org.aspic.inference
Class Constant

java.lang.Object
  org.aspic.inference.Element
      org.aspic.inference.Constant

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable

Direct Known Subclasses:

ConstantNumber, Term

public class Constant
extends Element
implements java.lang.Cloneable

A Constant is the simplest sub-class of Element. It encapsulates a functor that can be used to represent a prolog grounded atom.

Author:

mjs (matthew.south @ cancer.org.uk)

See Also:

Serialized Form

Constructor Summary

Constant()
Default Constructor.

Constant(java.lang.String functor)
Typical constructor.

Method Summary

Constant	apply(Substitution subs) Return copy of this Element with the substitution applied.
java.lang.Object	clone() An element is incompletely cloned.
boolean	equals(java.lang.Object o)
java.lang.String	getFunctor() Simple getter for functor.
int	hashCode()
java.lang.String	inspect() (idea from the Ruby prototype) inspect allows us to see a representation of the text expression that the object is based on.
boolean	isEqualModuloVariables(Element testClause) Check to see if this Element matches another, bar Variable names i.e.
boolean	isGrounded() Check for free variables
boolean	isUnifiable(Element toUnify) Return true if this Element can be unified with the passed Element.
Constant	negation() Get's the negation of this constant, a Term with functor "~", and parameters (functor).
java.lang.String	ruleTag() Used as the key in KnowledgeBase.rulesMap.
void	setFunctor(java.lang.String functor) Simple setter of functor.
Substitution	unify(Element toUnify, Substitution subs) Try to unify this Element with another Element, using passed substitution as a starting point.
void	write(KnowledgeWriter writer) Using the Visitor pattern, this method allows the details of an Element to be written in different ways.

Methods inherited from class org.aspic.inference.Element

getId, getKnowledgeBase, setId, setKnowledgeBase, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

Constant

public Constant()

Default Constructor.

Constant

public Constant(java.lang.String functor)

Typical constructor. A Constant needs a functor.

Parameters:

functor -

Method Detail

getFunctor

public java.lang.String getFunctor()

Simple getter for functor.

Returns:

constant's functor.

setFunctor

public void setFunctor(java.lang.String functor)

Simple setter of functor.

Parameters:

functor - new functor.

negation

public Constant negation()

Get's the negation of this constant, a Term with functor "~", and parameters (functor).

Returns:

Term representing negation of this Constant

inspect

public java.lang.String inspect()

Description copied from class: Element

(idea from the Ruby prototype) inspect allows us to see a representation of the text expression that the object is based on. Not implemented by overriding toString() because it's still useful to be able to inspect the objectID which toString returns.

Specified by:

inspect in class Element

Returns:

String representation of this knowledge atom

apply

public Constant apply(Substitution subs)

Description copied from class: Element

Return copy of this Element with the substitution applied.

Specified by:

apply in class Element

Parameters:

subs - Substitution to apply

Returns:

Copy of this Element with substitution applied to it.

isUnifiable

public boolean isUnifiable(Element toUnify)

Description copied from class: Element

Return true if this Element can be unified with the passed Element.

Specified by:

isUnifiable in class Element

Returns:

true iff testClause can be unified with the passed clause

unify

public Substitution unify(Element toUnify,
                          Substitution subs)

Description copied from class: Element

Try to unify this Element with another Element, using passed substitution as a starting point. If the clause is not unifiable (@see isUnifiable), subs is returned unaffected.

Specified by:

unify in class Element

Parameters:

toUnify - Element to be unified with this Element

subs - starting substitution

Returns:

Most General Unifier (MGU) as a Substitution object

isEqualModuloVariables

public boolean isEqualModuloVariables(Element testClause)

Description copied from class: Element

Check to see if this Element matches another, bar Variable names i.e. likes(john, X) isEqualModuloVariables to likes(john, Y).

Parameters:

testClause - Element to checked against this one.

Returns:

true iff testClause is the same as this Element, apart from Variable names.

isGrounded

public boolean isGrounded()

Description copied from class: Element

Check for free variables

Returns:

true iff this Element has no free variables

ruleTag

public java.lang.String ruleTag()

Used as the key in KnowledgeBase.rulesMap.

Returns:

a string that identifies this constant (or term).

write

public void write(KnowledgeWriter writer)

Description copied from class: Element

Using the Visitor pattern, this method allows the details of an Element to be written in different ways.

Specified by:

write in class Element

Parameters:

writer - the object that does the writing.

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

clone

public java.lang.Object clone()
                       throws java.lang.CloneNotSupportedException

Description copied from class: Element

An element is incompletely cloned. Everything except it's knowledgeBase reference is cloned.

Overrides:

clone in class Element

Throws:

java.lang.CloneNotSupportedException