[Haskell-cafe] What's this pattern called?

Bonjour café,

data ExprF r = Add r r | Sub r r | Mul r r | Div r r | Num Int

This is a well-known pattern that for example allows nice notation of morphisms. But what is it called? I've heard fixed-point view, open datatypes and some others, but I'm curious where this pattern comes up in literature and what it is called there. Thanks, Martijn.