Related Paper
"Type-Safe Observable Sharing in Haskell",
Proceedings of the 2009 ACM SIGPLAN Haskell Symposium, 09/2009.
Abstract
IO Reification
data-reify provided the ability to turn recursive structures into explicit graphs. Many (implicitly or explicitly) recursive data structure can be given this ability, via a type class instance.
See the Haskell Symposium paper (below) for more details.