From OpenWDDX.Org:
"The Web Distributed Data Exchange, or WDDX, is a free, open XML-based technology that allows Web applications created with any platform to easily exchange data with one another over the Web."
"WDDX is an XML-based technology that enables the exchange of complex data between Web programming languages, creating what some refer to as 'Web syndicate networks'. WDDX consists of a language-independent representation of data based on an XML 1.0 DTD, and a set of modules for a wide variety of languages that use WDDX. WDDX can be used with HTTP, SMTP, POP, FTP and other Internet protocols that support transferring textual data."