Link: http://www.stylusstudio.com/xml_differencing.html
Source Author or Organization: Stylus Studio

Stylus Studio provides an integrated XML Differencing tool for visually comparing and analyzing any changes made to XML files or folders in a configurable, XML-aware fashion. A streaming video demonstration entitled: Using XML Differencing in Stylus Studio explains how it works. The XML Differencing utility lets you step through changes one at a time in either a tree view or merged text view. Common XML differencing options include: Ignore whitespace, compare XML namespaces, expand DTD entity references, ignoring formatting characters, XML comments, XML attributes, processing instructions, etc.