3 ms·

So, in the RSS spec, the <guid> tag is used to identify individual posts. Without some sort of identifier, it's hard to know if a user has e.g. already heard so

So, in the RSS spec, the <guid> tag is used to identify individual posts. Without some sort of identifier, it's hard to know if a user has e.g. already heard something in a feed (because new things can be added and old things can be removed). GUIDs, as defined in the RSS spec, are also not required to be globally unique - they're only supposed to be unique to the feed that includes them. This, combined with the fact that a feed that doesn't include them at all is still completely valid, is usually a pretty big stumbling block for developers looking to consume RSS. This is the biggest issue that got talked about during the Atom vs RSS discussion of a decade ago. And if you're referring to the UUID I'm automatically adding to every feed, it's so that there is an unchanging canonical way to refer to a feed that follows it across URL changes etc. The sibling comments get it perfectly.

PretzelFisch 10y ago
I see. I had to review the spec, I was under the impression that item's source element and URL required and used to locate the item. But I see that is not the case.
Animats 10y ago
My experience with processing RSS feeds is that none of the uniqueness indicators in feeds really work. The only thing that works is hashing the content and discarding duplicates. Etags are especially useless. There are sites with a load balancer in front of multiple servers, each with its own etag. As I've pointed out before, RSS feeds remain in widespread use for hard news. Almost all the hard news sites, including AP, NYT, Reuters, VOA, the BBC, etc. have useful RSS feeds. There are RSS feeds from NASA, feeds which tell you what Congress is doing right now, National Weather Service alerts, missing kid alerts, and California fire incidents. There's even a Donald Trump RSS feed. If it matters, it's on RSS. Social has gone in a different direction, but that's just the social media industry.

PretzelFisch 10y ago

I see. I had to review the spec, I was under the impression that item's source element and URL required and used to locate the item. But I see that is not the case.

Animats 10y ago

My experience with processing RSS feeds is that none of the uniqueness indicators in feeds really work. The only thing that works is hashing the content and discarding duplicates. Etags are especially useless. There are sites with a load balancer in front of multiple servers, each with its own etag. As I've pointed out before, RSS feeds remain in widespread use for hard news. Almost all the hard news sites, including AP, NYT, Reuters, VOA, the BBC, etc. have useful RSS feeds. There are RSS feeds from NASA, feeds which tell you what Congress is doing right now, National Weather Service alerts, missing kid alerts, and California fire incidents. There's even a Donald Trump RSS feed. If it matters, it's on RSS. Social has gone in a different direction, but that's just the social media industry.