#238: Clarified how prefetch data is processed (and that the specification is not prescriptive about that).

Author: brynrhodes

docs/specification/1.0.md

@@ -226,6 +226,8 @@ An EHR MAY choose to honor some or all of the desired prefetch templates, and is
 
 The EHR SHALL deny access if the requested resource is outside the user's authorized scope.
 
+As part of preparing the request, an EHR processes each prefetch template it intends to satisfy by replacing the prefetch tokens in the prefetch template to construct a relative FHIR request URL. This specification is not prescriptive about how this request is actually processed. The relative URL may be appended to the base URL for the EHR's FHIR server and directly invoked, or the EHR may use internal infrastructure to satisfy the request in the same way that invoking against the FHIR server would.
+
 Regardless of how the EHR satisfies the prefetch templates (if at all), the prefetched data given to the CDS Service MUST be equivalent to the data the CDS Service would receive if it were making its own call to the EHR FHIR server using the parameterized prefetch template.
 
 > Note that this means that CDS services will receive only the information they have requested and are authorized to receive. Prefetch data for other services registered to the same hook MUST NOT be provided.