Hi Tom, bit tardy getting back to this thread I'm afraid, but just to come back on a couple of those points:
> well - one of the main functions of a template is to choose > what is needed from the archetypes. Let's say a template > 'assembles' 5 archetypes each with ... > 50 possible data points...then the total potential > number of data points is 250. But the template might choose > just 10, say 2 from each archetype, according to the needs of > the business process step corresponding to the data capture > being modelled by the template. That?s fine, you can build one model from others in V3 modelling. Once you can constrain one model to another, and build models out of others, you can do what you like. HL7 just doesn?t have two well established words for the small bits and the big bits, or the constraining down and the assembling back up. Maybe the granularity differs a little too. > yes, but the semantics of each such variant class are > different from the parent - various attributes have been > removed etc. The semantics of the variants aren't really different though. If you can cope with an A that has an optional property X that is any?code, you can cope with a constraint to B that is mandated to always have an X that is always "123". In particular, the fact that is has a new name 'B' adds no semantic meaning at all. It's really just a nameless "classCode=OBS, code=123". HL7 templates don't add semantics to instances either. The template (or any model) is just a specification of what you want to be assembled as the data elements. The XML doesn?t say "this is a BP template, and you need to go and look up what that means". The template just says "when creating a BP, do it like this (and we'll know if you don?t...)". The template is useful because it can show illustrate to people that a BP is made up of systolic and diastolic and other stuff. So people know what to build, or what to collect on a screen. But they don?t put a template in the instance. They put observation classes in it that happen to match what it says in the template. > so a single HL7 template might only have the scope of a > single (variant) class inside an RMIM? Absolutely. Any model can be a template, and a model can one or a hundred classes. Non graphical templates can be a single assertion (though they aren't the main trust of this thread). Actually, reading again, I think you may possibly mean: can a template can be applied to a single class in an RMIM? You can do that also. A template can be any size and be applied at any point on another model. cheers, Rik > -----Original Message----- > From: openehr-technical-bounces at openehr.org > [mailto:openehr-technical-bounces at openehr.org] On Behalf Of > Thomas Beale > Sent: 12 December 2007 11:01 > To: 'For openEHR technical discussions' > Subject: Re: openEHR and CEN models > > > Hi Rik, > > Rik Smithies wrote: > > > > HL7 models can and commonly do have this level of granularity. > > > > What are generally called RMIMs perhaps typically don't, > but a small "RMIM" > > model could be just such a BP measurement - a component in other > > words. It would generally be called a CMET or template but > the model > > is exactly the same despite the name. > > > > These components are assembled into other models (which > would perhaps > > be called full RMIMs, but could be other templates or > CMETs), and this > > seems like the assembly of archetypes into openEHR templates. > > > well - one of the main functions of a template is to choose > what is needed from the archetypes. Let's say a template > 'assembles' 5 archetypes each with (for the sake of example) > 50 possible data points (note that even the BP archetype can > generate 100s of data points), then the total potential > number of data points is 250. But the template might choose > just 10, say 2 from each archetype, according to the needs of > the business process step corresponding to the data capture > being modelled by the template. > > > > > > This is obviously true to a degree since any HL7 model has a unique > > validation schema that checks that an instance or a > fragment conforms. > > > > But all models are actually expressed in the single RIM > schema, since > > even in instances, where you can have unique class names (eg > > ObservationSystolic, > > ObservationDiastolic) the RIM class is indicated via > structural codes > > eg "classCode='OBS'". > > > yes, but the semantics of each such variant class are > different from the parent - various attributes have been > removed etc. I had all this explained to me a year ago by > Gunther Sshadow in no uncertain terms - hsi explanation was > that each such variant class is a 'projection' on the RIM > parent class, which contains all possible attributes (aka > columns) needed by that class. So any variant 'class' is > actually more like the SELECT a,c,e,g part of the SQL > statement SELECT a,c,e,g FROM Observation, where we assume > that Observation is a table/class with columns/attributes > a,b,c,d,e,f,.... Needless to say, such semantics pose all > kinds of problems for object-oriented software engineering > (having to know all the properties of a superclass in > advance, for a start). > > HL7 templates can be applied to these uniquely named classes even > > though the template has different class names (in fact normally the > > RMIM has the plainer names, and the graphical HL7 template > the specialised ones). > > > > Templates are thus not tied to single RMIMs and so not to a > single topic. > > > so a single HL7 template might only have the scope of a > single (variant) class inside an RMIM? > > - thomas > > > _______________________________________________ > openEHR-technical mailing list > openEHR-technical at openehr.org > http://lists.chime.ucl.ac.uk/mailman/listinfo/openehr-technical > ********************************************************************** This message may contain confidential and privileged information. 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