burlap.mdp.core.oo.propositional

Class PropositionalFunction

java.lang.Object

burlap.mdp.core.oo.propositional.PropositionalFunction

Direct Known Subclasses:

BlockDude.AtExitPF, BlockDude.HoldingBlockPF, BlocksWorld.ClearPF, BlocksWorld.ColorPF, BlocksWorld.OnBlockPF, BlocksWorld.OnTablePF, FrostbiteDomain.IglooBuiltPF, FrostbiteDomain.InWaterPF, FrostbiteDomain.OnIcePF, FrostbiteDomain.OnPlatformPF, FrostbiteDomain.PlatformActivePF, GridWorldDomain.AtLocationPF, GridWorldDomain.WallToPF, LunarLanderDomain.OnPadPF, LunarLanderDomain.TouchGroundPF, LunarLanderDomain.TouchPadPF, LunarLanderDomain.TouchSurfacePF

public abstract class PropositionalFunction
extends java.lang.Object

The propositional function class defines evaluations of object instances in an OO-MDP state and are part of the definition for an OO-MDP domain. Propositional functions have an name to identify them and a set of typed parameters that they can take. Implementing this class requires implementing the abstract method isTrue(OOState, String...), which takes an input state, identifiers to one or more objects in the state, and returns true or false depending on whether the relationship of the object arguments this propositional function evaluates are satisfied.

If you want to determine all possible parameter bindings on which a PropositionalFunction's isTrue(OOState, String...) method can be evaluated, use the allGroundings(OOState) method, which takes as input an OOState, and detemrines which combinations of objects in the state can be applied to this object's typed parameters. The returned list will be a list of GroundedProp objects, where each GroundedProp object contains a reference to this PropositionalFunction and a list of the object reference on which to evaluate it. Similarly, if you want all possible groundings for a list of different PropositionalFunction objects, you can use the static allGroundingsFromList(List, OOState) method, which calls the allGroundings(OOState) method on each of the PropositionalFunction objects in the list, and concatenates their results into a single List of GroundedProp objects.

Optionally, the parameters of a propositional function may also be assigned to order groups that indicate any symmetry in the evaluation of the propositional function. For example, suppose we were to define a "touching" propositional function that specified whether two objects of a class representing blocks (called BLOCK) were touching in the world or not. Consider then, evaluating touching(block0, block1). Note that there is a symmetry in this evaluation; that is, touching(block0, block1) = touching(block1, block0) in which case there is no point to evaluate both argument orders, because evaluating one tells you the value of hte other. Specifying parameter order groups allows the designer to indicate these kinds of symmetry. If two parameters are set to the same order group, then it indicates that the evaluation for the propositional function will be the same for any order of parameters within that order group. If the order group between two parameters is different, then it indicates that the order of the parameters can change the result of the evaluation. So, in the previous touching example, if the parameter order groups of the two parameters were both "p0", then it indicates that touching(block0, block1) = touching(block1, block0); if one parameter was assigned to order group "p0" and the other to "p1", then it is possible that touching(block0, block1) != touching(block1, block0). If the parameter order groups of parameters are not specified, then they are all assumed to be different. Any specified parameter order groups will be checked in the allGroundings(OOState) method, so that different groundings that necessarily have the same value will only have one of the groundings included in the returned list.

Author:

James MacGlashan

Field Summary

Fields

Modifier and Type	Field and Description
protected java.lang.String	name
protected java.lang.String[]	parameterClasses
protected java.lang.String[]	parameterOrderGroup

Constructor Summary

Constructors

Constructor and Description
PropositionalFunction(java.lang.String name, java.lang.String[] parameterClasses) Initializes a propositional function with the given name and parameter object classes.
PropositionalFunction(java.lang.String name, java.lang.String[] parameterClasses, java.lang.String[] parameterOrderGroup) Initializes a propositional function with the given name, parameter object classes, and the parameter order groups of the parameters.

Method Summary

Modifier and Type	Method and Description
java.util.List<GroundedProp>	allGroundings(OOState s) Returns all possible groundings of this PropositionalFunction for the given State
static java.util.List<GroundedProp>	allGroundingsFromList(java.util.List<PropositionalFunction> pfs, OOState s) Returns all possible groundings for all of the PropositionalFunctions in the provided list for the given State.
boolean	equals(java.lang.Object obj)
static PropositionalFunction	findPF(java.util.List<PropositionalFunction> pfs, java.lang.String pfName) Used to retrieve a PropositionalFunction with a specified name from a list of them.
java.lang.String	getName() Returns the name of this propositional function.
java.lang.String[]	getParameterClasses() Returns the object classes of the parameters for this propositional function
java.lang.String[]	getParameterOrderGroups() Returns the parameter order group names for the parameters of this propositional function.
int	hashCode()
protected void	init(java.lang.String name, java.lang.String[] parameterClasses, java.lang.String[] parameterOrderGroup)
abstract boolean	isTrue(OOState s, java.lang.String... params) Returns whether the propositional function is true for the given state with the given parameters This version is preferred to the comma delimited version.
boolean	someGroundingIsTrue(OOState s) Returns true if there existing a GroundedProp for the provided State that is in true in the State.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

name

protected java.lang.String name

parameterClasses

protected java.lang.String[] parameterClasses

parameterOrderGroup

protected java.lang.String[] parameterOrderGroup

Constructor Detail

PropositionalFunction

public PropositionalFunction(java.lang.String name,
                             java.lang.String[] parameterClasses)

Initializes a propositional function with the given name and parameter object classes. Unique parameter order groups for each parameter are assumed; that is, the order of parameters always matters.

Parameters:

name - the name of the propositional function

parameterClasses - an array of strings specifying the name of object classes that the parameters must satisfy.

PropositionalFunction

public PropositionalFunction(java.lang.String name,
                             java.lang.String[] parameterClasses,
                             java.lang.String[] parameterOrderGroup)

Initializes a propositional function with the given name, parameter object classes, and the parameter order groups of the parameters.

Parameters:

name - the name of the propositional function

parameterClasses - an array of strings specifying the name of object classes that the parameters must satisfy.

parameterOrderGroup - an array of strings specifying order group names for the parameters

Method Detail

init

protected final void init(java.lang.String name,
                          java.lang.String[] parameterClasses,
                          java.lang.String[] parameterOrderGroup)

getName

public final java.lang.String getName()

Returns the name of this propositional function.

Returns:

the name of this propositional function.

getParameterClasses

public final java.lang.String[] getParameterClasses()

Returns the object classes of the parameters for this propositional function

Returns:

the object classes of the parameters for this propositional function

getParameterOrderGroups

public final java.lang.String[] getParameterOrderGroups()

Returns the parameter order group names for the parameters of this propositional function.

Returns:

the parameter order group names for the parameters of this propositional function.

isTrue

public abstract boolean isTrue(OOState s,
                               java.lang.String... params)

Returns whether the propositional function is true for the given state with the given parameters This version is preferred to the comma delimited version.

Parameters:

s - the state that is being checked

params - the parameters being passed in to the propositional function

Returns:

whether the propositional function is true

allGroundings

public java.util.List<GroundedProp> allGroundings(OOState s)

Returns all possible groundings of this PropositionalFunction for the given State

Parameters:

s - the State in which all groundings will be returned

Returns:

a List of all possible groundings of this PropositionalFunction for the given State

someGroundingIsTrue

public boolean someGroundingIsTrue(OOState s)

Returns true if there existing a GroundedProp for the provided State that is in true in the State.

Parameters:

s - the State to test.

Returns:

true if there existing a GroundedProp for the provided State that is in true in the State; false otherwise.

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

allGroundingsFromList

public static java.util.List<GroundedProp> allGroundingsFromList(java.util.List<PropositionalFunction> pfs,
                                                                 OOState s)

Returns all possible groundings for all of the PropositionalFunctions in the provided list for the given State.

Parameters:

pfs - The list of PropositionalFunctions for which all groundings will be returned.

s - the State in which the groundings should be produced.

Returns:

a List of all possible groundings for all of the PropositionalFunctions in the provided list for the given State

findPF

public static PropositionalFunction findPF(java.util.List<PropositionalFunction> pfs,
                                           java.lang.String pfName)

Used to retrieve a PropositionalFunction with a specified name from a list of them.

Parameters:

pfs - The list of PropositionalFunction objects to search.

pfName - The name of the PropositionalFunction

Returns:

the PropositionalFunction with the name or null if it does not exist