ubc.cs.JLog.Foundation
Class jRule

java.lang.Object
  ubc.cs.JLog.Foundation.jRule

All Implemented Interfaces:

iConsultable, iName, iNameArity

Direct Known Subclasses:

jBuiltinRule

public class jRule
extends Object
implements iNameArity, iConsultable

This class represents a rule of the form Head :- Base, where Head is a predicate and Base is a term of predicates.

Version:

%I%, %G%

Author:

Glendon Holst

Field Summary

protected boolean	all_variables
protected jPredicateTerms	base
protected jPredicate	head
protected jVariableVector	variables

Constructor Summary

jRule(jPredicate h, jPredicateTerms b)

Method Summary

void	consult(jKnowledgeBase kb) Consult the given jKnowledgeBase and cache any invariant values (those which would not change until the next time the jKnowledgeBase changes).
void	consultReset() Called when the jKnowledgeBase changes.
Enumeration	enumBase()
int	getArity() Returns the arity of this instance.
jPredicateTerms	getBase()
jPredicate	getHead()
String	getName() Returns the name of this instance.
jTerm	getUnifiedBase(jCompoundTerm input_goal, jUnifiedVector unified) Test if rule head will unify.
boolean	isConsultNeeded() Determine if cached values already exist and hence if consulting is required.
String	toString()
boolean	unify(jPredicateGoal pg, iGoalStack goals)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

head

protected jPredicate head

base

protected jPredicateTerms base

variables

protected jVariableVector variables

all_variables

protected boolean all_variables

Constructor Detail

jRule

public jRule(jPredicate h,
             jPredicateTerms b)

Method Detail

getName

public String getName()

Description copied from interface: iName

Returns the name of this instance.

Specified by:

getName in interface iName

Returns:

String containing name of this instance.

getArity

public int getArity()

Description copied from interface: iNameArity

Returns the arity of this instance.

Specified by:

getArity in interface iNameArity

Returns:

int whose value is the arity of this instance.

getHead

public jPredicate getHead()

getBase

public jPredicateTerms getBase()

unify

public boolean unify(jPredicateGoal pg,
                     iGoalStack goals)

getUnifiedBase

public jTerm getUnifiedBase(jCompoundTerm input_goal,
                            jUnifiedVector unified)

Test if rule head will unify. Assumes predicate name and arity already match.

Returns:

The duplicated base jTerm if it head unifies, null otherwise.

consult

public void consult(jKnowledgeBase kb)

Description copied from interface: iConsultable

Consult the given jKnowledgeBase and cache any invariant values (those which would not change until the next time the jKnowledgeBase changes). Where possible, consultable objects should minimize computation and assume that any cached values are still accurate.

Specified by:

consult in interface iConsultable

Parameters:

kb - the knowledge base which attempted proofs are based upon.

consultReset

public void consultReset()

Description copied from interface: iConsultable

Called when the jKnowledgeBase changes. Should set all cached values to dirty so that a following call to consult would perform a full lookup as required.

Specified by:

consultReset in interface iConsultable

isConsultNeeded

public boolean isConsultNeeded()

Description copied from interface: iConsultable

Determine if cached values already exist and hence if consulting is required. If object does not knowimmediatly whether consulting is needed, then assuming it is required.

Specified by:

isConsultNeeded in interface iConsultable

Returns:

false if cached values are valid, true otherwise, if consult should be called.

enumBase

public Enumeration enumBase()

toString

public String toString()

Overrides:

toString in class Object