aima.core.logic.fol.inference

Class FOLFCAsk

java.lang.Object

aima.core.logic.fol.inference.FOLFCAsk

All Implemented Interfaces:

InferenceProcedure

public class FOLFCAsk
extends java.lang.Object
implements InferenceProcedure

Artificial Intelligence A Modern Approach (3rd Edition): Figure 9.3, page 332.

 function FOL-FC-ASK(KB, alpha) returns a substitution or false
   inputs: KB, the knowledge base, a set of first order definite clauses
           alpha, the query, an atomic sentence
   local variables: new, the new sentences inferred on each iteration
   
   repeat until new is empty
      new <- {}
      for each rule in KB do
          (p1 ˆ ... ˆ pn => q) <- STANDARDIZE-VARAIBLES(rule)
          for each theta such that SUBST(theta, p1 ˆ ... ˆ pn) = SUBST(theta, p'1 ˆ ... ˆ p'n)
                         for some p'1,...,p'n in KB
              q' <- SUBST(theta, q)
              if q' does not unify with some sentence already in KB or new then
                   add q' to new
                   theta <- UNIFY(q', alpha)
                   if theta is not fail then return theta
      add new to KB
   return false
 

Figure 9.3 A conceptually straightforward, but very inefficient forward-chaining algo- rithm. On each iteration, it adds to KB all the atomic sentences that can be inferred in one step from the implication sentences and the atomic sentences already in KB. The function STANDARDIZE-VARIABLES replaces all variables in its arguments with new ones that have not been used before.

Author:

Ciaran O'Reilly

Constructor Summary

Constructors

Constructor and Description
FOLFCAsk()

Method Summary

Modifier and Type	Method and Description
InferenceResult	ask(FOLKnowledgeBase KB, Sentence query) FOL-FC-ASK returns a substitution or false.

Methods inherited from class java.lang.Object

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

Constructor Detail

FOLFCAsk

public FOLFCAsk()

Method Detail

ask

public InferenceResult ask(FOLKnowledgeBase KB,
                           Sentence query)

FOL-FC-ASK returns a substitution or false.

Specified by:

ask in interface InferenceProcedure

Parameters:

KB - the knowledge base, a set of first order definite clauses

query - the query, an atomic sentence

Returns:

a substitution or false