Using Key Diagrams to Design and Construct Roman Geometric Mosaics?

The complexity shown by some geometrical patterns of Roman mosaics and the high quality of their realization lead to think that for such patterns, unlike scenes with human or animal figures, a model of the general pattern was certainly not sufficient to guide the setting up; in order to answer this question one is led to conjecture the existence of diagrams (key diagrams) with which the craftsman, by looking at them, is able to identify (and/or remember) the geometrical structure of a basic element of the general pattern, as well as a way for constructing it - and possibly the whole pavement - with his usual instruments. This hypothesis is applied to some patterns which were well spread over the Roman world. The present study aims at showing how a given key diagram can apply to varied patterns and, conversely, how the making of a given complex pattern can rely on several articulated key diagrams.