Versioning and extensibility in XSD

Dare has a new article on designing XML dialects that are both versionable and extensible, a topic I've spent quite a bit of time on in my own work. Dave Orchard had a similar piece a while back too. Both are worth reading to understand the issues. Both end with approaches to schema design that make clear an ugly truth: the need for determinism in XSD (WSX) makes describing the natural and intuitive approaches to extending and versioning XML documents impossible. Rather, we are forced to adopt constructs with either sequential or hierarchical delimiters to ensure XSD (WSX) determinism. As a side-effect, we have to create convoluted instance documents that are harder to read and write. In a better world, we wouldn't have to sacrifice simplicity to get the loose-coupling that versioning and extensibility provide.