NetNewsWire and Update Checking
He hits the nail on the head: a headline has three, not two, states: unread, read, and updated.
NetNewsWire isn’t that smart about this. When comparing an incoming headline to an existing headline, if they’re the same but for a word here or there, NetNewsWire will mark it as a new headline. Which is annoying.
Luckily, there’s at least a partial solution. Later versions of RSS include a guid element which identifies a headline. This way you can tell that an incoming headline is the same as a previously-read headline, even if they’re different, because the guid is the same.
NetNewsWire already reads and stores guids, but it doesn’t do anything with them yet. In an upcoming release it will look at guids in deciding if an item is new or just updated.
Unfortunately, not all RSS feeds contain guids. My hope is that more and more they will since they’re so useful, since they make reading news so much better.