ai.planning.strips
Class ModelBasedState

java.lang.Object
  ai.planning.strips.WorldState
      ai.planning.strips.ModelBasedState

All Implemented Interfaces:

WorldState<ai.krr.fol.Atom>, java.lang.Iterable<ai.krr.fol.Atom>

public class ModelBasedState
extends WorldState

A WorldState is a logical representation of all the facts that are true in the state of the world represented by this WorldState. In AI planning this is often called a situation. In the STRIPS representation a WorldState consists of the set of function-free, ground first-order Atoms that are true in the situation. Atoms not in the set are considered to be false, i.e. this representation assumes a closed world.

Author:

Gerhard Wickler

See Also:

Atom

Nested Class Summary

static interface	ModelBasedState.RelationModel
protected static class	ModelBasedState.SetModel

Nested classes/interfaces inherited from class ai.planning.strips.WorldState

WorldState.MetaIterator<E>, WorldState.NoElementIterator<E>

Field Summary

protected ModelBasedState.RelationModel[]	fluents the (fluent) relations that hold in this state (indexed by predicate)
protected ai.krr.NamedSymbol[]	fRelSys the array containing the fluent predicates (for indexing fluents)
protected java.util.Map<ai.krr.NamedSymbol,ModelBasedState.RelationModel>	statics the (static) relations that hold in all states (indexed by predicate)

Fields inherited from class ai.planning.strips.WorldState

domain, hashValue

Constructor Summary

ModelBasedState(java.util.Set<ai.krr.fol.Atom> atoms, Domain domain)
This constructor creates a new WorldState in which the given Atoms are true.

Method Summary

void	add(ai.krr.fol.Atom atom) This function asserts the given Atom in this WorldState.
ModelBasedState	clone() This function creates a copy of this WorldState.
boolean	entails(ai.krr.fol.Atom atom) This function tests whether the given Atom holds in this WorldState.
boolean	equals(ModelBasedState state)
boolean	equals(WorldState state) This function tests whether this and the given state are equal.
boolean	falsifies(ai.krr.fol.Atom atom) This function tests whether the given Atom does not hold in this WorldState.
ModelBasedState.RelationModel	getModel(ai.krr.NamedSymbol relation) This function retrieves all those Atoms that are true for the given (static or fluent) relation in this state.
java.util.Iterator<ai.krr.fol.Atom>	iterator() This function returns an Iterator that enumerates all the fluents that hold in this state.
java.util.Iterator<ai.krr.fol.Atom>	iterator(ai.krr.NamedSymbol relation) This function returns an Iterator that enumerates some of the fluents that hold in this state.
void	retract(ai.krr.fol.Atom atom) This function deletes the given Atom from this WorldState.
int	size() This function returns the number of different fluents that are holding in this state.
int	size(ai.krr.NamedSymbol relation) This function returns the number of atoms that are holding in this state for the given relation.
java.lang.String	toString() This function creates a String representation for this WorldState.

Methods inherited from class ai.planning.strips.WorldState

addAll, entailsAll, equals, getDomain, hashCode, retractAll

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

statics

protected java.util.Map<ai.krr.NamedSymbol,ModelBasedState.RelationModel> statics

the (static) relations that hold in all states (indexed by predicate)

fRelSys

protected ai.krr.NamedSymbol[] fRelSys

the array containing the fluent predicates (for indexing fluents)

fluents

protected ModelBasedState.RelationModel[] fluents

the (fluent) relations that hold in this state (indexed by predicate)

Constructor Detail

ModelBasedState

public ModelBasedState(java.util.Set<ai.krr.fol.Atom> atoms,
                       Domain domain)

This constructor creates a new WorldState in which the given Atoms are true. Static relations that hold must be added in this constructor.

Parameters:

atoms - the Atoms holding in this WorldState

domain - the Domain to which this WorldState refers

Method Detail

clone

public ModelBasedState clone()

This function creates a copy of this WorldState. Subsequent modifications will not change the original state.

Specified by:

clone in class WorldState

Returns:

a new WorldState in which the same Atoms hold (as in this state)

size

public int size()

This function returns the number of different fluents that are holding in this state.

Specified by:

size in interface WorldState<ai.krr.fol.Atom>

Specified by:

size in class WorldState

Returns:

number of true fluent atoms

size

public int size(ai.krr.NamedSymbol relation)

This function returns the number of atoms that are holding in this state for the given relation. The relation may be fluent or static.

Specified by:

size in class WorldState

Returns:

number of true fluent atoms

add

public void add(ai.krr.fol.Atom atom)

This function asserts the given Atom in this WorldState. Note that all static relations must be defined in the constructor and thus the given atom must be a fluent relation.

Specified by:

add in interface WorldState<ai.krr.fol.Atom>

Specified by:

add in class WorldState

Parameters:

atom - the Atom that is to hold in this state

retract

public void retract(ai.krr.fol.Atom atom)

This function deletes the given Atom from this WorldState. Note that the given Atom should be a fluent relation.

Specified by:

retract in interface WorldState<ai.krr.fol.Atom>

Specified by:

retract in class WorldState

Parameters:

atom - the Atom that is not to hold in this state

entails

public boolean entails(ai.krr.fol.Atom atom)

This function tests whether the given Atom holds in this WorldState.

Specified by:

entails in interface WorldState<ai.krr.fol.Atom>

Specified by:

entails in class WorldState

Parameters:

atom - the Atom that may or may not be true

Returns:

true iff the given Atom is a member of the set of Atoms representing this state

falsifies

public boolean falsifies(ai.krr.fol.Atom atom)

This function tests whether the given Atom does not hold in this WorldState.

Specified by:

falsifies in interface WorldState<ai.krr.fol.Atom>

Specified by:

falsifies in class WorldState

Parameters:

atom - the Atom that may or may not be true

Returns:

true iff the given Atom is not a member of the set of Atoms representing this state

iterator

public java.util.Iterator<ai.krr.fol.Atom> iterator()

This function returns an Iterator that enumerates all the fluents that hold in this state.

Specified by:

iterator in interface java.lang.Iterable<ai.krr.fol.Atom>

Specified by:

iterator in class WorldState

Returns:

an Iterator for Atoms that are entailed by this state

iterator

public java.util.Iterator<ai.krr.fol.Atom> iterator(ai.krr.NamedSymbol relation)

This function returns an Iterator that enumerates some of the fluents that hold in this state. The enumerated Atoms are exactly those that are related by the given relation.

Specified by:

iterator in class WorldState

Parameters:

relation - the relation for which Atoms should be enumerated

Returns:

an Iterator for Atoms that are entailed by this state

getModel

public ModelBasedState.RelationModel getModel(ai.krr.NamedSymbol relation)

This function retrieves all those Atoms that are true for the given (static or fluent) relation in this state.

Parameters:

relation - the relation that is sought

Returns:

all currently true Atoms for the given relation

equals

public boolean equals(WorldState state)

This function tests whether this and the given state are equal. It returns true iff the two states contain exactly the same fluents.

Overrides:

equals in class WorldState

Parameters:

obj - the Object this WorldState is compared to

Returns:

whether the same fluent Atoms hold in both states

equals

public boolean equals(ModelBasedState state)

toString

public java.lang.String toString()

This function creates a String representation for this WorldState. This is simply the String representing the contained Set of Atoms.

Overrides:

toString in class java.lang.Object

Returns:

the String representing this WorldState