SCHMID, M.L., 2012. Inside the class of REGEX Languages. IN: Yen, H.-C. and Ibarra, O.H. (eds.) Developments in Language Theory. Lecture Notes in Computer Science, 7410, pp. 73 - 84.
Lecture Notes in Computer Science;7410
We study different possibilities of combining the concept of homomorphic replacement with regular expressions in order to investigate the class of languages given by extended regular expressions with backreferences (REGEX). It is shown in which regard existing and natural ways to do this fail to reach the expressive power of REGEX. Furthermore, the complexity of the membership problem for REGEX with a bounded number of backreferences is considered.