> We hear this too often: “XMPP uses XML. It should use JSON—it’s more modern.”

I can't take this write-up seriously if it starts like that. I still read the whole thing though and I couldn't find any solid argument as to why someone would prefer XML to JSON for XMPP.

> This is especially true in browser environments, where XMPP streams run over WebSockets, which naturally frames the XMPP protocol. That’s why you are never actually working with XML trees consuming large chunks of memory. Modern implementations like XMPP.js go further and use LTX—a lightweight parser built specifically for XMPP’s streaming model—rather than the browser’s DOM parser. The result: developers work with JSON-like objects anyway. The wire format becomes invisible to your application code.

That to me, is an argument for using JSON, not XML. XML is strong when you have elements referencing other elements in your document structure or DOCTYPE for grammar defs. I might be missing something but I don't get how streaming XML is to be preferred over JSON for XMPP.

If it was actually using XML as a markup language then that would be a reason to stick with it. But XML seems to be complicating things much more than it simplifies.

>> XML remains the best format for representing trees—deep hierarchies of nested data. JSON handles flatter structures well, but good messaging protocols are extensible: extensions can be embedded at different levels and composed together, like Lego bricks. That’s where XML shines.

Anything reasonable you'd be doing with messaging protocol is pretty flat.

It should be JSON with embedded XML for message text markup, playing to each ones strengths... not combining two sets of weaknesses by framing in XML and then using Markdown to format the messages.

Features complicate things, not markup. JSON protocols still do all the things xmpp does.

What part part, sorry?