DBMS Chapter 8 Flashcards

1
Q

Enhanced-ER (EER) Model Concepts

A

Includes all concepts of ERD
plus sub/superclasses, specialization/generalization,
attribute inheritance, categories

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2
Q

subclass

A
An entity that inherits all attributes of the entity as a member of the superclass 
It also inherits all relationships
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3
Q

Superclass

A

entity type that may have additional subgroupings

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4
Q

Specialization

A

Is the process of defining a set of subclasses of a superclass

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5
Q

Generalization

A
generilizing common features in several classes
EX: vehicle is a superclass to car and truck
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6
Q

3 Constraints on Specialization and Generalization

A

predicate-defined (or condition-defined) subclasses
attribute defined-specialization
user-defined specialization

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7
Q

Disjointness Constraint:

A

This means that an entity can be a member of at most one of the subclasses of the specialization. If not disjointed they overlap; signified with a d or an o

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8
Q

Completeness Constraint

A
Total specifies that every entity in the superclass must be a member of some subclass in the specialization/ generalization.
 signified with double line ==
Partial allows an entity not to belong to any of the subclasses 
signified with single line ---
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9
Q

what is the requirement. to determine if entities are condition-defined subclasses?

A

If we can determine exactly those entities that will become members of each subclass by a condition

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10
Q

what is the requirement. to determine if entities are attribute-defined subclasses?

A

If all subclasses in a specialization have membership condition on same attribute of the superclass

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11
Q

what is the requirement. to determine if entities are user-defined subclasses?

A

If no condition determines membership

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12
Q

Hierarchy specialization

A

Hierarchy has a constraint that every subclass has only one superclass. Creates tree structure

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13
Q

Lattice Specialization

A

a subclass can be subclass of more than one superclass (called multiple inheritance). Creates a diamond structure

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14
Q

Union Type use:

A
to model a single superclass/subclass relationship with more than one superclass : denoted with horseshoe and U
Example: owner of a car(person, bank, company)
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