On 02/04/2018 10:59, Philippe Ameline wrote:
Le 01/04/2018 à 14:13, Thomas Beale a écrit :
just by means of clarification for some readers, since I happen to
know how both openEHR and Philippe's system works, here's the way to
understand how openEHR would perform the same function as
Ligne-de-vie (which it can):
* build a lot of CLUSTER archetypes, and probably more OBSERVATION
ones; each CLUSTER archetype would be one of the 'trees' Philippe
talks about
* each of those CLUSTER archetypes has slot nodes that indicate
where subordinate CLUSTER archetypes join, and which ones are
allowed, in the usual openEHR fashion;
o remember, a slot can allow multiple possible substitutions
* at run time, a form containing a top level Entry, usually an
OBSERVATION will be deployed on the screen, and by a process of
user choice / UI movements etc, the data will get filled in, and
subordinate CLUSTER archetypes will be chosen on the way, and
filled in along the way.
This mode of operation is known by us in openEHR-land as 'dynamic
slot-filling' or 'runtime templating', as opposed to the more typical
design-time templating used in a lot of systems, where most of the
choices are made prior to runtime. But openEHR systems do use runtime
slot-filling as well, e.g. for writing discharge summaries and
referrals, where the data items are only knowable in the encounter or
report-writing session.
This trend allows me to discover that openEHR already became a rich
ecosystem. Isn't this technique close from Gerard's vision of
archetypes as "context for concepts" in a kind of ontology?
However, I probably wrongly expressed what I wanted to say, and is
more theoretical than comparing implementations, such as openEHR and
Ligne de vie.
When we talk to one another using a natural language, we just need a
vocabulary and a grammar. The grammar is simply a set of rules, but
not a physical pattern. We say "John sees the green house" and not
"John as the subject sees as the verb the green as an adjective house
as a noon in a position of direct object complement".
In the same way, it is possible to express a structured discourse just
using an ontology and a grammatical structure (say trees) without the
need of any structure description.
you are I think using 'grammar' in an unusual way - normally it means
the set of production rules that define legal utterances in some
language; this is an intensional definition, i.e. it can be used
computationally to parse actual utterances (including garbage) and
generate structures only for the utterances obeying the rules of the
grammar.
In your usage, 'grammar' is what you call the trees, which are
extensional maps of legal utterances, or fragments of utterances, which
can only be connected together according to their rules, which ensure
correctness of larger utterances, e.g. a colonoscopy report.
Structurally and computationally then, the fils guides (the trees in
Ligne de Vie) and archetypes are the same; they differ only in
representational details. However, there are two semantic differences.
Firstly, the fils guides depend completely on the ontology (which is an
ontological terminology, to give it a more correct name, I think), and
the two things are built as a combined representational system. Whereas
elements in archetypes can have bindings made to ontologies and/or
terminologies, but don't rely on them, since they can rely on their
internal terminology to a reasonable extent (but not for value sets like
procedure or diagnoses etc). In theory, we should do what fils guides
are doing, and the reason we have not is only practical, not
theoretical: the development of bio-medical ontologies is still young,
and was almost non-existent 18 years ago when we started on this.
The consequence has been that it is possible to construct archetypes
that say questionable or even wrong things with respect to ontologies of
those same things, say anatomical relationships. This rarely happens in
reality simply because archetypes are built by clinical professionals
and reviewed by many others, and mistakes tend to be avoided, or if
made, caught in review. But clearly it's not a completely reliable
strategy, and future versions of archetype tooling should force live
checking against suitable ontologies to detect errors. Unfortunately, we
still don't have such ontologies in anything like the necessary detail -
despite the existence of OGMS, and numerous specialist OBO ontologies.
SNOMED CT doesn't come close to what is needed here. We still lack a
comprehensive ontology covering all of general medicine.
Secondly, the 'utterances' represented by archetypes are not intended to
be directly linguistic expressions, but rather constitute an underlying
structural /reference/ 'terminology'. The fils guides on the other hand
express natural language utterances, i.e. they are like a structural
/interface/ terminology. With archetypes on the other hand, the names of
elements are used as a default to name fields etc in the UI, but may
always be overridden by some interface vocabulary, or more likely a
layer of language-level templates tied back to templates based on
archetypes. In openEHR we have no system for doing the latter at the
moment, although it is often mentioned as a nice idea...
- thomas
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