THE CODE PROBLEM FOR DIRECTED FIGURES

We consider directed figures defined as labelled polyominoeswith designated start and end points, with two types of catenationoperations. We are especially interested in codicity verification for setsof figures, and we show that depending on the catenation type thequestion whether a given set of directed figures is a code is decidableor not. In the former case we give a constructive proof which leads toa straightforward algorithm