Always New Mistakes

December 13, 2007

Idea: Embedding RSS comments in a content RSS feed

Filed under: Blogs — Tags: , , , , , , , — Alex Barrera @ 4:05 pm

Mark Evans had a nice question on his blog some time ago and while commenting it I got an idea. One of the biggest problems (among others) about blogs, comments and RSS is that you can’t have both at the same time. That is, you can’t download one RSS feed with the content and the comments (as far as I know, so if I’m wrong, please correct me). I am aware that some feed readers can display both, but it’s not mainstream yet. On of those systems is the one on which I had the luck to see at FOWA in London this year. They are doing an awesome job and their interface is very very cool. Anyhow, my idea is based on something I read on the latest OPML draft specification (2.0) by Dave Winer.

Most blogs and content platforms offer two RSS feeds. One for the actual content and another one for the comments. The problem with it is that you need to subscribe to both to get them AND most probably, your feed reader will display them as separate feeds. In my opinion this is a burden and it might be one of the reasons why we seeIdea lightbulb such low ratios of comments per subscriber. I always tell the same fact, but it’s astonishing, at least for me, that a blog like TechCrunch with 165k+ subscribers gets an average of 20-30 comments per post. So, looking at the RSS 2.0 specification I remembered that there is a <comments> tag for each RSS item where, in theory, you have a link to the comments. Now, getting back to the OPML draft, Dave added a new feature which I think could allow a better comment handling. The basic tag in OPML is the <outline>. This tag might have an attribute called type, which can take several values, among them the “link” value. Quoting the OPML specification: “An outline element whose type is link must have a url attribute whose value is an http address“. In the new specification, he added what he calls inclusion. That is, if the url of an outline with link type ends in .opml, the file will be downloaded and included when displayed. I think the idea is very cool, specially if we give it a little twist. I was thinking that if instead of doing the inclusion with .opml files, we do it with an RSS file and we add that capability to the <comments> tag in the RSS specification we could have a wonderful tool to include comments in a feed.

So, putting all this together we might end up with something like this:

An RSS file of a blog ( which has items like the following one:

<title>Twittories and the art of writing</title>
<pubDate>Thu, 13 Dec 2007 14:03:55 +0000</pubDate>

Now, if instead of having a comments tag like that, we mix it with the OPML notion of outline included link we could rewrite it as:

<comments number="2"></comments>

With that slight modification we can now have the number of comments we have and the xmlURL of the comment’s RSS feed for that post. What happens on the other side? Well, the feed reader must read that tag and include it as if it was part of the feed. Adding the number attribute allow us, on one side to show the readers how many comments the post has and on another hand lets the feed reader know if he needs to download the RSS feed of the comments again. Evidently, the number attribute will change with time if we have new comments and will be updated every time our feed reader requests the RSS feed.

So, what do you think of my idea? As with every thing I’m sure this issue has been discussed by someone before me and it might even have a different solution I’m unaware of. So please, if you know a cool way to handle comments drop me a comment and I’ll include it in the post.

UPDATE: This is what happens when you rush a post. You get it wrong. What I just described exists already and is known as wfw:commentRss. The only difference with what I was proposing is that the comment count is specified by a different tag (slash:comments), which by the way has nothing to do with the wfw namespace. Now, the commentRss tag was proposed in 2003. I’m quite fascinated as to why it hasn’t been adopted in feed readers yet. Some readers display the comments count, some others even parse the commentRss tag, but I don’t know yet of a reader that actually pulls that data based on the counter and collapse it with the content. Maybe you could even ask the user to activate that feature on a per post basis.



  1. looks interesting. I like the fact there are people looking to take a new tact on RSS readers. You should check out for another take on the RSS reader.

    Comment by buckpost — December 13, 2007 @ 7:57 pm

  2. The problem with any solution that just points at another feed url for comments is that any aggregator would have to poll every single feed supplied, so if you have 100 posts, does it then have to poll 100 different url’s? Of course that would never work, you could of course have something like inform you when next to check the feed, but the number of feeds would explode into figures that would be unmanageable.

    The only solution (and going back to your example of OPML) is to have a hierarchy so that comments are embedded in with the posts.

    We could also do with standardizing a RESTful interface to RSS/ATOM so that requests can be made to limit the amount of data to request.

    We have with spent a lot of effort overcoming these problems, and the only way to push forward these things is to gain mass adoption of any new standard by making it easy to adopt and there to be reason for it to be adopted. This will take time.

    Comment by Nick Halstead — December 14, 2007 @ 9:56 am

  3. Hello Nick,
    Glad to hear from you! First of all congrats on the Scoble review 😉 How was Leweb? I was going to go but dropped it at the last minute (for what I see, that was a bad idea TM).

    Well, I thought about the polling problem, that’s why using the number attribute (or the slash:comments tag) is of vital importance. If you combine both you don’t need to poll for both RSS. You poll for the content one as usual and keep track of the number of comments. When and only when the number of comments changes you poll for the comments RSS. So, even though you indeed make more connections, it’s still less than if you have two separate RSS, one for content and one for comments.

    Another way is to use something like Coment or the recent Adobe BlazeDS. But those solutions requite a very big architecture change for most blogs/platforms and will never happen.

    What do you think?

    Comment by alexbarrera — December 14, 2007 @ 10:14 am

  4. very interesting, but I don’t agree with you

    Comment by Idetrorce — December 16, 2007 @ 7:32 am

  5. Hi idetrorce, why is that? I would love to hear thesis against the idea because I’m sure that if it hasn’t been implemented mainstream it might be because of something. Please elaborate more 🙂

    Comment by alexbarrera — December 16, 2007 @ 12:12 pm

  6. Hi,
    Our RSS Server:

    Has commenting ability on the output direct in an RSS Reader, such as our Ticker.

    Please download the demo version and try it out if you dont believe me!

    Comment by Mike Jones — January 9, 2008 @ 4:05 pm

  7. Thank you for this interesting article. I have book marked this site because I hope you write more articles soon, I will definataly share this.

    Comment by Delaware — August 31, 2011 @ 3:26 am

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