Hi Anand MD5Digest is an abstract type (the constructor is not exported from its module) but it is an instance of Binary. ClockTime (from System.Time) is not an instance of Binary but it does export its constructor. Neither are instances of Data.Data. So I would hand-craft an instance of Binary for the Props datatype rather than try to first make them instances of Data. The code will be something like this, as I don't have MD5 installed it is unchecked: class Binary Props where put (Prop md5 tim name) = do { putWord8 0 -- number each constructor ; put md5 -- MD5Digest has a Binary instance ; putTOD tim ; put name } put Blank = do { putWord8 1 } -- number each constructor get = do { typ <- getWord8 -- get the constructor tag... ; case typ of 0 -> getProp 1 -> return Blank } getProp :: Get Props getProp = do { md5 <- get ; tim <- getTOD ; name <- get ; return (Prop md5 tim name) } -- ClockTime doesn't have a binary instance -- but a it has a single constructor -- -- > TOD Integer Integer - -- -- and Integer has a Binary instance, so I -- would make auxillaris for put and get: putTOD :: ClockTime -> Put () putTOD (TOD a b) = do { put a ; put b } getTOD :: Get ClockTime getTOD = do { a <- get; b <- get; return (TOD a b) }