Once upon a time in old ASDF, there was an idea that one might put slots on operations. IIRC, this worked oddly, at best, because it wasn't clear how to propagate these slot values around in the plans that ASDF built.
OTOH, we could really use the ability to add information to some of the ASDF operations. For example, now that we have an IMAGE-OP, we really don't want the images hidden away in the .cache directory where they are hard to find.
Justification: it's fine to have fasl files hidden away there, because the fasls are loaded by ASDF:LOAD-OP based on computed fasl file locations. But if you want to load an image, you need to find that image *before* you have ASDF -- even before you have lisp -- so an invisible file, whose location is computed, is really inappropriate.
Note also that by Faré's design principle -- the one who knows should specify -- this information cannot be somehow programmed into the system -- it must be supplied by the user.
I'm inclined to think we could allow the user to set an output-file for some of the bundle operations with a keyword argument to OPERATE, and then jam the value of the keyword argument into the bundle-op for it to be written.
This works, I think, because it's a trivial case. If we try to put some properties on an operation and need them to be propagated around the plan, I think we just lose.
Comments?