Hi, I refer to Section 5.3 (title see subject line) in Type classes: exploring the design space by Simon Peyton Jones, Mark P. Jones and Erik Meijer HW 1997. There it is argued very briefly that a type system with controlled scope of instances risks coherence. Likewise, in Wadler's and Blotts original paper on ad-hoc polymorphism, Appendix A.7 sheds light on the related problem of principal typings. Global scope is suggested while wondering about less restrictive conditions that retain principal typing. The interaction with the module system is not really considered. I also know of /Functional Pearl: Implicit Configuration -- or, Type Classes Reflect the Value of Types/ Oleg Kiselyov, Chung-chieh Shan, Haskell Workshop 2004, which sheds some fancy light on the subject. The paper deals with local instances, but not so much with scoping via the module system. Does anyone know of a published, somewhat deeper analysis regarding the possibility to scope instances via the normal module system? For instance, why can't we have as many distinguished "incarnations" of a class in the type system as there are different sets of instances created in various scopes. That is, references to methods are to be *implicitly qualified* by the corresponding class incarnation (i.e., sets of instances). Methods of different incarnations are not to be confused by the type system. This would solve all coherence issues that I can think of. Or is this just getting too complicated? Any pointers greatly appreciated. Regards, Ralf **