If you take anything away from that: brackets are the most compact way to serialize a tree, for some reason they are called s-expressions. The parse tree for lisp is the syntax tree, you just rename each bracket node to whatever the first atom in the bracket happens to be.

One thing that XML could have done that s-expressions can't is a way to serialize a dag if proper nesting of tags wasn't required. I'm playing around with a language based on that, the mental load of having no clear way to delineate blocks visually makes it hard to reason about, unfortunately.