There's a code for primary author, co-author and author, but no specialization relationship between them. We have Event Witness and Witness.

Amender makes no sense. If the activity that the provenance is recording is "amending", then the amender is the author. If the activity being recorded isn't amending, then amender can't be relevant.

Affiliate, agent, claimant, covered party, dependent, employee, next of kin, health care provider, etc. all have no relevance here. They don't describe what action the person is involved with with respect to the provenance action. These concepts do not belong in this terminology which is about "role in the provenance", not "capacity of the individual". (In RIM terms, this is about participation, not role - it's linking an individual to an act, not to another individual.)

Same is true of grantee, grantor, durable power of attorney, etc.