Canonical url

FHIR defines the use for "canonical urls" for some different resource types like StructureDefinitons (=profiles and extensions) - or also instances of Questionaire, ActivityDefinition. Canonical url has two impacts:

• it is serving as a reference
• it should be globally unique

Example

medico's patient profile has the following canonical url:

https://medico-emr.net/medico/r4/sd/Patient_Patient_1

In fact - at the time of this writing - you can't download the profile with this url.

So how is it useful then? The answer lies in the references:

• All other medico FHIR resources - e.g. Patient- or Encounter resources - refer to this profile when passing back their data.

Those canonical urls are used on two different levels:

• product-level

  i.e. an instance looks the same to all medico-tenant example - how a patient is defined: https://medico-emr.net/medico/r4/sd/Patient_Patient_1

• tenant-level

  i.e. an instance looks different to all tenants example: how an ActivityDefinition for a careplan is identified: https://medico-emr.net/medico//[id value] note here the place-holder that makes this canonical url unique