Greetings, With acid-state-0.3, you can use regular Haskell data structures without worrying about data loss or durability. Your state will simply always be available to you even after software crashes or power outages. For examples of how to use the library, see: http://mirror.seize.it/acid-state/examples/ http://hackage.haskell.org/package/acid-state http://acid-state.seize.it/ -- Cheers,   Lemmih