On Tue, 2012-09-25 at 18:22 -0400, Tom Lane wrote:
> Actually, after reading another message you sent, I thought you were
> going to respond that your proposed transforms feature would cover it.
I had thought about this some time ago, but it's clearer to think of
casts as associating two types, versus transforms associating a type and
a language. JSON and XML tend to be types.