I said, accidentally:

IMO, given the current design of Haskell 98, instances should be considered to be global. There is only room for one instance for each type/class pair in any program (including the libraries). Otherwise the library documentation has to publish for each module, a list of all the instances defined by it and all modules below it in the dependency tree. I think this is just silly.

Of course, the library documentation still has to publish the list of modules from which an instance can be imported. I meant to delete the above paragraph before sending the msg. Please disregard. Cheers, Simon