The National Directory InsurancePlan should be able to be used as a basis for directories in general (including directories acting as sources to the NDH). These source directories may be the organizations that own and administer all of the InsurancePlans in the directory, thus requiring ownedBy and administeredBy would represent an extra unnecessary data requirement. This is notable for things like Formulary where the Organization resource is not otherwise used.

Considering changing the cardinality of InsurancePlan.ownedby and InsurancePlan.administreredBy from 1..1 to 0..1