A resource id for one of proposed Slots returned by a prior $find operation (e.g., Resource/1234). References can be to an absolute URL, but servers only perform this operation on their own slots.

When slot-identifiers are provided, the server is expected to perform an internal lookup to identify the corresponding slot instance. The server SHALL reject the request if the provided identifiers do not resolve to a single slot instance.

To create a hold on the slot this parameter needs to have the value busy-tentative or free to release it.

The response will be a Parameters resource consisting of the requested held Slot resource, an OperationOutcome with errors, warnings or information as a result of processing the operation and in upon successful creation of a hold a dateTime held-until, which signals when the hold is automatically released. The Appointment resource will have an updated status of "busy-tentative" if the hold is approved or "busy-unavailable" if the hold is rejected.