Comments
Cancellation, reversal or nullification depend on the current state of the Claim. Recommend operations defined for each of these along with processing rules given the state of the claim (e.g., an attempt to execute a reversal action on a cancelled claim ought to return a 409-Precondition failed response).

Grahame's Comments
I'm inclined to agree. Generally, the design of these resources is not typical of other FHIR usage, and that will require considerable inspection and consideration