Tiling recognizable two-dimensional languages

  • Authors:
  • Dora Giammarresi

  • Affiliations:
  • Dipartimento di Matematica, Università di Roma "Tor Vergata", Roma, Italy

  • Venue:
  • CAI'07 Proceedings of the 2nd international conference on Algebraic informatics
  • Year:
  • 2007

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Abstract

Tiling recognizable two-dimensional languages generalizes recognizable string languages to two dimensions and share with them several properties. Nevertheless two-dimensional recognizable languages are not closed under complement and this implies that are intrinsically non-deterministic. We introduce the notion of deterministic and unambiguous tiling system that generalizes deterministic and unambiguous automata for strings and show that, differently from the one-dimensional case, there exist other distinct classes besides deterministic, unambiguous and non-deterministic families that can be separated by means of examples and decidability properties. Finally we introduce a model of automaton, referred to as tiling automaton, defined as a scanning strategy plus a transition function given by a tiling system. Languages recognized by tiling automata are compared with ones recognized by on-line tesselation automata and four-way automata.