ai.krr.fol
Class Instantiation

java.lang.Object
  ai.krr.fol.Instantiation

All Implemented Interfaces:

Substitution

public class Instantiation
extends java.lang.Object
implements Substitution

An Instantiation maps a set of Variables to a set of Terms. The resulting mapping need not be one-to-one, i.e. several Variables may be mapped to the same Variable.

Author:

Gerhard Wickler

Constructor Summary

Instantiation()

Method Summary

boolean	contains(Variable var) This function tests whether this Substitution maps the given Variable to a new Term.
Term	getValue(Variable aVar) This function returns the Term the given Variable is mapped to.
int	size() This function returns the number of variables bound by this Grounding.
boolean	unify(Term aTerm, Variable aVar) This function attempts to extend this Substitution such that the given Variable (from the "right" expression) and the given Term (from the "left") are unified and returns whether this succeeded.
boolean	unify(Variable aVar, Term aTerm) This function attempts to extend this Substitution such that the given Variable (from the "left" expression) and the given Term (from the "right") are unified and returns whether this succeeded.
boolean	unify(Variable leftVar, Variable rightVar) This function attempts to extend this Substitution such that the given Variables will be unified and returns true if this was possible.

Methods inherited from class java.lang.Object

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

Constructor Detail

Instantiation

public Instantiation()

Method Detail

size

public int size()

This function returns the number of variables bound by this Grounding.

Returns:

the number of mappings in this Grounding

unify

public boolean unify(Variable aVar,
                     Term aTerm)

This function attempts to extend this Substitution such that the given Variable (from the "left" expression) and the given Term (from the "right") are unified and returns whether this succeeded. This can only succeed if the given Term is a Constant or a Variable.

Specified by:

unify in interface Substitution

Parameters:

aVar - the Variable the given Term is to be unified with

aTerm - the Term the given Variable will be mapped to

Returns:

whether successful extension of this Substitution was possible

unify

public boolean unify(Term aTerm,
                     Variable aVar)

This function attempts to extend this Substitution such that the given Variable (from the "right" expression) and the given Term (from the "left") are unified and returns whether this succeeded. This can only succeed if the given Term is a Variable.

Specified by:

unify in interface Substitution

Parameters:

aTerm - the Term the given Variable will be mapped to

aVar - the Variable the given Term is to be unified with

Returns:

whether successful extension of this Substitution was possible

unify

public boolean unify(Variable leftVar,
                     Variable rightVar)

This function attempts to extend this Substitution such that the given Variables will be unified and returns true if this was possible. Where this matters, the first variable is considered to come from the "left" expression and the second from the "right".

Specified by:

unify in interface Substitution

Parameters:

leftVar - a Variable to be associated with the other given Variable

rightVar - a Variable to be associated with the other given Variable

Returns:

whether successful extension of this Substitution was possible

contains

public boolean contains(Variable var)

This function tests whether this Substitution maps the given Variable to a new Term.

Specified by:

contains in interface Substitution

Parameters:

var - the Variable the Term is being sought for

Returns:

whether an associated Term exists in this Substitution

getValue

public Term getValue(Variable aVar)

This function returns the Term the given Variable is mapped to. More specifically, it returns:

• a new VarTerm with a new Variable iff the Variable is not part of the Substitution or has no Term associated with it; the new VarTerm will be retained for future consistency;
• a Term that is the instantiation of the associated Term under this Substitution iff there is an associated term;

The given Variable is assumed to occur in the left Term.

Specified by:

getValue in interface Substitution

Parameters:

aVar - the Variable the Term is being sought for

Returns:

the instantiated Term the given Variable is mapped to