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May 02, 2005


Eric Lunt

I totally agree with you, Bob, and I just wanted to assure you that FeedBurner is *not* adding that bit of HTML to the posts. Those links are in the source feed and we're just passing them through.

Eric Lunt


The problem goes away if advertisers and the reader software use the GUID to determine new items.

Nico Lumma

the ord-part has been around for a few years, it's doubleclick's implementation of a random number that is necessary to track unique page impressions.

Randy Charles Morin

I'm gonna disagree here. The RSS client shouldn't be using a hash of the to determine if the entry is new. It should be using the . That's what the is for.

[Bob Wyman Responds:
Randy, Unlike the atom:id, which is a required element in Atom entries, the RSS GUID is an *optional* element. Thus, it cannot be relied upon for duplicate detection. As an optional element, GUID is often not present. Additionally, we find that the GUID is often not a unique identifier even when present. In the future, we'll be able to use atom:id when detecting duplicates in Atom entries, but we can't consistently use the GUID when detecting duplicates in RSS. This distinction is one of the reasons that I hope that the community will be moving to Atom files as soon as the IETF approves Atom V1.0. With Atom files, we'll be able to detect duplicates much more effectively then with the old-style RSS feeds.

Randy Charles Morin

Bob, that GUID is often not unique has nothing to do with RSS. This non uniqueness will translate just as well to Atom.

Andy Henderson

The guid should be used to determine uniqueness if available IMO. However, that's not going to completely solve the problem. If someone has expressed an interest in monitoring an item, the changed advert text will still appear to the Aggregator as a change in the item itself which will be - incorrectly - highlighted to the user. Unless, of course, the advert is stripped before the comparison.


Roger Benningfield

Bob: I've run that feed through the two aggregators I use every day, and I'm not seeing any duplication. So either DC heard you and made a change, or this is a PubSub-specific problem that needs to be addressed on your end.

Bill Flitter

Good observation Bob. Pheedo is working with a group of industry leaders to present best practices on ads in feeds. We will be posting more information on our blog in the coming months. We will be asking for input from the community.

Jonathan Aquino

Rather than check the description for changes, why not just check if the link has changed? That would probably be a lot more robust (and simpler).

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