[tannhaeuser]

Your points are appreciated. I think your graph-theoretical interpretation of the XML-vs-JSON debate, though, is missing the point that SGML/XML describes an information serialization using a grammar formalism (regular tree languages), as opposed to JSON which is essentially described by co-inductive type theorems. Though JSON is lacking because it can only represent trees rather than more general graphs, and because of JavaScript's very weak type system (eg. wrt. primitive types as well as it's lack of a natural type system for JSON compound types, hence requiring kludges such as JSON schema).