The HL7 Reference Information Model (RIM) and its Message Development Framework (MDF) and associated activities are very complex, specific, and as yet unstable. Together they constitute Version 3 of the HL7 standard, which is set to replace version 2 and its versions (Version 2.3 is widely used in New Zealand). They define a comprehensive set of inter-related concepts sufficient for the conduct of healthcare. The Medical part of the new RIM is The United Services Action Model (USAM), which is largely the work of GŸnter Schadow of the Riegenstrief Institute (aurora.rg.iupui.edu/~gunther/).
Version 3 is due to be published in December 2001. It contains all phenomena under the categories:
Acts
Participants
Entities (People, things, Places)
Roles
Relationship links
The USAM concepts collapse concepts and processes in 'actions', which come in a finite number of "moods" - Intent, Order, Event, Goal - are moods of an act.
All participants have some role in relationship to an act, and this fulfils, instantiates, or constrains the act. For message development you develop a model of the local context you are interested in, and map it to the Rim, which generate a 'refined message information model' (R-RIM), which is systematically related to what actually goes down the wire, including its temporal sequencing. These are complex, unusual, and difficult concepts that are nowhere yet well explicated (but see Curry, forthcoming), and still unstable.
The whole system is set up to work like one gigantic 'state-transition model' engine, and it is difficult to envisage from where we are now how we will engage with it. It is of some interest that Ed Hammond himself was very interested in the Health Event Summary concept, and suggested that other jurisdictions worldwide are as well, eg Taiwan. It could be that the HES will simply be expressed in the Common Data Architecture Template that HL7 are developing. However, it need not hold up local developments. The design and implementation of XML stylesheets can be made interoperable with whatever HL7 deliver in due course.