The promise of XML was to be a metadata-rich and self-describing data storage format, although most people actually _producing_ XML ignore this (as anyone who has had the pleasure to do a CVS merge on the XML generated by Websphere Studio will attest to). This also leads to the fact that most XML-based programming languages end up looking like a poor imitation of Lisp.

XML has essentially become a way of serializing object hierarchies and sending them as data back and forth between services. the 'self-describing' PromiseOfXml has been sort of lost in the shuffle.

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