In future architecture form the RHIE project the use of more standardised message format will be explores. Particular the use of IHE profiles to enable components to be more loosely coupled and to conforms my closely to international standards. This is in line with the current OpenHIE thinking.
The following page on the OpenHIE wiki shows of the latest thinking in term of the profiles that could be supported: https://wiki.ohie.org/display/documents/OpenHIE+Architecture+-+IHE+profiles+for+coordinated+communication