I would be nice if this was done in terms of MIME Types. Perhaps similar to the "Accept" header in HTTP (though in this case the invoker is telling the program

I would be nice if this was done in terms of MIME Types. Perhaps similar to the "Accept" header in HTTP (though in this case the invoker is telling the program (aka server) what types it would like). Of course this only solves the parsing problem, not the semantic one.