Technical Blog

Comment Aggregation

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There has been much discussion recently about comment syndication. I have made some of my own contributions to this, including Commentosphere and Blogger Recent Comments. While all of this is good and useful in its own way, syndication is useless without aggregation.

Currently, to track comments for interesting discussion / replies to your own you must subscribe to many comments feeds from different blogs and posts. This will quickly clutter your feedreader even if you only subscribe to the ones that are most important. Something that can help this, at least a little, is combining the feeds together into one megafeed, using something like feedshake or the Commentosphere Aggregator (see my aggregator for an example). While this works to some degree, it is ultimately unsatisfactory.

So here’s the idea — have feed readers aggregate comments alongside the post. A post then appears unread if it has unread comments as well as if it is itself unread. The new comments are highlighted on viewing the feed and marked unread. Another possibility would be to have a little ‘comments’ icon next to the post title that shows if there are no comments, new comments, or all read comments on a post. Clicking the icon would bring up the comments for that post (likely within the aggragator, not just a link to the # or anything like that).

This whole idea does, of course, assume that the aggregator can get to the comments somehow. There needs to be some way to take the link URL (usually to the post page) and get the comments feed URL for that post. (Assuming there is one. If there isn’t, that’s in the realm of syndication, not aggregation.) To facilitate this, I am proposing a simple piece of standard markup. Most blogs that have comments feeds for every post have a link to that feed somewhere on the post page. If we made it standard protocol to set rel=”alternate comments” (obviously, just like with relTag, you can have other things in the rel-list as well, but require both of these) for these links, the aggregators could pull them out of the page and get the appropriate URL. The aggregator could then get the comments feeds and use them to produce the features outlined above.

5 Responses

Johan Sundström

The comment feed URL needs to get embedded into the main page feed itself too, to get accessable to feed readers. This is good for many other reasons, including autodiscovery of comment feeds tied to specific posts and tied to the blog in general.

For a decent kludge until that has been standardized (unless it has already happened in RSS and/or ATOM — I have not confirmed whether that might be the case already), I think your extension to the link attribute is a decent start.


I’ve thought about embedding the comment feed URL in the feed itself, since that would certainly be easier to use in the feedreader. RSS2.0 has a ‘comments’ tag for items, but it is meant for the URL to comments in HTML (ie #comments) and not a feed URL.

While the feed formats could easily be extended (it’s been done before, and most popular feedreading APIs that I’ve seen support ‘non-standard’ fields), I felt that such a move might be a tad out of place. Using this (or perhaps, alternately, a <link> tag with the same rel attributes) the feedreader can still get the URL, without having to change the feed format (since we can’t do that in Blogger or many other services anyway).

Johan Sundström

Well, “can’t” is a strong word (or two); I wouldn’t be so sure about that — we can’t do it on and of our own accord, but Blogger, like any party that wants to stay in the loop, will probably eventually join up with the crowd, as we (or others) move the frontiers forward.

Besides, we actually can; neither you nor I promote the Blogger feed URL in our page auto detect settings; we both use a Feedburner improved version (and format changing) feed derived from the original, which has already underwent substantial modifications from the markup of the source content.

Nothing stops us from adding another layer of comment linkfeed markers atop that, either with help from the busily growing and self-improving Feedburner service’s crew, or by ourselves, perhaps by making another Ning application that takes a post URL and creates a comment feed channel for it, while also piping a Feedburner feed through itself, layering said comment feed’s URL atop appropriate link elements within the feed.

It’s just technology; anybody that proclaims themselves king over the territory may rule as they see fit. Standardizing things as we go along makes it more useful and increases chances of landslide popularization, but if it’s good technology and easy to use, adoption will pretty much grow by its own accord.


You’re right — I certainly hadn’t thought that far. In doing a bit more research I found, not surprisingly, that someone has already done this. The wfw:commentRss is, I believe, an extension to RSS1.0 that does exactly this. While I think it’s meant for RSS1.0, including in RSS2.0 would probably work as well.

As another interesting thing — there is also some work going on to post comments from the reader as well.


Ok, I’m just posting a comment to test out my new Commentosphere account 😛

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