Languages Defined by Indian Parallel Systems

A special kind of parallel systems, namely Indian parallel systems, is studied. In the context-independent case the application of homomorphisms on sentential form languages is found to be more powerful than the use of a terminal subalphabet, both for systems with one or finitely many tables. Especially, the language family obtained by systems with one table using a terminal subalphabet is (nearly) an Anti-AFL. The effect of having at most one or finitely many axioms, erasing in the productions, and of applying codings, weak codings, non-erasing or arbitrary homomorphisms is considered, and a (not yet) complete hierarchy is presented, including also the relations to the context-free and ETOL-languages. Some results in the context-dependent case are given too.