SE-systems, timing mechanisms, and time-varying codes

We show that synchronized extension systems [17] can be successfully used to simulate timing mechanisms incorporated into grammars and automata [3, 7-9, 12]. Further, we introduce the concept of a time-varying code as a natural generalization of L-codes, and the relationship with classical codes, gsm codes and SE-codes is established. Finally, an algorithm for testing the time-varying code property in case of periodicity is given.