Some answers that may or may not be useful for the hardhats. Bill Walton wrote: > ----- Original Message ----- > From: "Greg Woodhouse" <gregory.woodhouse at sbcglobal.net> > To: <hardhats-members at lists.sourceforge.net> > Sent: 2006-04-10 10:46 AM > Subject: Re: [Hardhats-members] Software Archetypes - single vs double > systems > > > >> What I find most frustrating about discussion of archetypes is that it >> is so often vague and intuitive in nature, making it rather hard to >> decipher. >> >> --- Bill Walton <bill.walton at charter.net> wrote: >> >> >>> Software Archetypes - single vs double systemsHi Lorie, >>> >>> Archetypes provide a capability that's very familiar to programmers, >>> but take it to the next level. At the most basic level, it's about >>> decoupling. An RDBMS shields programs from the need to know about >>> the underlying structure of the data. A program needs only know >>> about the db schema. Views provide another level of abstraction, >>> shielding programs from changes in the schema. Archetypes (which I >>> believe do not depend on an RDBMS implementation) provide a similar >>> capability, but take it to the domain level. >>> >> By domain do you mean application domain? Or are you referring to >> domains in their technical sense in database theory (as a set of >> values)? application domain. It means you can consider an archetype as a model of some domain concept, like "microbiology test result", that a health care professional can understand (and define). >> At any rate, it is clear that you are trying to abstract away >> from a particular set of units, treating the quantity itself as a value >> (not how it might be represented). >> >> >>> When working with an archetype-enabled system, programs / programmers >>> work directly with domain concepts like blood pressure or height or >>> weight. The underlying data is stored / accessed through the >>> archetype. >>> >> But what does this mean? It suggests that an archetype is realizable as >> a computational object (much as a schema may be realized as a set of >> it is. The model of all archetypes is given at http://svn.openehr.org/specification/TRUNK/publishing/architecture/am/aom.pdf or if you want online UML, see http://www.openehr.org/uml/Browsable/_9_0_76d0249_1108467924943_474004_589Report.html >> relations, or a class instantiated to form an object). I suspect that >> this is the point at which an important concept is missing: The >> integers are a ring, but when I add two numbers, I'm not using the + >> operation of the category Ring, but rather of a specific member of that >> category, namely Z. >> >> >>> A trivial example of the benefits would be lbs. vs. kgs.. >>> In an archetype-enabled system, the program has no knowledge of the >>> unit-of-weight measure used to store the data. Programs access the >>> data store with statements like (no representation made re: syntax) >>> store_weight(220, lbs) and patient_weight = >>> retrieve_weight(patient_id, kgs). >>> >> Okay, here is some concrete syntax, but what are you really doing? Is >> kgs a flag or map (or something else altogether)? From a mathematical >> point of view, it's natural to think of it as a scaling transformation >> (a map). But that's confusing, too, because it implies the existence >> of some reference instance out there (say kilograms) that is somehow >> privileged among other possible choices, and that your kgs flag is >> simply the scaling factor (isomorphism) you need to apply to get your >> chosen representation. >> it is not that complicated. The archetype simply constrains a QUANTITY object which is defined by a QUANTITY class. The openEHR model of this class is here: http://www.openehr.org/uml/Browsable/_9_0_76d0249_1109599337877_94556_1510Report.html
There is a custom C_QUANTITY constrainer class that can be used as well, which is particularly suitable for constraining values in multiple unit systems. See this test archetype: 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 That's raw ADL of course; in the clinician's archetype editor it is done via a GUI. - thomas beale -- ___________________________________________________________________________________ CTO Ocean Informatics (http://www.OceanInformatics.biz) Research Fellow, University College London (http://www.chime.ucl.ac.uk) Chair Architectural Review Board, openEHR (http://www.openEHR.org)
