| I am trying to get a deeper understanding of core's role in GHC and | the compilation of functional languages in general. So far I have You can find lots of stuff here http://hackage.haskell.org/trac/ghc/wiki/Commentary. At the bottom is a link to a lot of GHC-related papers. | - Exactly what are the operational and denotational semantics of core? It'd be good to have a canonical place where this was written down, I agree; but it's totally straightforward. (The operational semantics, at least.) As Kirsten says, the FC paper is the most up to date presentation. | - The headline reasons (and any other arguments that emerge) for | having core *and* stg as separate definitions. You can find a description of STG, which describes the differences from Core, in the Commentary http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/StgSynType There is a lot of stuff in the Commentary! Simon