XML is not meant to be written primarily by hand (although I agree some XML languages could be more elegant). The markup part of XML is for the machine; if you

XML is not meant to be written primarily by hand (although I agree some XML languages could be more elegant). The markup part of XML is for the machine; if you remove it from your example, you'll get x=−b±b2−4ac2a, which is, basically, the text content that was meant for the humans. Now, as a machine language XML is much better than troff or TeX, because it's very easy to parse: it's basically a syntax tree, the result of parsing those other formats, you don't even really parse it, just deserialize. Naturally, it's a very good interchange format. Technically it would be a much better option than a full-fledged JavaScript parser and typesetter because it would've removed the parsing part. (And this is only one of the advantages.)