From clause
Functional
The `from clause takes all resources from a data-source as input. It produces a subset of those resources by filtering them on resource type. The functional shape of this clause is:
list-of-node -> from -> list-of-node
Syntax
from-clause: 'from' resourcetype
resourcetype: known-fhir-resource | 'Resource'
Optional
A from clause is optional. If a data source is accessed without a from
clause, the next clause in the pipeline,
will take the full data set as input.
using 'hl7.fhir.r4.core'