In the current QDM, a procedure can be flagged as the principal procedure via the ordinality attribute. Unfortunately, there is not a way to indicate the encounter it is principal for except through timing (which is not as accurate as one would hope).

FHIR's Procedure contains an encounter attribute, although it is unclear how the notion of principal would be represented. Similarly, C-CDA R2's Procedure Activity Procedure has an entry relationship to an Encounter, but it is unclear how the notion of principal would be represented.

If possible, the solution should be consistent with the approach agreed upon for representing principal diagnoses (QDM-106). This would likely mean adding a principal procedure attribute to Encounter, Performed (and possibly a procedure attribute for capturing non-principal procedures, if necessary).