aima.core.logic.fol.inference

Class FOLBCAsk

java.lang.Object

aima.core.logic.fol.inference.FOLBCAsk

All Implemented Interfaces:

InferenceProcedure

public class FOLBCAsk
extends java.lang.Object
implements InferenceProcedure

Artificial Intelligence A Modern Approach (2nd Edition): Figure 9.6, page 288.

 function FOL-BC-ASK(KB, goals, theta) returns a set of substitutions
   input: KB, a knowledge base
          goals, a list of conjuncts forming a query (theta already applied)
          theta, the current substitution, initially the empty substitution {}
   local variables: answers, a set of substitutions, initially empty
   
   if goals is empty then return {theta}
   qDelta <- SUBST(theta, FIRST(goals))
   for each sentence r in KB where STANDARDIZE-APART(r) = (p1 ˆ ... ˆ pn => q)
          and thetaDelta <- UNIFY(q, qDelta) succeeds
       new_goals <- [p1,...,pn|REST(goals)]
       answers <- FOL-BC-ASK(KB, new_goals, COMPOSE(thetaDelta, theta)) U answers
   return answers
 

Figure 9.6 A simple backward-chaining algorithm.

Author:

Ciaran O'Reilly, Mike Stampone

Constructor Summary

Constructors

Constructor and Description
FOLBCAsk()

Method Summary

Modifier and Type	Method and Description
InferenceResult	ask(FOLKnowledgeBase KB, Sentence query) Returns a set of substitutions

Methods inherited from class java.lang.Object

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

Constructor Detail

FOLBCAsk

public FOLBCAsk()

Method Detail

ask

public InferenceResult ask(FOLKnowledgeBase KB,
                           Sentence query)

Returns a set of substitutions

Specified by:

ask in interface InferenceProcedure

Parameters:

KB - a knowledge base

query - goals, a list of conjuncts forming a query

Returns:

a set of substitutions