Picture iteration and picture ambiguity

摘要

Picture iteration theorems for regular, linear, and context-free languages are presented. These theorems serve as picture-counterparts of the well-known string iteration theorems and suggest that regular, linear, and context-free languages describe large pictures by iterating small picture primitives. It is also shown that the picture ambiguity problem is undecidable for regular languages and for linear languages which describe three-way stripe picture languages.