Finite-State Non-Concatenative Morphotactics
  Finite-state morphology in the general tradition of the Two-Level and Xerox implementations has proved very successful in the production of robust morphological analyzer-generators, including many large-scale commercial systems. However, it has long been recognized that these implementations have serious limitations in handling non-concatenative phenomena. We describe a new technique for constructing finite-state transducers that involves reapplying the regular-expression compiler to its own output. Implemented in an algorithm called compile-replace, this technique has proved useful for handling non-concatenative phenomena; and we demonstrate it on Malay full-stem reduplication and Arabic stem interdigitation. 
Kenneth R. Beesley and Lauri Karttunen