You mean, like they did with DTDs, RelaxNG, and XSD (and probably half a dozen ill-conceived solution that died a well-deserved death)? Different XSD implement

You mean, like they did with DTDs, RelaxNG, and XSD (and probably half a dozen ill-conceived solution that died a well-deserved death)? Different XSD implementations do have slightly different ideas on interpreting the schema. (e.g., if your data has a bunch of A tags, then a B tag, then another bunch of A tags, do you include two occurs:unlimited statements for the A's or just one?) By the way, Javascript works just fine as a "query" language for JSON. Not as good as XPath or XQuery work for XML, but definitely better than any XML DOM manipulation in Java or another language would.