Rik Smithies wrote: > Hi Tom, Rahil > > Templates are a neat way to foster re-use of R, because they package up all > the refinements and improvements you may want on R, but only those extra > rules need be in the template - just the differences. You don't put the rest > of R in there. > this approach to representation is what is used by openEHR archetypes and templates although in slightly different ways. > Hence you don't need to keep cloning R over and over in order to re-use it > with just slight variations. That would proliferate objects and give you a > maintenance headache. > But this only gives a basic level of re-use - reuse of the whole RMIM. > As far as I'm aware there is no HL7 equivalent of openEHR templates (and I'm > not sure there is an openEHR equivalent of what HL7 calls templates either). > An HL7 template is a "model of constraints" that goes along with another > model. > > well, that's what an archetype is, and a template is. But the semantics are different. The set of constraints in an archetype are constraints for representing content to do with a particular topic, regardless of contextual use. Such as BP measurement, diagnosis, etc. This provides a level of definition where clinicians can define how to record all data points to do with a particular subject, regardless of where such data points might need to be recorded in the business process.
OpenEHR templates provide a way to combine and further constrain the data points expressed in archetypes, in chunks or groups corresponding to context of use, i.e. screens, reports or some other grouping that correspnds to a business process step. There are many forms for example that will capture vital signs, so you need a place to define all the data points of the vital signs - the archetypes. The reason HL7 doesn't do this is because the RMIM is already dedicated to a particular topic, like lab observation or whatever. However, unlike in openEHR, an RMIM is a new schema, 'derived' from the RIM - but nevertheless a new schema. In HL7 speak, it is a data 'projection', i.e. a selection of certain attributes from various classes in the RIM, plus cloning. So HL7v3 is constructed as follows (simplifying the DIM/RMIM/CMET business): 1 RIM -> N derived schemas (RMIMs) -> M templates per RMIM. i.e N systems of 1 schema + M templates. openEHR is constructed as: 1 Reference Model -> N archetypes -> M templates, which are N:N with archetypes (but more numerous). This gives a system with a single schema - the reference model - and 2 further levels of constraining which allow topic-based deifnition and then context/business event specific definition. But in the end all the information is just instances of the reference model; in HL7, each message (RMIM) has its own instances, because each is a different schema. - thomas beale * *
