A computational model for tiling recognizable two-dimensional languages

Tiling systems are a well accepted model to define recognizable two-dimensional languages but they are not an effective device for recognition unless a scanning strategy for the pictures is fixed. We define a tiling automaton as a tiling system equipped with a scanning strategy and a suitable data structure. The class of languages accepted by tiling automata coincides with the REC family. In this framework it is possible to define determinism, non-determinism and unambiguity. Then (deterministic) tiling automata are compared with the other known (deterministic) automata models for two-dimensional languages.