Claim diagnosis (http://hl7.org/fhir/r4/claim-definitions.html#Claim.diagnosis) includes a sequence (A number to uniquely identify diagnosis entries) and a claim.diagnosis.type that seems to indicate how the diagnosis relates to the claim (admitting, discharge, etc.) - Also, claim.diagnosis.onAdmission (seeming to accommodate the US need for a PresentOnAdmissionIndicator).

Claim procedure has similar modeling with type (referring to primary and secondary that seem to indicate primary an secondary with respect to a series of procedures that are related, but not necessarily the "primary" procedure for an Encounter).

Encounter diagnosis (http://hl7.org/fhir/r4/encounter-definitions.html#Encounter.diagnosis) has a condition, use and rank (but not an onAdmission indicator the encounter.diagnosis.condition does reference a diagnosis or procedure but it is not intuitive to reference a procedure as a diagnosis or condition. Use is defined as "Role that this diagnosis has within the encounter (e.g. admission, billing, discharge …) DiagnosisRole (Preferred)" which is a different value set than the claim.diagnosis.type. and Rank is defined as "Ranking of the diagnosis (for each role type)" which seems almost the same as the claim.diagnosis.sequence.

FHIR should harmonize claim.diagnosis and encounter.diagnosis as well as claim.procedure and encounter.diagnosis.condition (that may accommodate procedure). FHIR should also clarify the meaning of a procedure.type in that the primary and secondary seem to be related to the same series, not necessarily the primary procedure for the Encounter. Also differentiate primary from principal.