[x2rj]

Atom is an order of magnitude more complex and strict standard by people who really love xml in contrast to the really simple and less strict rss 2.0. For example almost everything is optional in rss 2.0 so you can have a reasonable feed for stuff like tweets or linkblogs where there is no obvious title. In contrast atom enforces a title for every item which makes this a messy expirience.

I have implemented rss 2.0 parser faster then understanding the atom specification. Atom can do encode stuff like encode html inline the xml instead of as a CDATA string. In theory this sounds great, but is ends up in a big mess of complexity (e.g. a blogpost with handwritten invalid html).

These days there is also JSONFeed which is really easy to parse, simple and flexible, but it is not supported everywhere yet.

[simonw]

The RSS 2.0 spec has a horrible flaw:

https://www.rssboard.org/rss-2-0-1-rv-6#hrelementsOfLtitemgt

> An item may also be complete in itself, if so, the description contains the text (entity-encoded HTML is allowed; see examples)

Note "is allowed", not "is required". This caused SO MANY problems back in the day, because the spec didn't clarify if you should or should not include HTML in that element - and there was no way of telling, when parsing a feed, if the author was in the "entity-encoded HTML" or "YOLO and just stick plain text in there" camp.

IIRC, Atom came about precisely because the RSS specifications didn't provide the level of detail needed for a spec to be truly interoperable.

[eduction]

In practice, the description is universally considered to be html encoded. Everything is decoded. If you try to stick unencoded html in there it gets rendered as text. If you really don’t want to encode you can stick it in CDATA and it will just work per the xml spec. I’m trying to remember what the downside of this approach is - I think maybe it kept people from sticking unencoded ampersands in plain text or something.

But I think it’s worth noting that a cultural tradition emerged that papered over the flawed spec. I think that is actually pretty common with specs, even if the rss2 one is extra loose.

Maybe having a correct spec isn’t everything.

[ttepasse]

> But I think it’s worth noting that a cultural tradition emerged that papered over the flawed spec.

Back in 2013 a developer of a feed crawler wrote a selection of things people get wrong with their feeds.

https://inessential.com/2013/03/18/brians_stupid_feed_tricks

[eduction]

This is definitely a good example of "RSS culture."

(This particular one isn't papering over flaws in the spec, many of thse are advising against doing things that violate either RSS or XML spec, or are subjective opinions additive to the spec (e.g. always have a datetime). But ya this is basically what I mean.)

[talideon]

Atom is not a magnitude more complex or strict. It has _two_ places where it requires something even slightly onerous, and that's in the summary and content elements, where, shockingly, it allows you to specify if the content is XHTML, HTML, or text, and for HTML, it's just a matter of escaping the contents or putting it in CDATA. That's it.

I don't know what you're doing that RSS 2.0 is somehow faster to parse than Atom. I've written parsers for both over the past twenty years with a negligible difference between the two besides the fact that the RSS feeds often need hacks. I've also wrote a whole bunch of blog and linkblog backends that produce Atom feeds, and have never and issue with any. Let's look at the required elements of an entry: updated, title, id. Nothing remotely onerous there. In fact, it's purposely minimal, more minimal than RSS. And in RSS 2.0, title is a required element (because if something it's explicitly noted as optional in the RSS 2.0 spec, it's assumed to be optional).

In my personal linklog, I use the title of the target page of the link as the title, because it's the sensible option. With tweets, you have half a point. Only half a point, because title is required, but Twitter also post-dates the early 2000s considerably. But here's the thing: 'title' is required in RSS and Atom, but there's nothing saying it can't be empty. I know, I've blown your mind!

And then there's JSONFeed, which, of course, can somehow gracefully cope with people dropping '"' in random parts of the file because people generate JSON files like that by hand, right?

Right?

Just like they write RSS and Atom feeds, right?

Right?

[ttepasse]

> I have implemented rss 2.0 parser faster then understanding the atom specification. Atom can do encode stuff like encode html inline the xml instead of as a CDATA string. In theory this sounds great, but is ends up in a big mess of complexity (e.g. a blogpost with handwritten invalid html).

The same thing can also happen in RSS feeds (and JSON Feeds): Entity-encoded HTML strings or CDATA HTML strings do not have any guarantee of well-formed-ness. The direct embedding of XHTML into Atom as namespaced elements just surfaces potential invalid markup higher up.

[CharlesW]

> The same thing can also happen in RSS feeds […]: Entity-encoded HTML strings or CDATA HTML strings do not have any guarantee of well-formed-ness.

I wrote a podcast validator, and I don't think that's true — every RSS feed must be "well-formed" XML.

(Note that all "valid" XML documents are "well-formed", but "well-formed" XML documents are not necessarily "valid".)

[ttepasse]

I was talking about the (X)HTML in that RSS feed and its well-formed-ness.

In a perfect world people would construct their XML documents with an API which guarantees that the generated serialisation is a well-formed XML document. E.g. the API guarantees that the element tree is nested, that namespaces are declared and that the serialiser escapes any text nodes. Then people could add their well-formed XHTML fragments as a child to <atom:content type="xhtml"> and then serialise the whole document, guaranteeing well-formed-ness across namespaces.

In practice people have a tagsoup string from their data store which they concatenate inside their RSS template in <description>. If you’re lucky, they replace "<" and "&" beforehand or do the CDATA thing. But in XML terms that is just a string, not well-formed markup.

[CharlesW]

Interesting, thank you. Every podcast RSS feed (a tiny subset of RSS feeds) I've seen in the wild is well-formed in the strict XML sense, so the tagsoup problem must be more endemic on the text syndication side.

[ttepasse]

I can imagine that that is potentially a result of Apple’s dominant podcast directory. Podcasters submit their feeds to Apple’s Podcast Connect, which I think flags warnings and errors. Other forms of feed don’t have that big motivation to validate.