Generalized Parenthesis Languages and Minimization of their Parenthesis Parts

Abstract A generalized parenthesis languages (gpl. for short) is a cfl which roughly speaking shows the nesting property explicitly by using some terminal symbols as parentheses. In other words, it abstracts the block structure prevalent in modern programming languages. In this paper we study properties of gpl's in relation to regular sets and cfl's, and solve some decision problems mostly affirmatively. For example, we prove that the regularity problem for gpl's is decidable, and more generally that one can find for a given gpl a minimal set of parentheses that can express the resting property of the language.