This is the response I sent to one list on this topic... I don't feel so bad with this large size post, since I already have to compete with Greg;-) The following looks technical, but if you have the patience to follow the links, most people should get it (having 2 screens like I do nowdays helps!).
I'll have to go through the maths below when I have a little more time, but it isn't the basis for archetypes as such (there might be congruencies). The formal basis (as it turns out) for the constraint part of an archetype is Frame logic queries. These are passingly described in Michael Kifer's Frame Logic paper of 1995. However, we also combine an ontology and interpolation of coded terms into the archetype nodes to give them meanings beyond the meanings possible purely from the underlying class model. If you have a look at an example archetype like a simple goal archetype: human readable HTML expression: http://oceaninformatics.biz/archetypes/openEHR-EHR-EVALUATION.goal.v1.html ADL computable expression: http://oceaninformatics.biz/archetypes/ADL/openEHR-EHR-EVALUATION.goal.v1.adl You can see that in the ADL expression in the "definition" section a lot of statements of the form TYPE_NAME matches {} and attribute_name matches {}. These define the instance spaces of objects (conforming to TYPE_NAME) in terms of the instance spaces of their attributes, recursively. All the TYPE_NAMEs and attributes names are from the reference model (in this case, the underlying model is the openEHR reference model, see http://svn.openehr.org/specification/TRUNK/publishing/architecture/computable/UML/uml_start_view.html) <http://svn.openehr.org/specification/TRUNK/publishing/architecture/computable/UML/uml_start_view.html%29> The whole definition section is a constraint statement, defining a boundary in the instance space of the outermost type, in the case of this example, EVALUATION (see http://www.openehr.org/uml/Browsable/_9_0_76d0249_1109249648736_872559_12384Report.html). <http://www.openehr.org/uml/Browsable/_9_0_76d0249_1109249648736_872559_12384Report.html%29.> Now, since there is a lot of optionality in archetypes (0..1, 0..* etc), an archetype actually defines a family of boundaries in instance space. This is similar to an F-logic query, because it acts like a filter - you apply it to a database, and if you find instances "inside" the boundaries, you have found something that "matches" the query. Note that the use of coded terms to give nodes domain-level meaning multiplies up the possibilities vastly. (What I mean by this can fairly easily be understood by looking at http://my.openehr.org/wsvn/knowledge/archetypes/dev/adl/openehr/ehr/entry/observation/openEHR-EHR-OBSERVATION.blood_gases.v1.html?op=file&rev=0&sc=0 <http://my.openehr.org/wsvn/knowledge/archetypes/dev/adl/openehr/ehr/entry/observation/openEHR-EHR-OBSERVATION.blood_gases.v1.html?op=file&rev=0&sc=0> - in this archetype, if you get down into the middle of it, you will see the type name ELEMENT and CLUSTER a lot; just after each reference, you see a code in []; the corresponding meaning of the code in English is given in teh comment at the end of the same line. So you can see that the "meaning" of the ELEMENT with [at0004] is "PaO2", whereas the ELEMENT with [at0005] is "PaCO2".) Now, given this, what can be said about a detail like units in quantities is the same that can be said about any detail: it depends on what is in the reference model. In the openEHR reference model, the part that models Quantity is here: http://www.openehr.org/uml/Browsable/_9_0_76d0249_1109599337877_94556_1510Report.html You can see that in this model it is the class DV_MEASURABLE that adds units. The most common type of thing with units is a DV_QUANTITY. Now here is a test archetype constraint QUANTITYs (we don't bother with the DV_ in archetypes - this is just a cosmetic thing): http://my.openehr.org/wsvn/knowledge/archetypes/dev/adl/test/clinical_types/adl-test-entry.c_quantity.draft.html?op=file&rev=0&sc=0 <http://my.openehr.org/wsvn/knowledge/archetypes/dev/adl/test/clinical_types/adl-test-entry.c_quantity.draft.html?op=file&rev=0&sc=0> You can see that the first attribute of SOME_TYPE, called standard_quantity_attr, constrains a QUANTITY to be either >= 4oC or >=40oF. There are other alternatives as well, as you can see below that. he explanation of how this works is too long to go into here, but is in the ADL manual (http://svn.openehr.org/specification/TRUNK/publishing/architecture/am/adl.pdf). <http://svn.openehr.org/specification/TRUNK/publishing/architecture/am/adl.pdf%29.> A real archetype full of quantities was the blood gases one from just above. Now if anyone is still with me, the next thing to say is that archetypes are completely generic with respect to object models, so constraining things like units is no different from constraining anything else; it depends on what you put in the object model to be constrained. As far as units go, you can see in archetypes like http://my.openehr.org/wsvn/knowledge/archetypes/dev/adl/openehr/ehr/entry/observation/openEHR-EHR-OBSERVATION.cbc.v1.html?op=file&rev=0&sc=0 <http://my.openehr.org/wsvn/knowledge/archetypes/dev/adl/openehr/ehr/entry/observation/openEHR-EHR-OBSERVATION.cbc.v1.html?op=file&rev=0&sc=0> that a "en-us" translation would most likely add in a few unit additions, to allow for SI and non SI, e.g. for concentrations etc (actually, I don't think this is cleanly a US/non-US thing, most of these kinds of analytes are measured in a metric fashion everywhere, but there are different variants like mks and cgs, and other details like moles versus g/l etc). Following are some starting links for archetypes: - mind map entry: http://oceaninformatics.biz/archetypes/MindMap/ArchetypeMap.html - search engine: http://www.dualitysystems.com.au/archetypefinder/archetypefinder - static page with human readable HTML and ADL archetypes: http://oceaninformatics.biz/archetypes/ hope this demystifies a few things.... - thomas beale ------------------------------------------------------------------------ YAHOO! GROUPS LINKS * Visit your group "openhealth <http://groups.yahoo.com/group/openhealth>" on the web. * To unsubscribe from this group, send an email to: openhealth-unsubscribe at yahoogroups.com <mailto:openhealth-unsubscribe at yahoogroups.com?subject=Unsubscribe> * Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/>. ------------------------------------------------------------------------
