Wednesday, May 23, 2007, 9:11:09 PM, A. Pagaltzis wrote:
>> For performance reasons a client paging through a feed may wish >> for the feed entries to be ordered in a particular way. > … these clients are broken if they can’t handle arbitrary > ordering. > If you want to do such a thing, then you would have to define an > extension element (placed at the feed level, at the top of the > feed, along with the other feed metadata) that describes the > order. > A client could then use this optional information, where it is > present, in order to optimise its processing. > RFC 4287 itself makes no such provision, though. ... and there is no guarantee that such an extension would work, because by overriding RFC4287s assertion that a feed is unordered, the extension would effectively have mustUnderstand semantics, which Atom doesn't support. Just because the publisher has added an <ex:ordered /> element, doesn't mean that services like FeedBurner, Yahoo Pipes, and whatever else haven't changed the order and passed the <ex:ordered /> element through. If these services knew of the <ex:ordered /> element, then they would know to strip it if they change the order, but you can't expect those services to know anything more than RFC 4287. ... Having said that, Microsoft's Simple List Extensions for RSS [1] might be useful. They allow you to specify a sort order for display of a feed, and the default sort order additionally acts as an assertion that the feed is physically sorted in that order. The caveats above still apply though. [1] http://msdn2.microsoft.com/en-gb/xml/bb190612.aspx -- Dave
