14. The computer program product of claim 11 , wherein each approximation defines a lower bound d min and an upper bound d max , and the product further comprises: computer readable code means executable by a processor for generating a candidate set of approximations based at least on the lower bounds d min and upper bounds d max of the approximations.
14. The computer program product of claim 11 , wherein each approximation defines a lower bound d min and an upper bound d max , and the product further comprises: computer readable code means executable by a processor for generating a candidate set of approximations based at least on the lower bounds d min and upper bounds d max of the approximations. 15. The computer program product of claim 14 , wherein each approximation defines an upper bound d max , and the product further comprises: computer readable code means executable by a processor for generating a candidate set of approximations based at least on the upper bounds d max of the approximations.