There is no answer in that space. What do I mean by a language.
Languages are to schema-defined graph types as object classes are to structured datatypes.
This is the stuff of the message, it is the territory, relative to namespaces, not the namespace-level map. We can define a set of progressively more detailed maps that tell more and more about the territory. And progressively higher levels of processing that respond to the distinctions in each incremental map refinement. Starting and ending with an Infoset, the pair of transformations is an identity, you get back the same InfoSet. After passing through InfoSet once, you thereafter get back a canonical string.