Planograms

To allocate space to products within a retail display (a) a full master planogram is constructed to represent universal rules governing the relative positions of products, (b) a master planogram is constructed on each occasion that space re-allocation is required, the master planogram representing preferred product positions, (c) a sequence stack 22 is derived to identity those products present in the full master planogram and absent from the master planogram, and to associate each absent product with a present product, and (d) the sequence stack is used to reintroduce absent products into the master planogram, at positions dictated by associations recorded in the sequence stack, to produce a sequence table for space allocation in accordance with the rules embodied in the full master planogram and subject to the preferences expressed in the master planogram.