sjm.engine
Class ConsultingStructure

java.lang.Object
  |
  +--sjm.engine.Structure
        |
        +--sjm.engine.ConsultingStructure

public class ConsultingStructure

extends Structure

A ConsultingStructure is structure that can prove itself against an axiom source supplied with the constructor.

When a rule creates a dynamic version of itself, a normal structure will create a ConsultingStructure counterpart that uses the rule's scope, and that consults a given axiom source (such as a Program).

The primary behavior that a ConsultingStructure adds is the ability to prove itself.

Field Summary

protected AxiomEnumeration	axioms
protected Unification	currentUnification
protected DynamicRule	resolvent
protected AxiomSource	source

Fields inherited from class sjm.engine.Structure

emptyList, functor, terms

Constructor Summary

protected

ConsultingStructure(AxiomSource source, java.lang.Object functor, Term[] terms)

Method Summary

protected AxiomEnumeration	axioms()
boolean	canFindNextProof() Tests if this structure can find another proof, and, if so, sets this structure's variables to the values that make the proof true.
protected boolean	canUnify() Return true if this structure can unify with another rule in the program.
protected void	unbind() Release the variable bindings that the last unification produced.

Methods inherited from class sjm.engine.Structure

arity, copyForProof, equals, eval, functorAndArityEquals, headAndTail, isList, list, list, list, listTailString, listTermsToString, terms, toString, unify, unify, unify, variables

Methods inherited from class java.lang.Object

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

Field Detail

source

protected AxiomSource source

axioms

protected AxiomEnumeration axioms

currentUnification

protected Unification currentUnification

resolvent

protected DynamicRule resolvent

Constructor Detail

ConsultingStructure

protected ConsultingStructure(AxiomSource source,
                              java.lang.Object functor,
                              Term[] terms)

Method Detail

axioms

protected AxiomEnumeration axioms()

canFindNextProof

public boolean canFindNextProof()

Tests if this structure can find another proof, and, if so, sets this structure's variables to the values that make the proof true.

Overrides:

canFindNextProof in class Structure

Returns:

true if this structure can find another proof.

canUnify

protected boolean canUnify()

Return true if this structure can unify with another rule in the program.

A consulting structure proves itself true by unifying with the head of a rule in a program, and then asking the tail of that rule to prove itself. Unification is a kind of matching. Two structures unify if they have equal functors, and the terms all unify. A variable unifies with a structure simply by setting its instantiation to be the structure.

For example, the following structures can unify:

     starred(jamesCagney, Title, Year)
     starred(jamesCagney, "Yankee Doodle Dandy", 1942)
 

When these structures unify, the variable Title will bind itself to "Yankee Doodle Dandy", and Year will bind to 1942. To be more specific, Title will bind to the atom whose functor is "Yankee Doodle Dandy". Year will bind to the atom whose functor is the number 1942.

Returns:

true, if this structure can unify with an axiom in the axiom source

unbind

protected void unbind()

Release the variable bindings that the last unification produced.