Regular language matching and other decidable cases of the satisfiability problem for constraints between regular open terms

Abstract

In this work, we investigate computational complexity of the solution existence problem for language equations and language constraints. More accurately, we study constraints between regular terms over alphabet consisting of constants and variables and based on regular operators such as concatenation (̇), sum (+), Kleene-star (*). We obtain complexity results concerning three restricted cases of the constraints: for system of language equations in which one side does not contain any occurrences of variables in case arbitrary solutions and with restriction to finite languages; for constraint in form L R, where R has no occurrences of variables. © Springer-Verlag 2004.