[Standards] Re: Reinstating XHTML-IM (XEP-0071)

I think we are saying the same: 1. Self-closing tags work for foreign elements 2. Self-closing tags work for valid XHTML tags if they are void tags in HTML, because the self-closing '/' mark is not necessary and effectively ignored when parsing. 3. However, self-closing tags for valid XHTML tags that are raw text or normal element in HTML (e.g. <span />, <script />, <div />) do not work when parsed as HTML, because, again, the self-closing '/' mark is ignored, but that means that the HTML parser considers the tag not closed, meaning it remains opened and thus turns the valid XHTML into invalid HTML. The last is not some weird XHTML mime type extra, it's just that changing the MIME type can trigger supporting browsers to use the XML rather than the HTML encoding of HTML. And in the XML encoding it's perfectly valid, because the self-closing tag is actually treated as one. That's by the way not an obscure example. This happens in the wild a lot, the most common case is <script src="[..]"></script> which is the only valid way to embed a javascript from a remote source in HTML encoding. Notably the short <script src="[..]" /> is not valid in HTML, but in XML encoding it's even the canonical form. Which means that for many HTML web pages, if you turn them in canonical XHTML form, they will actually be invalid in HTML encoding. And just to remind why that's relevant: It means that a HTML parser that only supports the HTML encoding and not the discouraged XML encoding will not be able to (correctly) parse valid XHTML as is. Also a relevant note is that XHTML(-IM) allows for mixed content. Mixed content is not used elsewhere in XMPP and some XML parsers used in XMPP don't fully support it. XHTML-IM also uses CSS, which is another language that's actually not XML, so even if one resided to not pass the XHTML to a HTML parsing library but directly implement the parsing/processing based on the XML parser already present for the XMPP document, one would still need a CSS parser. And again, XEP-0394 is not an attempt to re-invent HTML. (X)HTML is invented for documents, it's simply not a good fit for markup of non- documents like IM, mostly because messages are usually not displayed as a document within a frame or similar, but rather in various ways, depending on the client and platform. XEP-0394 is a markup specifically targeted towards the messaging usecase and built such that the main body is not duplicated to achieve backwards-compatibility. Anyway, I don't think this discussion is going to lead anywhere. I do wonder though if there are any actual implementations of XHTML-IM as described in XEP-0071 are out there. If not, that IMO confirms it really is not needed. Marvin On Sun, 2026-03-15 at 15:22 -0500, Stephen Paul Weber wrote: