Canonical constraints

Can canonical references outside of a resource’s url field, for example Questionnaire.derivedFrom, be relative? Do they also need to be FHIR RESTful compliant?

In our use case we want to link to a FHIR resource relative to our server, but not sure if it needs to be in the //id form or if it can be in an arbitrary path

Edit: my understanding from the docs is that it could be relative, and references only MAY be FHIR API compliant. Just not 100% confident on my understanding of the docs

Canonical references must be absolute or be to a contained resource. However, there’s no requirement that they resolve or comply with FHIR’s RESTful naming conventions. (Though it’s nice if they do).

The purpose of a canonical URL is to be a value that can be consistent regardless of what server or registry the artifact is copied from - given that there will typically be copies of them on a wide variety of servers.

Makes sense, thanks Lloyd