> This problem doesn't exist for JSON, because pretty much every language directly supports arrays, objects/maps and primitives No, JSON will not map directly

> This problem doesn't exist for JSON, because pretty much every language directly supports arrays, objects/maps and primitives No, JSON will not map directly to a language with advanced type system (with tuples, variants, etc). Even in Elm it's recommended to write a decoder to convert incoming JSON into an internal structure. So in fact the mapping is very poor. And I see no difference in this regard: both XML and JSON is crap.