it.unibo.cs.belief
Interface MassPotential

All Known Implementing Classes:

TreeMassPotential

public interface MassPotential

A generalization of a mass function. A mass potential m over θ is a function from 2^θ to [0,1]. The mass function corresponding to a mass potential can be obtained using the normalize() method.

Version:

0.1

Author:

Matteo Magnani

Method Summary

void	addEvidence(Proposition prop, double mass) Assigns some evidence (mass) to a proposition.
void	applyThreshold(double threshold) Deletes all mass assignments under the specified value.
void	condition(Proposition prop) Conditions this mass potential to a subset of the frame.
boolean	equals(java.lang.Object mp)
Proposition	getCore() Returns the intersection of all the proposition to which this mass potential assigns some mass.
double	getEvidence(Proposition prop) Returns the evidence assigned to a proposition so far.
java.util.Set	getFocalSets() Returns the set of propositions to whom some evidence has been assigned.
Frame	getFrame() Returns the set of all possible elementary events from which propositions are composed.
void	normalize() Transforms this mass potential into a mass function.
Proposition	pick(java.util.Random ran)
BeliefFunction	toBeliefFunction() Produces the belief function corresponding to this mass potential.
CommonalityFunction	toCommonalityFunction() Produces the commonality function corresponding to this mass potential.
PlausibilityFunction	toPlausibilityFunction() Produces the plausibility function corresponding to this mass potential.

Method Detail

equals

boolean equals(java.lang.Object mp)

Overrides:

equals in class java.lang.Object

addEvidence

void addEvidence(Proposition prop,
                 double mass)

Assigns some evidence (mass) to a proposition. If some mass has already been assigned to the same proposition, the new mass is added to the previous value. Mass potentials are not normalized, so it is not necessary to assign exactly one unit of mass. If A and B are two propositions, the assignments m1(A)=80, m1(B)=40 and m2(A)=3, m2(B)=1.5 correspond to the same mass function.

Parameters:

prop - the proposition to which the evidence is assigned

mass - the evidence assigned to the proposition

getEvidence

double getEvidence(Proposition prop)

Returns the evidence assigned to a proposition so far.

Parameters:

prop - the proposition we want to check

Returns:

the evidence assigned to the proposition

normalize

void normalize()

Transforms this mass potential into a mass function. A mass function m is a particular case of mass potential, where no mass is assigned to the empty set and the sum of all mass is equal to one. Because of numerical approximation the sum may not be exactly one.

getFocalSets

java.util.Set getFocalSets()

Returns the set of propositions to whom some evidence has been assigned. These propositions are usually called focal sets. After normalization (normalize()) the empty proposition is not returned by this method.

Returns:

the set of focal sets of this mass potential

getFrame

Frame getFrame()

Returns the set of all possible elementary events from which propositions are composed. This set is usually called a frame of discernment.

Returns:

the frame whose powerset is the domain of this mass potential

getCore

Proposition getCore()

Returns the intersection of all the proposition to which this mass potential assigns some mass.

Returns:

the core of the mass potential, i.e., the intersection of its focal sets.

condition

void condition(Proposition prop)

Conditions this mass potential to a subset of the frame. The new mass potential is obtained assuming that the proposition on which it has been conditioned is true.

Parameters:

prop - the proposition on which this mass potential is conditioned

applyThreshold

void applyThreshold(double threshold)

Deletes all mass assignments under the specified value.

Parameters:

threshold - the minimum value of mass that is retained

toBeliefFunction

BeliefFunction toBeliefFunction()

Produces the belief function corresponding to this mass potential.

Returns:

a belief function

toPlausibilityFunction

PlausibilityFunction toPlausibilityFunction()

Produces the plausibility function corresponding to this mass potential.

Returns:

a plausibility function

toCommonalityFunction

CommonalityFunction toCommonalityFunction()

Produces the commonality function corresponding to this mass potential.

Returns:

a commonality function

pick

Proposition pick(java.util.Random ran)