Numerous models of probabilistic systems are studied in the literature.
Coalgebra has been used to classify them into system types and compare their
expressiveness. We formalize the resulting hierarchy of probabilistic system
types by modeling the semantics of the different systems as codatatypes.
This approach yields simple and concise proofs, as bisimilarity coincides
with equality for codatatypes.
This work is described in detail in the ITP 2015 publication by the authors.