Thanks Rik. That was extremely useful. Its very interesting to see how HL7 has separated 'constraints' from the actual 'data'. It seems like templates (lets call them T) could be a set of cardinality constraints, value constraints, or terminology constraints, among other things. Except for the terminology constraints, its difficult to understand how the cardinality and value constraints are added to R separately. So what does the base data in R look like without the T info? Id think then that although theoretically the approach is very neat, in practice, however, T will always be a part of R. Can I assume R to be a CDA document? What other form in HL7 can R assume besides CDA docs?
Now assuming Im wrong and infact practically T is not always part of R (although T can be reused in several R's), is there a formal model to which T conforms structurally and semantically? In other words, structurally is there some RIM version specifically desgined to model T. Also semantically is there some sort of ontology that states that in this particular clinical scenario R needs to have these set of T? I finally seem to be getting ahead with my understanding of templates, so am very keen to go ahead with this discussion. Kind regards Rahil Rik Smithies wrote: >Hi Tom, Rahil > > > >>But I think your view of what the HL7 templates are is the closest Ive got >> >> >to receiving a clear explanation ! > >There has to be a better way to explain HL7 Templates than that. I'll give >it a shot. > >Consider that an HL7 model (an "RMIM") is analogous to an openEHR archetype. >It's a bunch of classes that represent healthcare data. > >When you start with an existing RMIM (call it "R") and create a list of >extra constraints upon it, that set of restrictions is a "template" on the >original model. > >A template in HL7 speak is therefore a set of constraints, and it can be >applied on top of model R or some other model. > >By constraint I mean things like: "only allow SNOMED", "only allow class A >and not class B", "allow max 2 of A". > >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. > >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. > >So what does an HL7 template look like? There is flexibility in how the >actual list of constraints is represented. > >It can be a diagram, itself pretty similar to an RMIM, or it can be a formal >document that makes a series of assertions that must be heeded. Techniques >have been developed to turn both of these into executable checks. > >In some cases these checks take the form of XSD, but it is not correct to >say that templates are in themselves XML schemas. You can also do the checks >with schematron, or any other validation technique you choose. > >Does that help at all? > >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. > >cheers, >Rik > > > >>-----Original Message----- >>From: openehr-technical-bounces at openehr.org >>[mailto:openehr-technical-bounces at openehr.org] On Behalf Of >>Rahil Qamar >>Sent: 07 December 2007 14:46 >>To: Thomas Beale >>Cc: For openEHR technical discussions >>Subject: Re: openEHR and CEN models >> >>Hi Thomas >> >>Thanks for the response. >> >>Thomas Beale wrote: >> >> >> >>>Depends on what you want to do ;-) >>> >>> >>Well we're looking at authoring openEHR Archetypes to seve as >>a standard form for representing clinical data for capture >>through templates (not the HL7 ones!). With people often >>confusing the openEHR approach with the CEN13606 work (and >>using them almost interchangeably), I wanted to make sure >>we're not going off on a tangent. >> >> >> >>>In the near future, the automatic bidirectional transformation for >>>openEHR/CEN will be completed (when CEN works out what data >>> >>> >>types it >> >> >>>is using). This will mean openEHR tools will be able to >>> >>> >>generate CEN >> >> >>>structures automatically. It may be worth looking at the >>> >>> >>openEHR EHR >> >> >>>Extract specification as well. This is not yet finished, but will >>>offer significantly more power than the CEN Extract, while >>> >>> >>containing >> >> >>>a CEN-like mode to act as a wrapper for CEN-encoded information. >>> >>> >>Ive downloaded the EHR Extract document. Just wanted to know >>exactly what this document will be beneficial for - are the >>Extracts to be used for sending relevant parts of the EHR >>data (or perhaps model) based on the user query? Does the >>document prescribe the format in which the extracts will be >>returned to the user or do they prescribe the query syntax or >>is it just a logical representation of how the Extracts >>relate to the EHR Information Model? >> >> >> >>>> In particular, is it important to know the CEN13606 archetypes if >>>>working with openEHR archetypes. At a logical level what are the >>>>differences between the two? >>>> >>>> >>>> >>>others may know better, but at the moment I don't know of any CEN >>>archetypes. >>> >>> >>Thats a useful piece of info. Ill look for more responses on >>this issue then. >> >> >> >>>>Another topic area that alludes my understanding is a clear >>>>parallel/possible relationship of HL7 Templates and the use of >>>>'templates' in openEHR archetypes (the later concept I am >>>> >>>> >>very clear >> >> >>>>about.. its the HL7 view of templates Im not sure of). It'll just >>>>help in my understanding of hl7 templates w.r.t. archetypes, as >>>>parallels are often drawn between the two. >>>> >>>> >>>> >>>We would like to know that as well ;-) What I know at this stage is >>>that an HL7 template is a specialised XML-schema of a base >>> >>> >>XML-schema >> >> >>>such as the CDA schema. There is no distinction in HL7 that >>> >>> >>I know of >> >> >>>between what we call archetypes and templates in openEHR. >>> >>> >>At the best, >> >> >>>you would have to say that an HL7 template is like an >>> >>> >>openEHR template >> >> >>>that is built like an archetype, i.e. no re-use of anything, just a >>>single giant archetype built for the particular purpose at >>> >>> >>hand (which >> >> >>>would normally make us call it a template...)... >>> >>> >>And I thought only I was confused :). But I think your view >>of what the >>HL7 templates are is the closest Ive got to receiving a clear >>explanation ! I had a guy show me how the Templates can be >>extracted from the CDA models .. at the end I was even more >>confused ! .. Ill revisit the hl7 templates work with this >>new understanding. >> >>Thanks a lot >>Rahil >> >> >> >>>- thomas beale >>> >>> >>> >>> >>> >>-- >>Rahil Qamar >> >>Ph.D. Student >>Medical Informatics Group >>Room 2.43 Kilburn Building >>University of Manchester >>Work number: +44 (0) 161 275 6151 >>Email: qamarr at cs.manchester.ac.uk >>Website: http://www.rahilqamar.com/ >> >>_______________________________________________ >>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. >If you are not the intended recipient please accept our apologies. >Please do not disclose, copy or distribute information in this e-mail >or take any action in reliance on its contents: to do so is strictly >prohibited and may be unlawful. Please inform us that this message has >gone astray before deleting it. Thank you for your co-operation. > >NHSmail is used daily by over 100,000 staff in the NHS. Over a million >messages are sent every day by the system. To find out why more and >more NHS personnel are switching to this NHS Connecting for Health >system please visit www.connectingforhealth.nhs.uk/nhsmail >********************************************************************** > > > > -- Rahil Qamar Ph.D. Student Medical Informatics Group Room 2.43 Kilburn Building University of Manchester Work number: +44 (0) 161 275 6151 Email: qamarr at cs.manchester.ac.uk Website: http://www.rahilqamar.com/ -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.openehr.org/mailman/private/openehr-technical_lists.openehr.org/attachments/20071207/a197098e/attachment.html>
