Primitive extensions #5
Description
Problem
In FHIR you could extend primitive types with additional attributes.
This encoded in JSON with "_" prefix and has similar to variable type elements problems
with collections, schema, databases etc:
{
value: 42'
_value { extension: [....]}
}
Solution 1
We could apply the json-ld approach and encode primitives with objects:
{
value: {
@type: "Number",
number: 42,
extension: [...]
}
}
Additionally, we fix weak typed JSON by embedding type labels into object
We pay by deeper paths and some size of Resource (because of additional $type labels):
obj.value vs obj.value.number
{
resourceType: "Patient",
id: "example",
identifier: [ ... ],
active: {
@type: "boolean"
boolean: true
},
gender: {
@type: "code"
code: "male"
},
birthDate: {
@type: "date",
date: "1974-12-25",
extension": [
{
"url": "http://hl7.org/fhir/StructureDefinition/patient-birthTime",
"valueDateTime": "1974-12-25T14:35:45-05:00"
}
]
}
deceased: {
@type: 'boolean',
boolean: false
},
managingOrganization: {
"reference": "Organization/1"
}
}
But we simplify typed parsing of JSON because of type information is in the document
and does not require lookup in meta-data.
We also allow collections of extended primitives.
We could go farther and add $type annotation attribute to other elements
(i.e. complex elements or datatypes):
managingOrganization: {
"reference": "Organization/1"
}
managingOrganization: {
@type: "Reference",
"reference": "Organization/1"
}