The original documentation, written before the code, has a good overview of the motivations and design decisions.
http://junom.com/document/tWSDL/api-types.html
Also, the XML API (now in ::xml, not ::wsdl) is explained here along with discussion of tDOM usage. The examples are no longer completely accurate, but they are very close. Considering these docs were written almost two years ago, it is surprising how close the final code came to the plans.
http://junom.com/document/tWSDL/api-xml.html
The main difference is the addition of prefix information into the metadata along with the ability to add child elements by reference (instead of actual namespace children). Also, all of the XML elements are created through a single API. This frees future developers from needing to know the bookeeping details for element metadata, and any changes to the internal details will not affect any developer code.
The next development push will probably be to add support for attributes. That means the ability to define them either globally or locally, associate them with any global simpleType, and include them in document validation. Attribute validation and defaulting should be much easier than what is required for element validation. Internally I intend to use attributes to indicate information about the element content, for instance if/how the content is encoded.
