jarrar: subtype relations and constraints

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Subtype Relations and Constraints

Knowledge Engineering (SCOM7348)

© Mustafa JarrarLecture Notes, Knowledge Engineering (SCOM7348)

University of Birzeit1st Semester, 2011

Dr. Mustafa JarrarUniversity of Birzeitmjarrar@birzeit.edu

www.jarrar.info

(Chapter 6)

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Conceptual Schema Design Steps

1. From examples to elementary facts

2. Draw fact types and apply population check

3. Combine entity types

4. Add uniqueness constraints

5. Add mandatory constraints

6. Add subtype relations and other constraints

7. Final checks, & schema engineering issues

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Outline

• Quick Math background

• Value Constraints

• Set Constrains

o Subset

o Equality

o Exclusion

• Subtype relations

• Frequency constraints

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Mathematical Background

Hypothetical Euler diagrams for set comparisons.

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Venn diagrams for three set-forming operations.

Mathematical Background

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Mathematical Background

Venn diagrams for (a) A is a proper subset of B and (b) four sets.

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Outline

• Quick Math background

• Value Constraints

• Set Constrains

o Subset

o Equality

o Exclusion

• Subtype relations

• Frequency constraints

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Value Constraint

Called Value Constraint

A set of values, from which the value of the MedalKind is limited to

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Value Constraint

The value of sex should be one of {‘M’, ‘F’}

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Value Constraint

Value constraints may list the possible values of a value type.

Who can give more examples?

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Outline

• Quick Math background

• Value Constraints

• Set Constrains

o Subset

o Equality

o Exclusion

• Subtype relations

• Frequency constraints

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Role subset/equality constraint

Subset constraint:Every Member booked an Hour should play sport.

Equality constraint:Every Member ‘has’ ReactionTime should ‘has’ HeartRate, and every Member ‘has’ HeartRate should ‘has’ ReactionTime.

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Role subset constraint

Notice that this subset constraint is implied, and should be removed.

That is, there is no need to say that every A playing r2 must also play r1 (subset), because the mandatory constraint here means that every A must play r1 (the Mandatory implies the subset).

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Role equality constraint

Also this quality constraint is implied, and should be removed.

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Implication

Who can explain the difference?

The two constraints in the first model says: each A must play r1 or r2 (or both), and that if A plays r2 then it must play r1. This means that r1 must be always played (which is the second model)

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Role Exclusion Constraint

Exclusion constraint:Every Employee is allocated a ParkingSpace should not claim MoneyAmt.

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Role Exclusion Constraint

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Role Exclusion Constraint

Each partner must be either a husband or wife (but not both at the same time).

Called “Exclusive-or”

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Exclusive-or (another example)

Each Account must be OwnedBy a Person or a Company, but not both.

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Role Exclusion Constraint

Each person has at most one of three vices. i.e., from 0 to 3 vices.

It can be written also as

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Pair Exclusion Constraint

How can we restrict that a person can drive a car only if he owns that car.

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Pair-subset constraint

An example of a tuple-subset constraint between sequences of three roles.

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Equality Constraint

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Pair Exclusion Constraint

Same person can ‘own’ and ‘wants to buy’ the same car?

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What is Wrong?

Implies

ImpliesImplies

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Outline

• Quick Math background

• Value Constraints

• Set Constrains

o Subset

o Equality

o Exclusion

• Subtype relations

• Frequency constraints

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Subtypes

Person

Male Female

• Generalization/Specialization hierarchy.• Subtype inherits the properties of its supertype.

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Subtypes

Person

Australian Female

FemaleAustralian

*

* The indirect subtype connection is implied, so it should be omitted

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Subtypes

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Subtypes

Person

Male Female

There is no person that can be Male and Female at the same time.

Person

Male Female

Every person must be a Male or a female.

Every person must be either a Male or a Female

Person

Male Female

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Subtypes

What is Inherited?

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What is Wrong?

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Outline

• Quick Math background

• Value Constraints

• Set Constrains

o Subset

o Equality

o Exclusion

• Subtype relations

• Frequency constraints also called “Occurrence constraints”

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Frequency constraints

To indicate that each entry in a fact column must occur there exactly n times, the number n is written beside the role.

Each city in the first column must occur

three times.each drive kind in the Second column must appear there twice

A compound transaction is needed to initially populate this fact type requiring at least six facts to be added.

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Frequency constraints

Each member of pop(r) occurs there exactly n times.

n must be a positive integer.

A r

n

A r

1

A r

If n = 1, this is equivalent to a uniqueness constraint

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Compound Frequency Constraint

The values of (Year and City) must occur exactly three times

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Ranged Frequency Constraint

Examples of minimum and maximum frequency constraints.

Each name of Panl must occur at least 4 and at most 7 times. That is, each Expert must on 4 to 7 Panels

Each Expert can referee 5 papersEach Paper can be refereed by at least two Experts.

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Discussion

Summarize what you learned? And what you think about it?

Compare what you learned with EER and UML?

Questions & Suggestions?