  In this paper we propose a simple and efficient strategy to obtain a data
structure generator to accomplish a perfect hash of quite general order
restricted multidimensional arrays named {\em phormas}. The constructor of such
objects gets two parameters as input: an n-vector a of non negative integers
and a boolean function B on the types of order restrictions on the coordinates
of the valid n-vectors bounded by a. At compiler time, the phorma constructor
builds, from the pair a,B, a digraph G(a,B) with a single source s and a single
sink t such that the st-paths are in 1-1 correspondence with the members of the
B-restricted a-bounded array A(a,B). Besides perfectly hashing A(a,B), G(a,B)
is an instance of an NW-family. This permits other useful computational tasks
on it.
