Updated data model again, as a fallback point before I add some relationships.  Last time I tried Xcode gave me some errors and I had to revert to an earlier version.
Basic structure of data model is complete.  Future changes should mainly be to the attributes and unforeseen entities.  Simple mapping to HL7 RIM should be possible with this model.
Cleaned up the navigation.  The outline of navigation is now in place and has been implemented against the BitSalve Mockups V2 document which makes use of the tab bar on the patient home screen.