Two papers on networks of parallel language processors

Networks of parallel language processors form a special type of grammar systems where derivation steps in the mode of L systems and communication steps alternate. Hitherto only networks have been considered where the underlying graph is the complete graph. In this paper we consider networks of parallel languages where the underlying graph is a star or a grid or a ring which are very common structures in network theory. We show that these graphs have the same power as the complete graph. (orig.)Available from TIB Hannover: RR 4485(1998,8) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Evolution and grammars

SIGLEAvailable from TIB Hannover: RR 4485(2000,9) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Chain-code pictures and collages generated by hyperedge replacement

Regular chain-code picture languages can be generated by collage grammars. As a consequence, all undecidability results known for regular chain-code languages can be adapted to picture languages generated by collage grammars. (orig.)Available from TIB Hannover: RR 4485(1995,3) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

3. International workshop on descriptional complexity of automata, grammars and related structures Preproceedings

SIGLEAvailable from TIB Hannover: RR 4485(2001,16) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Parallel communicating grammar systems as Language analyzers

Parallel communicating grammar systems consist of several grammars and perform derivation steps, where each of the grammars works in a parallel and synchronized manner on its own sentential form, and communication steps, where a transfer of sentential forms is done. We discuss accepting and analyzing versions of such grammar systems with context-free productions. In accepting parallel communicating grammar systems rules of the form #alpha##->#A with a word #alpha# and a nonterminal A are applied as in the generating case, and the language consists of all terminal words which can derive the axiom. We consider the usual variant and a restricted variant of accepting parallel communicating grammar systems and prove that all types of these accepting grammar systems characterize the family of recursively enumerable languages, if the usual variant is considered, and that of context-free languages, if the restricted one is used. The first result also holds if #lambda# rules are forbidden. Moreover, we study analyzing parallel communicating grammar systems the derivations of which perform the generating counterparts backwards. This requires a modification of the concept of generating derivation yielding to strong-returning parallel communicating grammar systems which also generate the family of recursively numerable languages. (orig.)SIGLEAvailable from TIB Hannover: RR 4485(1999,18) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman