Convention needed: Negated concepts

[rtmill]

Community request:

Convention for representing data that indicates an affirmation of the absence of an event or finding.

"Proven not to have happened"

@cgreich I believe has thoughts on this

[golozara]

For metastasis and genomics data, we use "negative", "positive" and "equivocal" to populate value_as_concept_id: Positive – concept_id=9191 Negative – concept_id=9189 Equivocal – concept_id=4172976 (rarely)

I don't think there is anything else that require a negative concept.