Comment:

A resource asserting the existence of a risk and a resource asserting the absence of a risk should be clearly and easily differentiable. Ideally, this would mean an explicit assertion of presence or absence (e.g., as demonstrated in the substanceExposureRisk extension, though specified values would be useful). Wrapping negation inside of the code seems to violate a rule proposed for "modifier extensions" about modifiers inside date types. However, if there were a way to clearly and consistently distinguish these values (e.g., a requirement that such codes be fully defined, so that negation could be computably identified) and clear guidance on how to do this, that would be a positive move.

Summary:

Need to explicitly assert presence vs. absence of a risk