For tabular data storage of complex data types, an array of structures should be used. Because some of the languages supported by WDDX are not case-sensitive, no two field names can differ only by their case. Null values- WDDX provides no notion of a null object. Null objects should be serialized to empty strings. Upon deserialization it is up to the component performing the operation to determine whether and where should empty strings be deserialized to null values.
Null support is one area where future extensions are likely.
WDDX serializes data using a model of pure aggregation. It has no mechanism for handling object references. Aliased references will result in multiple object instances being deserialized. Object references support is another area of potential future investigation. This DTD is purposefully made verbose to aid the readability of WDDX packets.