Uche Ogbuji writes in response to my remark about XML. Mainly he's concerned about the conflation of XML and WS*.
I would list something more serious... usage models. XML is just a notation. I agree WS* and XML are relatively distinct topics. But XML is used to represent everything from SOAP messages to config files to databases, and it's not particularly good at any of them.
What does it mean to perform an XML query, when XML is just a notation and not a model per se? There is no "there" there when it comes to what an XML model is. XML is a notation for expressing essentially *any* kind of model.
So worse than conflating XML and WS* is the notion that XML is a model of some kind.