XML Schema is today's most popular schema language for XML, but it definitely is more a schema language than a modeling language. So when thinking about the abstract data model that should serve as the foundation for XML Technologies for Web-Based Publishing and Web-Based Services, it would be better to use a language which one the one hand was less XML-specific than XML Schema, but on the other hand would allow advanced content modeling for mixed content and semi-structured data in general. Such a language does not exist today, and the gap between XML and the modeling world is still considerable, resulting in hand-crafted translations which are hard to document and often lead to the models and the actual implementation diverging considerably over the lifetime of a data model.