- , where "ambiguous" carries the strict interpretation of: has more than one distinct and individually unambiguous interpretation. The most obvious form of ambiguous FSN is one that contains an explicit disjunction, for example 178841003 Complex reconstruction operations on hand and foot, where 'and' almost certainly really means 'or'. The ambiguous nature of this code is perhaps most easily revealed if we consider the universe of all patients with an EPR entry of 178841003, and then ask which should be returned in response to a query for all patients who have had a <<112746006 Operative procedure on hand ? Of course, we don't know; some had a foot operation. This thought experiment is "diagnostic" of an ambiguous term.
Note that this therefore precludes using Ambiguous in cases where nobody knows what the FSN means at all, and so no active concept(s) can be identified that precisely correspond to even one of its distinct meanings. For example, 194964003 Milk spots of pericardium is clearly some kind of pericardial disorder or sign, but exactly what has long been lost in the mists of medical time. However, as far as we know, this term only ever had one clear and unambiguous meaning - we just don't know what it was. The reason for inactivation of such concepts should be stated to be Outdated, or possibly "reason not stated". But not Ambiguous.
- A special case of a concept with more than one possible unambiguous interpretation concerns where there is a mismatch between an apparently unambiguous FSN, and the modelling assigned to the same concept. In this scenario, the set of ancestors and descendants (if any) computed by a reasoner for the concept will be inconsistent with what is implied by the FSN. Mismatch patterns will therefore include:
- Modelling is for a completely different category to the FSN meaning; this obviously includes where a concept needs to be moved to a different top-level hierarchy (except when between permitted pairs of top-level hierarchy)
- Modelling is semantically more precise than the FSN meaning
- The FSN meaning is semantically more specific than the
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