Hello to everyone :) My name is Enrico, 40, and I write software for the industry at Beta 80 Group. After this short introduction, here is the help request: I'm managing the rewrite of an application, to port it to the 'classic' Java three-tiers architecture. Before I begin to feed the team, I want to see a fully functional prototype of the problem. I mean the app's functions, not the graphic. What I imagine is a data base of types and groups of functions. The idea is to study the problem, inject new functions while checking their coerence with the existing type infrastructure, and so on. In plain Java, I'd have wrote the Business Idea in informal language, extracted the types from it, assigned methods to types and then glued things together in some way. In Haskell I (should) have the opportunity to stay on the problem, decomposing it into sub-problems until I come to the soil. What I ask to this list is if and where Haskell is different from the object oriented way to decompose the problem. I'm very fresh on Haskell. Exactly... chapter 13 of SOE :) Are type classes different from Java classes? I think so, but I guess this means that one should ask different things to type classes, respect to what is being asked to Java classes. It is this difference that's unclear to me. Any help would be very appreciated Enrico