net.sf.tweety.logics.cl.semantics

Class RankingFunction

java.lang.Object

net.sf.tweety.commons.AbstractInterpretation

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

All Implemented Interfaces:

net.sf.tweety.commons.Interpretation

public class RankingFunction
extends net.sf.tweety.commons.AbstractInterpretation

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 Integer	INFINITY Integer used to define infinity.

Constructor Summary

Constructors

Constructor and Description
RankingFunction(net.sf.tweety.logics.pl.syntax.PropositionalSignature signature) Creates a new ranking function mapping each given interpretation to zero.

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object other)
static boolean	falsifies(net.sf.tweety.logics.pl.semantics.PossibleWorld w, Conditional c) Checks whether the given possible world w falsifies the given conditional (B|A), i.e.
void	forceStrictness(Set<net.sf.tweety.logics.pl.syntax.PropositionalFormula> formulas) Sets the rank of every interpretation i that does not satisfy the given set of formulas to RankingFunction.INFINITY.
Set<net.sf.tweety.logics.pl.semantics.PossibleWorld>	getPossibleWorlds() Returns all interpretations that are mapped to a rank unequal to INFINITY.
net.sf.tweety.logics.pl.syntax.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.
void	normalize() Normalizes this OCF, i.e.
Integer	rank(net.sf.tweety.commons.Formula formula) Gets the rank of the given formula.
Integer	rank(net.sf.tweety.logics.pl.semantics.PossibleWorld w) Gets the rank of the given possible world.
boolean	satisfies(net.sf.tweety.commons.BeliefBase beliefBase)
boolean	satisfies(net.sf.tweety.commons.Formula formula)
static boolean	satisfies(net.sf.tweety.logics.pl.semantics.PossibleWorld w, Conditional c) Checks whether the given possible world w satisfies the given conditional (B|A), i.e.
void	setRank(net.sf.tweety.logics.pl.semantics.PossibleWorld w, Integer value) Sets the rank for the given possible world.
String	toString()
static boolean	verifies(net.sf.tweety.logics.pl.semantics.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 Integer INFINITY

Integer used to define infinity.

Constructor Detail

RankingFunction

public RankingFunction(net.sf.tweety.logics.pl.syntax.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 Integer rank(net.sf.tweety.logics.pl.semantics.PossibleWorld w)
             throws IllegalArgumentException

Gets the rank of the given possible world.

Parameters:

w - an possible world.

Returns:

the rank of the given possible world.

Throws:

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

setRank

public void setRank(net.sf.tweety.logics.pl.semantics.PossibleWorld w,
                    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(net.sf.tweety.commons.Formula formula)
                  throws IllegalArgumentException

Throws:

IllegalArgumentException

satisfies

public boolean satisfies(net.sf.tweety.commons.BeliefBase beliefBase)

forceStrictness

public void forceStrictness(Set<net.sf.tweety.logics.pl.syntax.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 Integer rank(net.sf.tweety.commons.Formula formula)
             throws 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:

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

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 Set<net.sf.tweety.logics.pl.semantics.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 net.sf.tweety.logics.pl.syntax.PropositionalSignature getSignature()

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

verifies

public static boolean verifies(net.sf.tweety.logics.pl.semantics.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(net.sf.tweety.logics.pl.semantics.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(net.sf.tweety.logics.pl.semantics.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 String toString()

Overrides:

toString in class Object

equals

public boolean equals(Object other)

Overrides:

equals in class Object