Clarify the use of basedOn

[bdc-ehealth]

comments by @costateixeira
basedOn should only be used (see description in standard) if the ServiceRequest is a request to (partially) fulfill another request (in our case a proposal).

If we want to link a prolongation (order/proposal) to a previous prescription we need an extra extension

[Mcobbaert]

Why do we need an extra extension ? Can you please explain ?

[bdc-ehealth]

@Mcobbaert @annenerenhausen It is about semantic interoperability. ServiceRequest.basedOn (http://hl7.org/fhir/R4/servicerequest-definitions.html#ServiceRequest.basedOn) refers to another item that is being fulfilled by this one. It can thus refer to a proposal, careplan, ... . A prolongation of a request does not fulfill the other request, it is an addition to the other request. That is semantically different. Therefore we propose a new extension.

[bdc-ehealth]

WG: "replaces" will be used for prolongations -> see the detailed comments in the standard. "basedOn" will be used in case of a proposal, reference to a Careplan, or any other prior resource that causes this request. "duplicate": is still open.

[bdc-ehealth]

WG: in case of a "duplicate", we don't need the link between the new ServiceRequest and the ServiceRequest it is based on. So we can drop the third option.