On a hierarchy of languages generated by cooperating distributed grammar systems

摘要

For cooperating distributed grammar systems working in =k-mode up to now it is only known that this mode can be simulated by the=k.e-code for e>1. In this note we show how to improve this simulation when a termination condition is additionally required, showing that the (t＾=k)-mode can be simulated by the (t＾=k＋1)-mode if the number of components in the underlying cooperating distributed grammar system is increased by two. A similar result is given for the (t＾≤k)-mode.