Andrew The lab result is a good example of further constraining and it is really additional constraints. It is just that the at0013 (any data type) is labelled and turned into a quantity with units. It looks like extention but is it further constraint in this instance.
However, we do extend archetypes - as Kerry says - as long as there are no surprises at runtime this is OK. So all the paths in the parent must do what they do in the parent. Cheers, Sam > Hi Grahame and Health, > > It seems that Sam is working by a philosophy of extension in his archetypes. > For example, take lab result, which is an entry level archetype that has a > list of coded result values. The lipids labs result archetype seems to > extend the existing archetype by create new fields for cholesterol, > triglycerides, etc, rather than further constraining the existing coded > result values in the lab result archetype. > > I am not sure specialization by extension is applicable to the archetype > specialization case. Archetypes works by constraining the reference model. > Therefore, any further specializations of an archetype may only further > constrain what the parent archetype supports. For example, the lipids lab > result archetypes should have further restricted the lab result archetype to > have contained coded fields for cholesterol, triglycerides, etc. > > -Andrew > > > > > > -----Original Message----- > From: owner-openehr-technical at openehr.org > [mailto:owner-openehr-technical at openehr.org] On Behalf Of Grahame Grieve > Sent: Thursday, 26 May 2005 2:21 PM > To: openehr-technical at openehr.org > Subject: Re: The semantics of archetype Specialization > > Hi Andrew > > If the language only makes positive structural statements, > such as standard 3gl o-o paradigms, then specialization > cannot be done by restriction - while there's nothing > stopping it, there's no way to express it. (Though > reference Heath's email - there's various ways to > actually do it, but many of them result in ill-formed > models, just the compiler doesn't know how to stop them, > therefore they are "legal") > > If the language is able to make constraint statements, > then specialization can be done by both restriction and > extension - but restrictions in the generalization will > prohibit some forms or instances of both extension and > restriction in the specializations. > > ADL is able to make both positive structural statements > and constraint statements, so it's able to support > specialization by extension and restriction. > > But I think, due to the nature of ADL, that there is > no computationally provable answer to whether any given > specialisation is properly formed (at least in the > general case). > > Many of the stupid things about XML Schema > arise because they have a requirement (I think), that > there must be a computationally provable answer. > > Grahame > > Andrew Goodchild wrote: > >>I would only hope that that is what is intended. However, the semantics at >>the moment that appears to be supported by the editor implies that > > archetype > >>specialization is nothing more that "cut and paste" style semantics. We > > will > >>have to wait for the answer from Tom and Sam. >> >>Also, I am wondering if archetype specialization only supports restriction >>or extension or both? >> >>-Andrew >> >> >>-----Original Message----- >>From: owner-openehr-technical at openehr.org >>[mailto:owner-openehr-technical at openehr.org] On Behalf Of Grahame Grieve >>Sent: Thursday, 26 May 2005 12:08 PM >>To: openehr-technical at openehr.org >>Subject: Re: The semantics of archetype Specialization >> >>Hi Andrew >> >>Well, I'll defer to Tom or Sam. But from a >>computational perspective, what else could make sense? >> >>Grahame >> >> >>Andrew Goodchild wrote: >> >> >>>Thanks Grahame, >>> >>>The UML specs definition of specialization matches what I thought it had >>>meant. >>> >>>I guess what I would like to understand is whether such a definition is >> >>true >> >> >>>or not for archetypes? >>> >>>Is specialization in archetypes meant to support the definition you >> >>provided >> >> >>>and the archetype editor is missing some functionality to ensure that only >>>correctly specialized archetypes can be built? >>> >>>- or - >>> >>>Is it that archetypes and the editor supports some new semantics around >>>specialization that I don't quite understand yet? >>> >>>I am sure Sam or Tom could shed some light on this ... >>> >>>Cheers, Andrew >>> >>> >>>-----Original Message----- >>>From: owner-openehr-technical at openehr.org >>>[mailto:owner-openehr-technical at openehr.org] On Behalf Of Grahame Grieve >>>Sent: Thursday, 26 May 2005 10:57 AM >>>To: openehr-technical at openehr.org >>>Subject: Re: The semantics of archetype Specialization >>> >>>Hi Andrew >>> >>> >>> >>> >>>>Does anyone know what it actually means to specialize an archetype? And >>> >>>what >>> >>> >>> >>>>the rules are? >>> >>> >>>The UML specification offers this definition for generalization: >>> >>> A taxonomic relationship between a more general element and a >>> more specific element. The more specific element is fully consistent >>> with the more general element and contains additional information. An >>> instance of the more specific element may be used where the more >>> general element is allowed >>> >>>I think that this is a fairly watertight definition and quite relevent >>>to your question. >>> >>> >>> >>> >>>>I looked at the archetype editor and created a specialized archetype of >>>>another. The editor seemed to just copy the parent archetype and then >>>>allowed the user to change anything about the archetype. >>>> >>>>For example, I can now make a mandatory field optional, or I can extend a >>>>parent archetype with new mandatory fields that don't exist as optional >>>>fields in the parent archetype >>> >>> >>>By the UML definitions, these become "ill-formed" model. >>> >>>Of course, it's one thing to to state the definition, quite another to >>>know how to compute whether a model is ill-formed. >>> >>>Grahame >>> >>> >>> >>>- >>>If you have any questions about using this list, >>>please send a message to d.lloyd at openehr.org >> >> >> >> >>- >>If you have any questions about using this list, >>please send a message to d.lloyd at openehr.org > > > > > - > If you have any questions about using this list, > please send a message to d.lloyd at openehr.org > - If you have any questions about using this list, please send a message to d.lloyd at openehr.org
