Abstract

XML Schema is a document structure definition language making its way through the standards process of the World Wide Web Consortium. It's three headline requirements when chartered were:

* Deal cleanly with XML Namespaces;
* Provide a useful collection of primitive datatypes;
* Take advantage of up-to-date understanding of programming language design

In practice the last bullet means an OO type hierarchy which makes it easy to define new types in terms of old and to manage versioning of XML Schema documents.

I'll give an overview of the XML Schema language and where it sits in the overall XML story, and then concentrate on what the type system is like and how it could still use help from type theory professionals (which I'm not :-). At the end I'll say something about the bridge from theory to practice and how schemas may participate in XML's role for arbitrary application data transfer.