Geoffrey Sneddon wrote:
> To those on atom-syntax who've got this through being CC'd, 
> Habari currently uses one feed for both end users and the APP 
> collection, and is currently sorted by atom:updated (which is 
> currently any update, but seems to be little opposition to 
> fixing that) — the seeming issue is splitting the end user 
> feed and the APP collection up, as several are questioning 
> what the need to actually order by app:edited is. What really 
> is the need for it to be ordered by app:edited? I can see 
> nothing in the archives or on the wiki about the ordering 
> (apart from its introduction).

Usually a blogging server will implement app:draft in a way that the
collection feed will contain draft entries and the public feed won't.
So, you need (at least) two feeds anyway.

There have been many discussions on the atom-protocol list about how to
efficiently synchronize a client's copy of a collection with the
server's copy. Those synchronization mechanisms are based on the premise
that a client can page through the feed until it gets to an entry with
an app:edited timestamp that is earlier than the last time it synced,
and then stop. Unless you sort by app:edited, your server will not
interoperate with any client that works like this. 

When media resources (images, videos) are updated, the media link entry
in the collection feed for that media resource should have its
app:edited timestamp updated. If you insist on sorting by atom:updated
then make sure you update atom:updated in that case.

When I implemented an AtomPub server, I also found there to be some
performance reasons for implementing a separate collection feed. First,
you can combine all the media link entries with the regular entries in
the collection feed, but you would never want to do that for your public
feed. Also, there is really no reason for a collection feed for a blog
to contain anything close to the full content of the entry; if you cut
out all the optional bits of the entry (besides the summary, which is
sometimes useful for the blog editor), you can fit a lot more entries
per KB in the collection feed in your (usually full-content) public
feed, and/or you can make the collection feed pages much smaller. I am
usually able to fit about 4 blog entries per kilobyte (compressed) in my
collection feeds document, whereas the entries in the full-content
public feed are usually ten times that size.

- Brian


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