[Haskell-cafe] singleton types

Hello, HaskellDB makes extensive use of Singleton Types, both in its original version and the more recent one where it's using HList instead of the legacy implementation. I wonder if it is possible, not considering feasibility for the moment, to implement HaskellDB *without* using Singleton Types. Luke Palmer demonstrates in one blog post replacing type classes with data structures, so I wonder if this could also be applied in this setting. Best regards Günther