The core of WDDX is the XML vocabulary, and a set of components for each of the target platforms to serialize and de-serialize data into the appropriate data structure and a document type definition (DTD) that describes the structure of standard data types. Functionally, this creates a way to move data, its associated data types and descriptors that allow the data to be manipulated on a target system between arbitrary application servers.
WDDX is based on XML, which is a W3C Recommendation. Other W3C efforts now in the works will have obvious application to WDDX when they are completed, most importantly, the XML-Schema proposal. The WDDX DTD supports versioning, allowing these and other enhancements to be folded into the specification as they become available without disrupting working applications.