Unplug your machine and restart and have your app recover to exactly
where it left off. Happstack-State spares you the need to deal with all
the marshalling, consistency, and configuration headache that you would
have if you used an external DBMS for this purpose. Its component model
makes it easy to compose big applications from smaller reliable parts.
Use event subscription to trigger IO actions and support comet-style or
Obtained from: FreeBSD Haskell