Is the set of languages expressible using XML a superset of the set of languages expressible using JSON?

Hi Folks,

An XML language can be created to express Bookstores. Another to express network router data. Another for census data. And so forth.

The set of XML languages that has already been created is vast and diverse.

How big is the set of possible XML languages?

How big is the set of possible JSON languages?

Is the set of possible XML languages a superset of the set of possible JSON languages? If yes, would you give an example of an XML language for which there is no possible JSON language?

/Roger