Different types for different feeds

This is a rather strange and unlikely to be successful question, but I’ll ask anyway: do you, or anyone you know, have autodiscovery link elements for an equal number of different types of feeds, where the contents are actually different?

If you see

<link rel="alternate" type="application/rss+xml" href="/index.xml">
<link rel="alternate" type="application/rdf+xml" href="/index.rdf">
<link rel="alternate" type="application/rss+xml" href="/comments.xml">
<link rel="alternate" type="application/rdf+xml" href="/comments.rdf">

you might guess that an equal number of each type meant it was the same content in different formats, but is something like

<link rel="alternate" type="application/rss+xml" href="/index.xml">
<link rel="alternate" type="application/rdf+xml" href="http://del.icio.us/rss/user">
<link rel="alternate" type="application/atom+xml" href="http://user.blogspot.com/atom.xml">

too common to make that a safe guess? (And the bonus question, how many browsers failing to show more than the first feed would it take to make people change, by faking the type I guess?)

Extra credit for real-world example URLs, and for speed. Thanks.


Comment by Jacques Distler #
2005-08-08 22:47:43

You are proposing to hide some of the <link>ed-to feeds from the user, based on a heuristic that some of them might be duplicates?

Egads! What happens when the RSS feed(s) are excerpt-only, but the ATOM feed(s) are full-content ? (Or whatever.)

Comment by Phil Ringnalda #
2005-08-08 23:22:17

That rather depends: if it were code I was writing, for something that quacked like a normal feed reader, I would assume that Atom was most likely to please me (by having both a summary and full content, by giving me more things I could be sure of using, by telling me whether it was escaped HTML or escaped text), and if I thought that I was really seeing the same content in different formats I’d save the user the trouble of making a political decision since he probably doesn’t know the details of my relative abilities to parse and understand each format.

If it were someone else’s code, they might very well strongly (perhaps a bit too strongly) apply Mark’s decision that order is significant, and the first one rules, and thus if the first feed is application/atom+xml for a weblog entry feed, then only show the Atom feeds for that, the comments, the links, a photoblog, whatever. And if for some reason the first one is a less-happy format, they might choose that instead.

Of course if I was writing code for myself, I wouldn’t hide anything at all, because I know that for Live Bookmarks I want the RSS 0.92 feed from a WordPress weblog, because I’m only using the titles and links and it has the lightest description to ignore, and for my hacked up Feed on Feeds I want RSS rather than Atom for Textpattern weblogs because I don’t handle their escaping very well, and so on.

Apparently, knowing how to choose isn’t common knowledge among Real People, and since I don’t make the decisions for any (first feed: one click, others: PITA) browsers (um, sometimes our reach exceeds our grasp), about all I can do is ask if anyone knows of some good examples where a decision maker’s plan will fail miserably.

Comment by Adrian #
2005-08-09 00:01:00

From my quick test, Safari takes just the first feed when I click on the RSS button for my site (which now has 2 feeds but has had up to 5)

I had a problem with Kinja taking the second feed, and ignoring the first one. I just noticed this yesterday actually, and haven’t got around to mailing them on it. I thought it might have been because I had forgotten to take out some links to feeds I had removed, but the problem still seems to be there.

Comment by Aristotle Pagaltzis #
2005-08-10 20:52:12

Check my own blog, where there’s one Atom feed and one RSS one, which are completely different things. Their being on completely different hosts could be taken as an indication that they differ, but the reverse is not true, as I’ve seen plenty of people mirror their del.icio.us feed on their own site.

The only heuristic that sounds like it stands a chance to not be so horribly fragile as to be useless would be to look for identical non-empty titles.

At the very least, if you are going to formulate a heuristic, please go to the trouble of specifying a way for authors to bypass it by expressing precisely what they mean.

Comment by Phil Ringnalda #
2005-08-10 21:19:22

Ah, thanks mate! I thought I checked you when I was idly poking around for an example, but it might have been after I forgot what I was doing, and started just wandering aimlessly.

But what’s with all the second person singular pronouns in this thread? Just because bad ideas are usually mine, doesn’t mean they always are. All I’m doing is trolling for an example or twenty to stop Ben from making a bad decision for Firefox, based on something that’s good with the defaults for typical blogging software and horrible elsewhere.

Comment by Aristotle Pagaltzis #
2005-08-11 07:19:43

It was actually second person plural. :)

I do understand the desire for such a heuristic, I really do. I was just saying that if one’s put in place, I’d really like a way to override it, for use by people who (like me, I would like to think) know what they’re doing, or, at the very least, know what they want.

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