This argument has a got a bit sidetracked. My position is:
a) I think title-only feeds should be allowed where there's nothing sensible to put in the summary or content elements.
b) Under all other circumstances, a summary of some kind should be required when atom-based textual content is absent.
The pace as written newly allows the omission of a summary and content on the whim of the publisher. It also allows its omission when the content of the entry has been placed in a non-atom container. My first problem is that neither of these consequences seem intended. My second is that it is the interopability issue. I'm within my rights as a consumer to reject title-only feeds as not worth bothering with (before you condemn this as an arbitrary decision, bear in mind the current Atom spec makes the same judgement). The atom spec would not give publishers fair warning of this. This is why I think it makes more sense as a "SHOULD" requirement.
(btw The list of scenarios reprinted in the Pace doesn't mention whether you MAY include atom:summary outside the MUST cases)
Graham
