POSSIBLY_EQUIVALENT_TO - Editorial Guide

Current usage:

The POSSIBLY_EQUIVALENT_TO association is used where an inactive concept was previously the conflation or disjunction of two or more distinct possible meanings, at least one of which is also now represented as a current SNOMED concept.

Ambiguity may arise due to an inherently ambiguous FSN or from the presence of synonyms which are deemed to be either partial or non-synonymous with the meaning of the FSN.

While the expectation is that there will be two or more targets, each representing an element of the disjunction or conflation, there are some instances where only a single target is required. These currently include FSNs in which there is only one element considered to be clinically useful and the other is where the FSN represents a classification concept such as 'other' or 'NOS'.

Proposed changes:

The POSSIBLY_EQUIVALENT_TO association is to be used where an inactive concept was previously the conflation or disjunction of two or more distinct concepts ALL of which are clinically meaningful. The sum of the targets should be semantically equivalent to the semantic meaning of the inactivated concept and where one or more concepts required to achieve semantic equivalence does not currently exist within SNOMED CT they should be created. Therefore, the steps proposed are:

Resolve non-synonymous synonyms by inactivation of the descriptions and re-assign to either existing concepts which are semantically equivalent or by creating new concepts
Establish that the ambiguous FSN requires 2 or more clinically useful concepts are required to maintain semantic equivalence
If after due diligence only one target is considered to be clinically useful then the association type should be 'REPLACED_BY'

Combinatorial Logic:

Whenever an already stated POSSIBLY_EQUIVALENT_TO target itself also becomes inactive - whether at the same release or later - the combinatorial logic of associations should be:

(A) POSSIBLY_EQUIVALENT_TO (B OR C) and (B) SAME_AS (D) implies A POSSIBLY_EQUIVALENT_TO (C OR D)

(A) POSSIBLY_EQUIVALENT_TO (B OR C) and (B) REPLACED_BY (D) implies A POSSIBLY_EQUIVALENT_TO (C OR D)

(A^IntEd) POSSIBLY_EQUIVALENT_TO (B^IntEd OR C^IntEd) and (B^IntEd) MOVED_TO (D^NRC) implies (A^IntEd) POSSIBLY_EQUIVALENT_TO (C^IntEd)

A POSSIBLY_EQUIVALENT_TO (B OR C) and (D) MOVED_FROM (B) implies A POSSIBLY_EQUIVALENT_TO (C OR D)

(A) POSSIBLY_EQUIVALENT_TO (B OR C) and (B) POSSIBLY_EQUIVALENT_TO (D OR E) implies A POSSIBLY_EQUIVALENT_TO (C OR D OR E)

(A) POSSIBLY_EQUIVALENT_TO (B OR C) and (B) WAS_A (D AND E) implies ((A) POSSIBLY_EQUIVALENT_TO (C) OR (A) WAS_A (D AND E))