Picture languages: tiling systems versus tile rewriting grammars

  • Authors:
  • Alessandra Cherubini;Stefano Crespi Reghizzi;Matteo Pradella;Pierluigi San Pietro

  • Affiliations:
  • Politecnico di Milano, Milano, Italy;Politecnico di Milano, Milano, Italy and CNR IEIIT-MI, Milano, Italy;CNR IEIIT-MI, Milano, Italy;Politecnico di Milano, Milano, Italy

  • Venue:
  • Theoretical Computer Science - In honour of Professor Christian Choffrut on the occasion of his 60th birthday
  • Year:
  • 2006

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Abstract

Two formal models of pictures, i.e., two dimensional (2D) languages are compared: tiling systems and tile rewriting grammars, which resp. extend to 2D the regular and context-free languages. Two results extending classical language properties into 2D are proved. First, non-recursive tile writing grammars (TRG) coincide with tiling systems (TS). Second, non-self-embedding TRG are suitably defined as corner grammars, showing that they generate TS languages. The proofs exploit newly introduced language substitutions, also nested and iterated.