A note on unambiguity, finite ambiguity and complementation in recognizable two-dimensional languages

Abstract

The paper deals with some open questions related to unambiguity, finite ambiguity and complementation of two-dimensional recognizable languages. We give partial answers based on the introduction of special classes of languages of "high complexity", in a sense specified in the paper and motivated by some necessary conditions holding for recognizable and unambiguous languages. In the last part of the paper we also show a new necessary condition for recognizable two-dimensional languages on unary alphabet. © 2009 Springer.