It looks like in the Xml Diff Specification* the authors chose to implement their own path-like language for locating nodes in Xml Documents. Does anybody have any idea why (asie from the obvious desire to create wonderful new things) why they didn't use good ole' W3C standard XPath? I can't see any example expressions that couldn't be written in XPath.
* This was released in 2002. For those who only like cool, new, shiny things this is none of those. Go back to imbedding workflows in XAML UIs which you can call from Atlas via your Indigo ServiceBroker channel.