Autoprefixing (and other processing)

Where does autoprefixing fit into this? Should it be part of the library (like SC), or something that happens on this "standard" data format (i.e. directly before injection into the DOM). What about other processing things?

Potentially, if we went the latter, we could build a converter from this format (do we have a name!?) to PostCSS for people who really wanted it, it would be slow but maybe some people would want to make that tradeoff. For anything core (like prefixing, rtl) we could write optimised transforms, for anything else people could write their own.

Is that opening up a pandora's box of customisation/complexity?