Examples of aima.core.logic.fol.Unifier

aima.core.logic.fol.Unifier

Artificial Intelligence A Modern Approach (3rd Edition): Figure 9.1, page 328.

 function UNIFY(x, y, theta) returns a substitution to make x and y identical inputs: x, a variable, constant, list, or compound y, a variable, constant, list, or compound theta, the substitution built up so far (optional, defaults to empty) if theta = failure then return failure else if x = y the return theta else if VARIABLE?(x) then return UNIVY-VAR(x, y, theta) else if VARIABLE?(y) then return UNIFY-VAR(y, x, theta) else if COMPOUND?(x) and COMPOUND?(y) then return UNIFY(x.ARGS, y.ARGS, UNIFY(x.OP, y.OP, theta)) else if LIST?(x) and LIST?(y) then return UNIFY(x.REST, y.REST, UNIFY(x.FIRST, y.FIRST, theta)) else return failure --------------------------------------------------------------------------------------------------- function UNIFY-VAR(var, x, theta) returns a substitution if {var/val} E theta then return UNIFY(val, x, theta) else if {x/val} E theta then return UNIFY(var, val, theta) else if OCCUR-CHECK?(var, x) then return failure else return add {var/x} to theta

Figure 9.1 The unification algorithm. The algorithm works by comparing the structures of the inputs, elements by element. The substitution theta that is the argument to UNIFY is built up along the way and is used to make sure that later comparisons are consistent with bindings that were established earlier. In a compound expression, such as F(A, B), the OP field picks out the function symbol F and the ARGS field picks out the argument list (A, B). @author Ciaran O'Reilly @author Ravi Mohan @author Mike Stampone

    this(domain, new FOLOTTERLikeTheoremProver());
  }


  public FOLKnowledgeBase(FOLDomain domain,
      InferenceProcedure inferenceProcedure) {
    this(domain, inferenceProcedure, new Unifier());
  }

    fOL_ModelEliminationDemo();
  }


  private static void unifierDemo() {
    FOLParser parser = new FOLParser(DomainFactory.knowsDomain());
    Unifier unifier = new Unifier();
    Map<Variable, Term> theta = new Hashtable<Variable, Term>();


    Sentence query = parser.parse("Knows(John,x)");
    Sentence johnKnowsJane = parser.parse("Knows(y,Mother(y))");


    System.out.println("------------");
    System.out.println("Unifier Demo");
    System.out.println("------------");
    Map<Variable, Term> subst = unifier.unify(query, johnKnowsJane, theta);
    System.out.println("Unify '" + query + "' with '" + johnKnowsJane
        + "' to get the substitution " + subst + ".");
    System.out.println("");
  }

    this(domain, new FOLOTTERLikeTheoremProver());
  }


  public FOLKnowledgeBase(FOLDomain domain,
      InferenceProcedure inferenceProcedure) {
    this(domain, inferenceProcedure, new Unifier());
  }

  private Map<Variable, Term> theta;


  @Before
  public void setUp() {
    parser = new FOLParser(DomainFactory.knowsDomain());
    unifier = new Unifier();
    theta = new Hashtable<Variable, Term>();
  }

Examples of aima.core.logic.fol.Unifier

Related Classes of aima.core.logic.fol.Unifier