ai.planning.propositional
Class Action

java.lang.Object
  ai.planning.propositional.Action

All Implemented Interfaces:

Action<ai.krr.propositions.Atom>

public class Action
extends java.lang.Object
implements Action<ai.krr.propositions.Atom>

An Action is an activity that may be executable by some agent. Every Action must be an instance of some ActionType. In propositional planning the only distinction between an Action and the ActionType it instantiates is the unique label that may be given to an Action. This can be used to distinguish multiple occurrences of Actions of the same ActionType in a plan, for example.

Author:

Gerhard Wickler

Field Summary

protected ai.krr.NamedSymbol	label the unique label for this Action or null
protected ActionType	type the ActionType which this Action instantiates

Constructor Summary

Action(ActionType type)
This constructor creates a new Action of the given type.

Method Summary

WorldState	applyIn(WorldState<ai.krr.propositions.Atom> state) This function computes a new WorldState that is the result of applying this Action in the given state.
protected Action	clone() This class does not support cloning and an Exception will be thrown if this method is called.
boolean	equals(java.lang.Object obj) This function compares this Action to the given Object which must be an Action.
ActionType	getActionType() This function returns the ActionType of this Action.
ai.krr.NamedSymbol	getLabel() This function returns the unique label that distinguishes this Action from other Actions of the same ActionType.
int	hashCode() This function returns a hash value for this action.
boolean	isApplicableIn(WorldState<ai.krr.propositions.Atom> state) This function tests whether this Action is applicable in the given state.
void	setLabel(ai.krr.NamedSymbol label) This function sets the unique label for this Action.
java.lang.String	toString() This function creates a String representation for this ActionType.

Methods inherited from class java.lang.Object

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

Field Detail

label

protected ai.krr.NamedSymbol label

the unique label for this Action or null

type

protected final ActionType type

the ActionType which this Action instantiates

Constructor Detail

Action

public Action(ActionType type)

This constructor creates a new Action of the given type. The Action is not given a unique label at this point.

Parameters:

type - the ActionType which this Action instantiates

Method Detail

clone

protected Action clone()
                throws java.lang.CloneNotSupportedException

This class does not support cloning and an Exception will be thrown if this method is called.

Overrides:

clone in class java.lang.Object

Returns:

nothing

Throws:

java.lang.CloneNotSupportedException - will be thrown

getActionType

public final ActionType getActionType()

This function returns the ActionType of this Action.

Specified by:

getActionType in interface Action<ai.krr.propositions.Atom>

Returns:

the ActionType instantiated by this Action

isApplicableIn

public boolean isApplicableIn(WorldState<ai.krr.propositions.Atom> state)

This function tests whether this Action is applicable in the given state. It returns true iff all the Action's preconditions are satisfied in the given WolrdState.

Specified by:

isApplicableIn in interface Action<ai.krr.propositions.Atom>

Parameters:

state - the WorldState in which applicability is to be tested

Returns:

whether applying this Action in the given state results in a well-defined state

applyIn

public WorldState applyIn(WorldState<ai.krr.propositions.Atom> state)

This function computes a new WorldState that is the result of applying this Action in the given state. The Action should be applicable or the result of this function may not be as expected. If assertions are switched on, applicability will be tested. The resulting WorldState is computed by first removing all the negative effects of the given Action from this state and then adding all the positive effects.

Specified by:

applyIn in interface Action<ai.krr.propositions.Atom>

Parameters:

state - the WorldState in which this Action to be applied

Returns:

a new WorldState that is the result of the state transition function applied to the WorldState

setLabel

public void setLabel(ai.krr.NamedSymbol label)

This function sets the unique label for this Action. Note that no test for uniqueness is performed here. Once a label has been assigned to an Action it should not be changed.

Parameters:

label - the label to be assigned to this Action

getLabel

public ai.krr.NamedSymbol getLabel()

This function returns the unique label that distinguishes this Action from other Actions of the same ActionType.

Returns:

the unique label of this Action (may be null)

equals

public boolean equals(java.lang.Object obj)

This function compares this Action to the given Object which must be an Action. If either of the Actions has a label assigned, equality of the Actions is determined by the identity of the labels. Otherwise two Actions are equal iff they are the same Object in memory (using the == test). Note that two Actions that have the same label should also have the same ActionType.

Overrides:

equals in class java.lang.Object

Parameters:

obj - the Action to which this is compared

Returns:

whether the Actions are of the same Action

hashCode

public int hashCode()

This function returns a hash value for this action. If a label has been assigned to this Action the hash code of the label is returned. Otherwise the Object-level hashCode() is used.

Overrides:

hashCode in class java.lang.Object

Returns:

an integer that can be used for hashing

toString

public java.lang.String toString()

This function creates a String representation for this ActionType.

Overrides:

toString in class java.lang.Object

Returns:

the String representing this WorldState