On 01/04/2018 13:16, GF wrote:
Pre-coordinated SNOMED codes are like classifications, in that they
are used at the user level, the User Interface,
The Ontology behind SNOMED allows the pre-ordinated codes to be
decomposed in its constituents.
These decomposed primitive codes can be used in structures like
archetypes at the proper places.
In this way the pre-coorodinated SNOMED codes are iso-semantic.
But we keep the semantic differences codes expressed using the SNOMED
ontology and the Archetype and its codes.
Ontologies have the Open World Assumption. A pre-corodinated code
like: No-Cancer means never there was, is or will be cancer.
Ontologies describe reality.
In archetypes that use the Closed World Assumption Diagnosis=cancer,
PresenceModifier=No means No Cancer found but perhaps they are. It
just was not found. Presence of absence in a database are described.
I'm unclear why you call this a use of the closed world assumption: the
entire openEHR framework is for building HISs that enable reporting of
reality as it is known to those working in it. So if they put 'No
cancer' that just means that the current clinical thinking for some
patient, /with respect to some investigation/, is that the original
presenting problem is not cancer.
That never means that the patient doesn't have cancer in their body
somewhere, it just means that the currently investigated signs and
symptoms don't relate to cancer, according to the the investigation
carried out. Even that can be overturned later. But everyone assumes
this - the EHR is always understood as an 'open world' system, where
absence of X doesn't mean negation of X, it just means that no-one has
investigated X.
- thomas
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