httpwebwitch - 12:07 pm on May 16, 2011 (gmt 0)
You can create any "language" you want by extending XML; For instance a Schema that's all <car> with <part> and <gas> and <exhaust>; that's not HTML, it's markup for something else. I wouldn't call it a new language (it's XML) but it's not HTML, so there it is.
You can argue that every XML Schema is its own "language".
You can in fact, use XSL to transform XML into anything you want like JSON or CSV or just a paragraph of madlibs text, or anything you care to invent