I have used both XML and JSON over the years. XML has full and proper support for XSD and great XSL. It also allows really tight security for messaging. Not had the same tightly secure messaging experience with JSON can not completely judge this! Is the a standard for doing it - I don't know. XML appears to me to be much better able to be validated. JSON is very quick JSON Schema seem to be quite good but not as tight as XML. In the world where I used XML with the full security packages around the payloads (of XML) there was signing and encryption - the way to work was to peel the layers of the onion away slowly gaining greater trust as you proceeded into the payload. This works very well for confidential business messaging. I do enjoy the simplicity of JSON but is it too simple?