feed-level atom:modified

["Roger B." <roger@xxxxxxxxxxxxxxxxxx>]

On a lark, I was fiddling with translating Mark's MT Atom template into
something JournURL can use, and I ran into a wall... the mandatory,
feed-level modified element.

Consider these items:

<entry>
 <modified>2003-12-01T01:00:00Z</modified>
 <issued>2003-12-13T01:00:00Z</issued>
</entry>
<entry>
 <modified>2003-12-02T01:00:00Z</modified>
 <issued>2003-12-02T01:00:00Z</issued>
</entry>

What's the modified date for the feed? The items were last updated by the
user on December 2nd, when the second entry was added. However, the first
entry was published into the future, and is showing up in the feed for the
first time today. So in this case, it would seem the feed-level modified
date should be derived from the most recent issued date.

But bearing that in mind, what if I update the second entry today?

<entry>
 <modified>2003-12-01T01:00:00Z</modified>
 <issued>2003-12-13T01:00:00Z</issued>
</entry>
<entry>
 <modified>2003-12-13T06:00:00Z</modified>
 <issued>2003-12-02T01:00:00Z</issued>
</entry>

The feed is now different, with an updated modified date and (presumably)
updated content. So suddenly it would be more accurate for the feed-level
mod date to be derived from the most recent modified date.

Then I run into problems with search-derived feeds. A set of entries can be
the result of a search, with the items ordered according to their rankings
within the index. For example, a search feed for "foo" might return the top
two hits like so:

<entry>
 <issued>2003-12-13T01:00:00Z</issued>
</entry>
<entry>
 <issued>2001-10-02T01:00:00Z</issued>
</entry>

But as the index is updated, those entries may drop out of the top two and
thus out of the feed, to be replaced by items published (or updated, for
that matter) at earlier dates:

<entry>
 <issued>2003-10-21T01:00:00Z</issued>
</entry>
<entry>
 <issued>2002-12-16T01:00:00Z</issued>
</entry>

If an aggregator simply treats the feed-level modified element as an Etag of
sorts, noting any change and taking action, then things will be fine. But if
the aggregator treats it as an actual date, the feed will look older than it
did before the index updated, even though the content has changed
completely. In either case, I don't see how that pesky modified element is
actually *helping* anything.

So is there something I'm missing? Is there a specific reason why modified
is required at the feed level? I tried to dig through the wiki, but didn't
have the stamina required to mine anything useful.

--
Roger Benningfield
JournURL: http://journurl.com/
blog: http://admin.support.journurl.com/