Parallel Replacement in Finite State Calculus
  This paper extends the calculus of regular expressions with new types of replacement expressions that enhance the expressiveness of the simple replace operator defined in Karttunen (1995). Parallel replacement allows multiple replacements to apply simultaneously to the same input without interfering with each other. We also allow a replacement to be constrained by any number of alternative contexts. With these enhancements, the general replacement expressions are more versatile than two-level rules for the description of complex morphological alternations. 
Andre Kempe and Lauri Karttunen (Rank Xerox Research Centre, Grenoble   Laboratory, France)