The following lists which elements can appear in atom:head and atom:entry according to the current draft. I think any proposal to unify head and entry needs to explicitly address each of the differences and explain a) why there's no reason for both head and entry not to contain each or them, or b) why each should disappear or be moved elsewhere in the format, or c) why it's okay to say "head and entry are the same except for these differences".
Element Name Head Entry ============ ==== ===== title Required Required link Required Required introspection Yes No post Yes No[1] edit No[2] Yes author Required Required (required in head or in every entry) contributor Yes Yes tagline Yes[3] No id Yes Required generator Yes No copyright Yes Yes info Yes[4] No updated Required Required published No[5] Yes summary No[3] Sometimes Required content No Yes origin No Yes
[1] atom:post in atom:entry as a pointer to a comment feed don't seem unreasonable to me.
[2] atom:edit for atom:head makes sense to me.
[3] replacing atom:tagline with atom:summary sounds reasonable if not exactly precise in meaning.
[4] I'd say atom:info should be removed from atom:head except that part of the purpose of atom:head is to make the ordering rules for children of atom:feed simple, and perhaps even so. I don't think I'd be too disappointed if atom:info just disappeared. We could (dons asbestos suit) use <link rel="format-explanation" ... /> to point to an explanation of the feed format if we feel the need to reserve a method of educating view-sourcers.
[5] I guess you could conceivably have atom:published in atom:feed--sort of a "serving your information needs since 1894" sort of thing.
Other differences:
* introspection - I'm not up on what the introspection file is all about enough to comment on this one
* generator - I don't see this making sense in entry
* content - I don't see this making sense in head
* origin - I don't see this making sense in head
* id: required in entry, not in head - as it should be
* if tagline becomes summary, the fact that it's sometimes required in entry, but never in head - as it should be
