For folks that aren't aware, Michael and I have been discussing the AIX package tagging problem via email since his initial distutils-sig posts about it.

It's genuinely murky as fixing the AIX problem doesn't *technically* require any PEP 425 changes, as the main problem with the status quo is in the way the platform string is calculated, rather than in the way that then gets incorporated into a PEP 425 compatibility tag.

I think the subtlety I may not have cconveyed clearly though is that installers only do exact string matches on platform tags, working through a set of increasingly less specific candidates.

So if the goal is the same model that we use for Windows and Mac OS X, where the Python interpreter build defines the exact platform string that packages need to use, then all that's needed is the new platform string logic. That then places constraints on how AIX extension modules are built, but doesn't require a new PEP for installer logic changes. I think this is a good level of support to target.

There's then a further option that *would* require a new PEP: teaching installers to be more permissive in the compatibility tags they accept for AIX, based on the AIX ABI compatibility guidelines. I *don't* think that's a good idea - better to deal with that on the publication side, the way it is done for Windows and Mac OS X extensions.