FhirQuery

Research into a possible language for querying FHIR servers

Idea

Combine the strenght of existing languages to fill the gap of missing features, while trying not to reinvent the wheel. This idea serves to provide an alternative to GraphQL which is another good candidate to solve this problem.

Proposal

• Stay as close as possible to existing standard SQL.
• Use Json to create tree structures (DocumentDB language is a nice example)
• Use FhirPath for projection (select)
• Use existing FHIR search parameters for filtering (where)

Some examples

SQL Compatible

In terms of input format, this query still adheres to regular SQL

select name, birthDate from Patient where id = 4

Usage of FhirPath for projection

Fhir path statements return either a scalar or a collection of substructures of a resource. They can be used to build custom XML and JSON structures, but do not necessarily flatten the output hierarchy.

select 
    name.family, 
    name.given[0]
from
    Patient

Using FHIR Search parameters

FHIR search parameters themselves flatten the hierarchy of their corresponding resource, and are a natural fit for filtering.

select * from Patient where email = 'patientzero@test.com'