net.sf.tweety.logics.cl.semantics

Class RankingFunction

java.lang.Object

net.sf.tweety.commons.AbstractInterpretation<ClBeliefSet,Conditional>

net.sf.tweety.logics.cl.semantics.RankingFunction

All Implemented Interfaces:

Interpretation<ClBeliefSet,Conditional>

public class RankingFunction
extends AbstractInterpretation<ClBeliefSet,Conditional>

A ranking function (or ordinal conditional function, OCF) that maps possible worlds of a propositional language to integers.

See W. Spohn. Ordinal conditional functions: a dynamic theory of epistemic states. In W.L. Harper and B. Skyrms, editors, Causation in Decision, Belief Change, and Statistics, II, pages 105-134. Kluwer Academic Publishers, 1988.

Author:

Matthias Thimm

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.Integer	INFINITY Integer used to define infinity.
private java.util.Map<PossibleWorld,java.lang.Integer>	ranks The ranks of the possible worlds.
private PropositionalSignature	signature The signature of the language this ranking function is defined on.

Constructor Summary

Constructors

Constructor and Description
RankingFunction(PropositionalSignature signature) Creates a new ranking function mapping each given interpretation to zero.

Method Summary

Modifier and Type	Method and Description
boolean	equals(java.lang.Object other)
static boolean	falsifies(PossibleWorld w, Conditional c) Checks whether the given possible world w falsifies the given conditional (B|A), i.e.
void	forceStrictness(java.util.Set<PropositionalFormula> formulas) Sets the rank of every interpretation i that does not satisfy the given set of formulas to RankingFunction.INFINITY.
java.util.Set<PossibleWorld>	getPossibleWorlds() Returns all interpretations that are mapped to a rank unequal to INFINITY.
PropositionalSignature	getSignature() Returns the signature of the first-order language this ranking function is defined on.
boolean	isNormalized() Checkes whether this OCF is normalized, i.e.
private java.lang.Integer	minimalRank() Returns the minimal rank of this OCF.
void	normalize() Normalizes this OCF, i.e.
java.lang.Integer	rank(PossibleWorld w) Gets the rank of the given possible world.
java.lang.Integer	rank(PropositionalFormula formula) Gets the rank of the given formula.
boolean	satisfies(ClBeliefSet beliefBase) Checks whether this interpretation satisfies the given knowledge base.
boolean	satisfies(Conditional formula) Checks whether this interpretation satisfies the given formula.
static boolean	satisfies(PossibleWorld w, Conditional c) Checks whether the given possible world w satisfies the given conditional (B|A), i.e.
void	setRank(PossibleWorld w, java.lang.Integer value) Sets the rank for the given possible world.
java.lang.String	toString()
static boolean	verifies(PossibleWorld w, Conditional c) Checks whether the given possible world w verifies the given conditional (B|A), i.e.

Methods inherited from class net.sf.tweety.commons.AbstractInterpretation

satisfies

Methods inherited from class java.lang.Object

clone, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

INFINITY

public static final java.lang.Integer INFINITY

Integer used to define infinity.

ranks

private java.util.Map<PossibleWorld,java.lang.Integer> ranks

The ranks of the possible worlds.

signature

private PropositionalSignature signature

The signature of the language this ranking function is defined on.

Constructor Detail

RankingFunction

public RankingFunction(PropositionalSignature signature)

Creates a new ranking function mapping each given interpretation to zero.

Parameters:

signature - the signature of the language this ranking function is defined on.

Method Detail

rank

public java.lang.Integer rank(PossibleWorld w)
                       throws java.lang.IllegalArgumentException

Gets the rank of the given possible world.

Parameters:

w - an possible world.

Returns:

the rank of the given possible world.

Throws:

java.lang.IllegalArgumentException - if the given possible world has no rank in this ranking function.

setRank

public void setRank(PossibleWorld w,
                    java.lang.Integer value)

Sets the rank for the given possible world.

Parameters:

w - an possible world.

value - the rank for the possible world.

satisfies

public boolean satisfies(Conditional formula)
                  throws java.lang.IllegalArgumentException

Description copied from interface: Interpretation

Checks whether this interpretation satisfies the given formula.

Parameters:

formula - a formula .

Returns:

"true" if this interpretation satisfies the given formula.

Throws:

java.lang.IllegalArgumentException - if the formula does not correspond to the expected language.

satisfies

public boolean satisfies(ClBeliefSet beliefBase)

Description copied from interface: Interpretation

Checks whether this interpretation satisfies the given knowledge base.

Parameters:

beliefBase - a knowledge base.

Returns:

"true" if this interpretation satisfies the given knowledge base.

forceStrictness

public void forceStrictness(java.util.Set<PropositionalFormula> formulas)

Sets the rank of every interpretation i that does not satisfy the given set of formulas to RankingFunction.INFINITY.

Parameters:

formulas - a set of first-order formulas.

rank

public java.lang.Integer rank(PropositionalFormula formula)
                       throws java.lang.IllegalArgumentException

Gets the rank of the given formula. Throws an IllegalArgumentException when the language of the formula does not correspond to the language of the interpretations this ranking function is defined on. Otherwise the rank of a formula is defined as the minimal rank of its satisfying interpretations.

Parameters:

formula - a formula.

Returns:

the rank of the given formula.

Throws:

java.lang.IllegalArgumentException - if the languages of the formula does not correspond to the language of the interpretations this ranking function is defined on.

minimalRank

private java.lang.Integer minimalRank()

Returns the minimal rank of this OCF.

Returns:

the minimal rank of this OCF.

normalize

public void normalize()

Normalizes this OCF, i.e. appropriately shifts the ranks such that the minimal rank equals zero.

isNormalized

public boolean isNormalized()

Checkes whether this OCF is normalized, i.e. whether its minimal rank value is zero.

Returns:

"true" if this OCF is normalized

getPossibleWorlds

public java.util.Set<PossibleWorld> getPossibleWorlds()

Returns all interpretations that are mapped to a rank unequal to INFINITY.

Returns:

all interpretations that are mapped to a rank unequal to INFINITY.

getSignature

public PropositionalSignature getSignature()

Returns the signature of the first-order language this ranking function is defined on.

verifies

public static boolean verifies(PossibleWorld w,
                               Conditional c)

Checks whether the given possible world w verifies the given conditional (B|A), i.e. whether w satisfies A and B

Parameters:

w - a possible world

c - a conditional.

Returns:

"true" if the given possible world verifies the given conditional.

falsifies

public static boolean falsifies(PossibleWorld w,
                                Conditional c)

Checks whether the given possible world w falsifies the given conditional (B|A), i.e. whether w satisfies A and not B

Parameters:

w - a possible world

c - a conditional.

Returns:

"true" if the given possible world falsifies the given conditional.

satisfies

public static boolean satisfies(PossibleWorld w,
                                Conditional c)

Checks whether the given possible world w satisfies the given conditional (B|A), i.e. whether w does not falsify c.

Parameters:

w - a possible world

c - a conditional.

Returns:

"true" if the given possible world satisfies the given conditional.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

equals

public boolean equals(java.lang.Object other)

Overrides:

equals in class java.lang.Object