Hi guys,
Maybe we can help.
As David and Sam know I’m working on archetypes too and for now I’ve created my very simplified version in an XML format that is converted back and forth in David’s OpenEMed COAS server. I’ve gone one step further and added a front-end using the Apache Cocoon webapplication framework which is based on XML and XSL transformations. This results in a generic EHR system that we have tested with a small group of users in the CVA-domain. We also tested how generic it is, by implementing two other domains (AML patients in the hematology dept. and registration of MRSA infections) and proved to be succesful.
So I have some knowledge of OpenEMed AND Archetypes and ADL and XML and XSL and a little bit of XML Schema. 
On the other hand: my coworker and roommate is involved in the definition of HL7v3 DMIM/RMIM and messages for various aspects of the primary care domain. These XML messages all validate against extensive XML Schema’s so we had our share of schema problems.
I must confess I don’t follow the OpenEHR lists very closely, but this caught my attention and it’s nice to see familiar names.
I would very much welcome ADL expressed in XML and XML version of properly defined archetypes. I too prefer Java to keep things cross-platform. And both OpenEMed and Cocoon are written in Java, so that made the choice of programming language easy for me.
Sorry for the rambling, but I’d very much like to see archetypes get beyond the theoretical state and into working, preferably open source, projects.
Bye, Helma