There's a great little article over on the O'Reilly network entitled Enforcing Association Cardinality. It's a good read for any UML followers out there looking to apply their knowledge within the realm of XML.

O'Reilly publish book on W3C XML Schema. O'Reilly and Associates have published XML Schema: The W3C's Object-Oriented Descriptions for XML, written by XMLhack's own Eric van der Vlist. [xmlhack]

Great! I hope more and more people get on board with schema based XML development. As I've mentioned before, I totally see the benefits in simple well-formed XML documents, but there's so much more power in terms of describing and consuming documents when using schemas.

As a side-note, if you don't already own a copy of Essential XML Quick Reference, I suggest you pick it up. It covers all of the major XML technologies in a concise, well indexed format.

Update: Thanks to John St. Clair who pointed out that the content for the quick reference is actually available for download at the DevelopMentor website. You'll need to sign up for a DM account, but it's painless and well worth it if you want the content.

Disclaimer: I could be considered biased because I reviewed the book, but honestly I use it almost any time I'm working with XML to look stuff up.