code: @Override
  	protected Constraint[] createInternalConstraints(Variable from, Variable to) {		
  		this.xConstraint.setFrom(((RectangularRegion)from).getInternalVariables()[0]);
  		this.xConstraint.setTo(((RectangularRegion)to).getInternalVariables()[0]);
  		this.yConstraint.setFrom(((RectangularRegion)from).getInternalVariables()[1]);
  		this.yConstraint.setTo(((RectangularRegion)to).getInternalVariables()[1]);
  		//xConstraint should not be processed by Y solver		
  		xConstraint.skipSolver(((MultiVariable)from).getInternalConstraintSolvers()[1]);
  		//yConstraint should not be processed by X solver
  		yConstraint.skipSolver(((MultiVariable)from).getInternalConstraintSolvers()[0]);
  		return new Constraint[] {this.xConstraint, this.yConstraint};
  	}
docs: 3 by 3 composition Table