XML has become a lingua franca for data exchange on the Web. When the XML standard was originally defined in 1998, its purpose was to define a common set of syntax rules that could be applied to multiple applications. XML isn't a language in itself, so much as it's a set of rules that define how markup languages designed for data representation should behave.
There have been a few attempts over the years to extend the XML recommendation and go beyond the original version 1.0, but each attempt has foundered. It's generally agreed that the rules of XML as they currently stand do what the standard should do, and each proposed addition has run into some sort of opposition.
The developer tools for working with XML, however, have continued to evolve. From the earliest XML processing APIs such as the Document Object Model (DOM) and the Simple API for XML (SAX), to more recent innovations such as JDOM for Java developers and the XML processing classes in the .NET framework, organizations that are responsible for creating programming languages and development platforms continue to improve the lot of developers who work with XML. The goal is always to make it as easy to parse and modify XML-formatted data as possible.
EcmaScript for XML (E4X) is one such toolkit. E4X was defined by Ecma International in the ECMA-357 standard and is implemented as a part of ActionScript 3. Any application running in Flash Player 9 or later has access to the E4X API and can use ...