Pregroup grammars with letter promotions

  • Authors:
  • Wojciech Buszkowski;Zhe Lin

  • Affiliations:
  • Adam Mickiewicz University in Poznań, Poland;Adam Mickiewicz University in Poznań, Poland

  • Venue:
  • LATA'10 Proceedings of the 4th international conference on Language and Automata Theory and Applications
  • Year:
  • 2010

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Abstract

We study pregroup grammars with letter promotions $p^{(m)}\Rightarrow q^{(n)}$. We show that the Letter Promotion Problem for pregroups is solvable in polynomial time, if the size of p(n) is counted as |n|+1. In Mater and Fix [11], the problem is shown to be NP-hard, but their proof assumes the binary (or decimal, etc.) representation of n in p(n), which seems less natural for applications. We reduce the problem to a graph-theoretic problem, which is subsequently reduced to the emptiness problem for context-free languages. As a consequence, the following problems are in P: the word problem for pregroups with letter promotions and the membership problem for pregroup grammars with letter promotions.