Renaming and erasing in szilard languages

  • Matthias Höpner
  • Manfred Opp
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 52)


We characterize the images of Szilard languages under alphabetical homomorphisms using so called label grammars and show: If L is a label language (i.e. a language generated by such grammar) then L -{λ} is a coding (renaming) of some Szilard language. This result shows that arbitrary homomorphisms do not have more generating power than nonerasing ones except that they generate the empty word. Combining this result with other properties of label languages, established elsewhere, one obtains characterizations of label languages and of codings of Szilard languages including those by finite shuffle expressions and equations.

Since one might interprete label grammars as a special kind of labelled Petri nets, where each transition has exactly one input arc, we solved the elemination problem of λ-transitions for this restricted class of Petri nets, even if there occur infinite firing-sequences using only λ-transitions within a net.


Normal Derivation Normal Sequence Restricted Class Empty Word Sentential Form 
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    M.Höpner/M.Opp ‘Renaming and erasing in Szilard languages', Inst. f. Informatik, Univ. Hamburg, to be published.Google Scholar
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Copyright information

© Springer-Verlag Berlin Heidelberg 1977

Authors and Affiliations

  • Matthias Höpner
    • 1
  • Manfred Opp
    • 1
  1. 1.Institut f. InformatikUniv. HamburgHamburg 13

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