... that’s a laugh of bitter jealousy. I’ve dealt with XML, but I’ve never with XML that came with a schema, or which would have reliably followed one. Not saying schema-less formats are great, but at least I can eyeball them to see what is going on.
If I saw a schema, which I often didn’t, it usually didn’t say what the author thought it said. To a first order approximation, all the good ones I saw came from one tool (XMLSpy possibly?)
Namespaces ended up in a sort of uncanny valley that I can’t quite do justice to.
how about docbook? It's been a while, but I think even eclipse's project.xml used to have a schema, and would validate it if you tried modifying it yourself.