Some classes in the reference model require specific expression in the graphical user interface (GUI). Those that are 'locatable' and have a name such as SECTION and CLUSTER can be dealt with generically as they are labeled containers, others such as the ITEM_STRUCTURE classes are expressed in most environments generically (such as the ubiquitous TreeView control). Classes which require particular handling in the GUI are:

• The [COMPOSITION] class which is the container for all things committed to the EHR and corresponds to the idea of a document
• The [ENTRY] classes including:
  • ACTION for recording what has been carried out
  • EVALUATION for recording summary information or opinions
  • INSTRUCTION for things that are to be done and when
  • OBSERVATION for things that are expressed or measured. This will include expression of its [event classes]]:
    • POINT_EVENT for a point in time, and
    • INTERVAL_EVENT for data covering a period of time
• The ELEMENT class or leaf node which has data values.