The best current examples of what a "VMR" is, is in the GELLO R2 standard. In this it defines the EHR interface that GELLO talks to, to query a patient's medical records.
Datatypes are in accord with ISO 21090.
It is a "Virtual" interface and is optimised for point in time clinical decision support and while it could be used as the basis for an EHR design it is intended to be simplified, to represent a snapshot and to omit important concepts that should exist in a real EHR.
In particular concepts such as audit trail, result history and display forms are omitted and only data relevant to making decisions based on the current patient state are represented. The hard bit is excluding as much complexity as possible while ensuring that any decisions made are safe and based on adequate data.
The aim is to allow GELLO or another CDS language access to a standard model to reliably access patient data about the current patient's "Observations" (eg haemoglobin) or "Family History" or eg "Surgical History"/"Problem List". This is the single patient "Context" but other contexts are relevant. Access to population based data is very important for public health monitoring (perhaps context "Population"?) and in the case of templates access to data during the editing process (context "Template").