Single Resource

[ErwanBrunelliere]

Is there any reason of why the Resource element of the ViewDefinition is a single Resource and cannot be multiple ?
Like in SearchParameters, multiple resource FhirPath expressions will be possible 'Patient.name.given | Practitioner.name.given'

Thanks !

[bashir2]

I think one design goal for ViewDefinition was to act on a single resource only. Crossing resource boundaries, whether of the same type or different types is a non-goal and has been clarified recently in View Definition non-goals. Those kinds of joins/aggregations are left do downstream tools (e.g., databases) and the scope of ViewDefinition is limited to be an instrument for "flattening" FHIR structures. A side effect of this limit is that applying a ViewDefinition on a large FHIR store, can be horizontally scaled very well as each FHIR resource can be processed completely independent of other resources.