Compiling a Partition-Based Two-Level Formalism
  This paper describes an algorithm for the compilation of a two (or more) level orthographic or phonological rule notation into finite state transducers. The notation is an alternative to the standard one deriving from Koskenniemi's work: it is believed to have some practical descriptive advantages, and is quite widely used, but has a different interpretation. Efficient interpreters exist for the notation, but until now it has not been clear how to compile to equivalent automata in a transparent way. The present paper shows how to do this, using some of the conceptual tools provided by Kaplan and Kay's regular relations calculus. 
Edmund Grimley-Evans, George Anton Kiraz, and Stephen G. Pulman   (University of Cambridge)