>XML is a great language since it has the power of schemas and DTDs. It makes it easy to validate the data you expect in each of the fields.
Quite the opposite. XML Schema is an awful mess - it's not even representable in XML; it's not a good language for expressing validation constraints, it's neither simple enough to be easy, nor powerful enough to express all your requirements. And the need to support schema leads to DTDs and namespaces, which are responsible for most of the screwups of using XML in the real world.
If XML were just tags, parsers didn't try to connect to the internet to validate everything, and tools didn't bother with namespaces, it would be usable enough that we probably wouldn't have needed to invent JSON.
