ActionScript 3.0 includes support for E4X – ECMAScript for XML. A reminder: ActionScript is part of the ECMAScript family standard.
“ECMAScript for XML (E4X) offers new ways to retrieve data from XML in Adobe Flash applications. (…) you can use E4X to fetch data out of an XML object within an application in real time—processing only the information required to run the application.” (Adobe)
A link to an Adobe E4X tutorial:
http://www.adobe.com/devnet/flash/articles/filtering_data_e4x.html
ECMA’s E4X page:
http://www.ecma-international.org/publications/standards/Ecma-357.htm
Wikipedia’s E4X page:
http://en.wikipedia.org/wiki/E4X