CODES MODULO FINITE MONADIC STRING-REWRITING SYSTEMS

Otto, F. and P. Narendran, Codes modulo finite monadic string-rewriting systems, Theoretical Computer Science 134 (1994) 175-188. A set C subset-of SIGMA* is called a code modulo a string-rewriting system T if, for all upsilon1, upsilon2,..., upsilon(k), w1, w2, ..., w(m) is-an-element-ofC, upsilon1 upsilon2...upsilon(k) <-- -->T* w1 w2...w(m) implies that k = m and upsilon(i) = w(i), i = 1, ..., k. Here we show that it is decidable whether a regular set is a code modulo T, when T is a finite string-rewriting system that is monadic and confluent, or that is special and lambda-confluent.