How digg reader finds the feed url[s] for a given site?

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It is that we can add a url to digg.com reader to add them to one's reading list. Once we submit the link they(digg) find several links which points to the feed map(.xml or from feedburner etc). How do they do this ?

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Julien Genestoux On

Feed discovery is step 1.

Step 2 is probably to have a "reverse" discovery mechanism. Each feed (RSS or Atom) as a link to an HTML representation. So, even if the other discovery part is missing you can still find a feed URL from a site if you have that 2nd relation... Combine that with user data (number of subscribers... etc) and you get a pretty good solution!

Step 3 is "dumb" search: each story in a feed has a link to domain. The feed itself has a domain. If they both match, you likely have found the feed you're looking for!

There are probably other techniques too :)