You really want me to say more? You seem to have missed the point of my reply. You said "all modern publishing uses XML", and in doing so, you were overlooking

You really want me to say more? You seem to have missed the point of my reply. You said "all modern publishing uses XML", and in doing so, you were overlooking the biggest counterexample to XML, and the biggest thing in modern publishing, which is HTML 5. HTML is a huge, huge example of modern publishing. It tried XML, when HTML 4 came along with XHTML. XML was basically designed around making XHTML work. And then HTML stopped using XML in HTML5. It took a revolt of all the implementers of HTML, but people got behind it because everyone could tell that XML wasn't helping. So now you've got a syntax that was designed for marked-up documents, that people don't really want to use for marking up documents, and it's also trying to convey data structures despite that this involves horrible patches like "xml:space" that no other format needs. You were also hinting at APIs for communicating things like time zones and chess moves. Real APIs don't use marked-up natural language. I work in natural language processing, and to a first approximation, computers don't understand shit about natural language. When you need to communicate data, you use data structures. If you want to communicate extensible data structures with hints about their semantics, you've got some choices, like protobufs and JSON-LD. Or you can keep patching XML and trying to make it convey data structures despite that data structures aren't made of marked-up strings, but then people won't use your API. XML is also an unwieldy format for parse results. It's not a frozen syntax tree, it's a tree with tons of stuff bolted on to the side. The format that represents a syntax tree is S-expressions.