A user of RSS Bandit recently forwarded me a discussion on the atom-syntax mailing list which criticized some of our design decisions. In an email in the thread entitled Reader 'updated' semantics Tim Bray wrote

On Jan 10, 2006, at 9:07 AM, James M Snell wrote:

In RSS there is definite confusion on what constitutes an update. In
Atom it is very clear. If <updated> changes, the item has been updated.
No controversy at all.

Indeed. There's a word for behavior of RssBandit and Sage: WRONG. Atom provides a 100% unambiguous way to say "this is the same entry, but it's been changed and the publisher thinks the change is significant." Software that chooses to hide this fact from users is broken - arguably dangerous to those who depend on receiving timely and accurate information - and should not be used. -Tim

People who write technology specifications often have good intentions but unfortunately they often aren't implementers of the specs they are creating. This leads to disconnects between reality and what is actually in the spec.

The problems with updates to blog posts is straightforward. There are minor updates which don't warrant signalling to the user such as typos being fixed (e.g. 12 of 13 miner survive mine collapse changed to 12 of 13 miners survive mine collapse) and those which do because they add significant changes to the story (e.g. 12 of 13 miners survive mine collapse changed to 12 of 13 miners survive killed in mine collapse). 

James Snell is right that it is ambiguous how to detect this in RSS but not in Atom due to the existence of the atom:updated element. The Atom spec states

The "atom:updated" element is a Date construct indicating the most recent instant in time when an entry or feed was modified in a way the publisher considers significant. Therefore, not all modifications necessarily result in a changed atom:updated value.

On paper it sounds like this solves the problem. On paper, it does. However for this to work correctly, weblog software now need to include an option such as 'Indicate that this change is significant' when users edit posts. Without such an option, the software cannot correctly support the atom:updated element. Since I haven't found any mainstream tools that support this functionality, I haven't bothered to implement a feature which is likely to annoy users more often than be useful since many people edit their blog posts in ways that don't warrant alerting the user.

However I do plan to add features for indicating when posts have changed in unambiguous scenarios such as when new comments are added to a blog post of interest to the user. The question I have for our users is how would you like this indicated in the RSS Bandit user interface?