For those that are having trouble with arrows formalisms http://www.haskell.org/arrows/ http://www.haskell.org/arrows/biblio.html#Hug00 Additionally if you follow the links off this you should find a GUI toolkit based on arrows. For those who'd like to learn Maude http://www.ifi.uio.no/inf220/KompendiumPartI/komp/node1.html This seems a better tutorial than the set presented on the Maude site. Alexis