Hi Rahil >Except for the terminology constraints, its difficult to understand how the cardinality and value constraints are added to R separately. yes, that was the tricky bit ;-) You end up with 2 models, and need a way to apply one model on top of another. The tools you use to validate that you have an R can be modified to validate that it is also an R+T. Once you realise that R and T are both actually constraints of other models you are there. >So what does the base data in R look like without the T info? R already has lots of assertions and constraints in. R stands alone, and may exist for years before T comes along. (I'm assuming you mean the model data, rather than the instance data.) >Can I assume R to be a CDA document? What other form in HL7 can R assume besides CDA docs?
Yes R is commonly CDA, but R can be any model. In less widely used models than CDA, repeated re-use may not be so much of an issue. If you are the only people to use R you may just make a model R2 is that is a clone but with more constraints modelled right in it, and stop there, no need for T. >What other form in HL7 can R assume besides CDA docs? T could be a template on the Clinical Statement model, and then it could be applied to models based on that pattern. It is true that any fairly complex T will be closely bound to R. An assertion always has a context. Finding the right granularity of re-use is hard in any domain, but some constraints could be very simple and could apply to various models. >structurally is there some RIM version specifically desgined to model T. T can only assert things that are allowed in HL7 of course. R+T must be a valid model. There is no other base model for T than the RIM. But T isn't really RIM stuff, its more "constraint on RIM stuff". "Cardinality <= 2" isn't in the RIM of course, it's something that applies to a RIM based model. I suppose I should stress again that there is no new RIM here, no new reference model, its just that there are multiple RIM-model instances or RIM-constraints applied together. All the bits that make up templates already exist, it's just a new application of them, and maybe some modified tooling. >Also semantically is there some sort of ontology that states that in this particular clinical scenario R needs to have these set of T? Not an ontology perhaps, but is is getting common for people to start with some R and make a series of templates that need to be used (by their requirements) when using R in a certain clinical domain. NHS CFH for instance have some 50 odd templates that they use in various combinations on CDA to create CDA flavours for a half dozen or so domains. glad to help, Rik _____ From: Rahil Qamar [mailto:[email protected]] Sent: 07 December 2007 16:32 To: rik.smithies at nhs.net Cc: qamarr at cs.manchester.ac.uk; 'For openEHR technical discussions'; 'Thomas Beale' Subject: Re: openEHR and CEN models 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: [email protected] [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/ ********************************************************************** 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 ********************************************************************** -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.openehr.org/mailman/private/openehr-technical_lists.openehr.org/attachments/20071207/8a98de2c/attachment.html>
