True but earlier: it was the HTML replacement that was also a data, description language. It's how I was introduced to it. I remember the tools were ridiculously overpriced: $100-200 for XML editor. Sold as better than SGML, which nobody wanted to even look at. Yet, any use of it for years required expensive 3rd party libs or my own custom PERL scripts. I said "I'll pass..." ;)

> XML was pushed by SOAP and Java frameworks, while S-expressions were only used by simple software that solved small problems.

I'd argue that S-expressions are used by simple software that solves complex problems, but I'm a bit biased