PC grammar systems with five context-free components generate all recursively enumerable languages

PC grammar systems with five context-free components generate all recursively enumerable languages

Grammar Systems as Language Analyzers and Recursively Enumerable Languages

We consider parallel communicating grammar systems which 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 and present ch...

On the Degree Complexity of Special Non-Context-Free Languages with Respect to PC Grammar Systems

When modeling natural languages, three languages are of special interest. In natural languages, there occur phenomena like multiple agreements, crossed agreements and replication. These aspects are represented by the three languages K1 = {abc |n ≥ 1}, K2 = {abcd |m,n ≥ 1} and K3 = {ww |w ∈ {a, b}}, respectively. In the present paper, we give parallel communicating grammar systems (PC grammar sy...

Equality sets for recursively enumerable languages

We consider shifted equality sets of the form EG(a, g1, g2) = {w | g1(w) = ag2(w)}, where g1 and g2 are nonerasing morphisms and a is a letter. We are interested in the family consisting of the languages h(EG(J)), where h is a coding and EG(J) is a shifted equality set. We prove several closure properties for this family. Moreover, we show that every every recursively enumerable language L ⊆ A∗...

Polynomial Generators of Recursively Enumerable Languages