Some necessary clarifications about the chords' problem and the Partial Digest Problem

We state in previous paper [A. Daurat, Y. Gérard, M. Nivat, The chords' problem, Theoret. Comput. Sci. 282(2) (2002) 319-336] that the chords' problem can be solved in polynomial time. This result is however ambiguous and some people have been abused because the encoding of the data has not been given. The correctness of the result requires to specify the encoding of the data that we have used and to highlight the difference with the usual encoding implicitly considered in Partial Digest Problem.