I'm old enough to remember when Google released AJAXSLT in 2005. It was a JS implementation of XSLT so that you could consistently use XSLT in the browser.

The funny thing is that the concept of AJAX was fairly new at the time, and so for them it made sense that the future of "fat" web pages (that's the term they use in their doc) was to use AJAX to download XML and transform it. But then people quickly learned that if you could just use JS to generate content, why bother with XML at all?

Back in 2005 I was evaluating some web framework concepts from R&D at the company I worked, and they were still very much in an XML mindset. I remember they created an HTML table widget that loaded XML documents and used XPATH to select content to render in the cells.