This post originated from an RSS feed registered with Java Buzz by Bill de hÓra. Original Post: It's just XML Feed Title: Bill de hÓra Feed URL: http://www.dehora.net/journal/atom.xml Feed Description: FD85 1117 1888 1681 7689 B5DF E696 885C 20D8 21F8 Latest Java Buzz Posts Latest Java Buzz Posts by Bill de hÓra Latest Posts From Bill de hÓra

James Holderness:"RSS 2.0 has a guid element that fits the bill perfectly, but it’s not a required element and many feeds don’t use it. As a result, aggregator authors are left guessing, and nearly every one of them guesses differently.

I can’t say for sure what algorithms applications are using, but after running 150 tests on more than 20 different aggregators, I think have a fair idea how many of them work.

As you would expect, for most the guid is considered the key element for determining duplicates. This is pretty straightforward. If two items have the same guid they are considered duplicates; if their guids differ then they are considered different.

If a feed doesn’t contain guids, though, aggregators will most likely resort to one of three general strategies – all of which involve the link element in some way."

And hence, Atom has an id element. File under Atom-is-a-cleaned-up-RSS2.0.