xml.com features an interesting series on metrics for XML projects. So far most of the metrics focus on measuring XML schemas, not XML documents, but they are nevertheless worth reading:
I am Product Manager for Collaboration and Digital Asset Management at Day Software. (I was also one of the founders of Mindquarry and have contributed to some open source projects). In this weblog I am covering the impact of new collaboration models, of open source software and web technology to the information society, a world shaped by reason and productivity.