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

The function of the primary key is to describe an entity.

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.

A primary key's main function is to uniquely identify a(n) within a table.

Describe an entity cluster.

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