public boolean addAvf(OwlClass targetClass){
  targetClass.addAvfRestriction(this);
  return avfClasses.add(targetClass);
}

public boolean addAvf ( OwlClass targetClass ) { targetClass . addAvfRestriction ( this ) ; return avfClasses . add ( targetClass ) ; }
add " allvaluesfrom c " information , and tell c to point back here .
