d.hs

data Scalar
     = SInt Int32
     | SFloat Float
     | SBoolean Bool
     | SString Text
     | SEnum Text -- unquoted on parse

data InputValue
     = IVar Text
     | IScalar Scalar
     | IList [InputValue]
     | IObject (HashMap Text InputValue)

data ResponseValue
     = RNull 
     | RScalar Scalar
     | RList [ResponseValue]
     | RObject NodeHandler
       
data KeyHandler = KeyHandler (HashMap Text Main.Value -> IO ResponseValue)
data NodeHandler = NodeHandler (HashMap Text KeyHandler)

data Server = Server
              { rootQuery :: NodeHandler
              }