Enhanced Entity Relationship Schema Flashcards

1
Q

IS A

A

Type of relationship (employee is a user)

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2
Q

Inheritance

A

One entity is derived from another (subclass).
Shown via C connection.

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3
Q

Specialisation (top-down)

A

Attributes/relationships only apply to certain but not all members of entity type

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4
Q

Generalisation

A

Main idea is to suppress differences between entity types
Common features

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5
Q

Attribute-defined subclass

A

Can define what will be inherited.
Outside of connection line.

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6
Q

Predicate-defined subclass

A

The rule that defines it / attribute extended
If subclass is professional, then Job Type (the attribute-defined subclass) = “Professional”

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7
Q

Disjoint Constraints

A

A subclass of a specialisation is disjoint ; comparing the connected subclasses

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8
Q

Disjoint

A

Either one or the other (d)

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9
Q

Overlapping

A

Could be more than one (o)

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10
Q

Double line

A

Must be classified (has to either be salaried or hourly-paid)

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11
Q

Single line

A

Does not need to be an employee or a professional

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