Often the schema of a clinical domain will be a superset of the VMR. For example,  this tutorial considers the situation of a diabetic foot clinic where additional information along with standard observations is recorded in the EHR and presentable through an extended VMR. The VMR extension can be captured in a  Package ( in a similar way to the way we did a Library). Its alos possible to import the new extended model as a 'hardwired' internal package.  Another way to customise an extended data model is to use an archetype.