Hello, I have been thinking about using Haskell for prototyping of business apps. I would rather use Haskell also for the persistency, global constraint maintanence, etc... rather than using an external database. The only thing I have found so far is HApps, but I haven't figure out how that works. Is there anything else? I guess I could just use lists for the relations, and the state monad. I would extend the record types witha deleted flag and a transaction number (i.e. simple multi version control). Then updates would just consist of pushing a new record onto the front of the list, and rollbacks and commits come for free. The only disadvantage I see that I always need to scan through the whole list all the time, which will get long, and might even be too slow for prototyping. The lists might also get too large memory wise. Any suggestions? Any libraries? Any experiences with HApps or prototyping business apps with haskell in general? Rene.