A new method for description of molecular networks and packings is proposed and implemented into the program package TOPOS. It is shown that the method is most effective in combination with the multilevel analysis of intermolecular interactions in terms of molecular Voronoi polyhedra. The method was applied to 82 1,2-benzothiazine derivatives, 11 of which we have synthesized for the first time. As a result, we have determined the main transformation routes of underlying nets, i.e. the nets of molecular centroids, at different levels of van der Waals interaction and found the most important topologies that play a key role in these routes. The method can help to create databases of topological properties of molecular packing (second-level databases) from crystallographic databases (first-level databases); this is an important step to develop predictable expert systems in materials science.