On 10/04/2013 13:33, Tim Cook wrote:
> [reposted for Tim; hist original bounced]
>
> On Wed, Apr 10, 2013 at 5:14 AM, Thomas Beale
> <thomas.beale at oceaninformatics.com> wrote:
>
>> it's similar, but misses the crucial distinction between archetypes and
>> templates. Without that there is no library of re-usable concepts to use in
>> your data-set definitions. As far as I can tell, this distinction just
>> doesn't exist in MLHIM. So it means that every 'model' has to make up its
>> own definition of standard items like vital signs, lab analytes and so on.
>>
> MLHIM allows reuse but does not allow redefinition. Redefinition of a
> component after it has been used to generate instance data is a BAD
> THING. You are simply looking for trouble when models can morph into
> something they were previously not. Then we can discuss the
> complexity managing that process. It just isn't necessary in MLHIM.
A couple of things to say here. 'Redefinition' as in openEHR and most
model-based systems I know of doesn't mean you change something that has
been deployed. It means being able to specialise an existing model in
the design environment, in a similar way as in object-oriented
programming. So the point is to be able to re-use and adapt existing
definitions, not just 'use' things.
Not being able to do this means either:
* you are stuck using someone else's definition, and you just live
with not having the bits you wanted
* you have to make a copy, and rewrite to suit yourself. Now you have
a different model, technically unrelated to the original, and tools
have no idea that they might be able to query for some of the same
data points.
There is actually no such thing as 'redefining a deployed model'. Models
can be evolved over time, and they get new version numbers. Breaking
changes get new major versions, which are treated as distinct models in
archetype land.
But new versions with non-breaking changes can be treated by querying,
modelling tools, reporting etc as being compatible with earlier
versions. Being able to query safely over longitudinal data whose models
change over time is essential in health.
It's clear that these needs (specialisation of models, longitudinal
querying over data) are seen as essential by large orgs, e.g. the CIMI
members Mayo clinic, InterMountain Health, Veterans Health, Nehta and so
on. The OHT Model-driven Health Tools (MDHT) project is founded upon
concepts like model specialisation and re-use.
I don't think there is any way these needs can be ignored in a scalable,
adaptable health information modelling ecosystem.
- thomas
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