When an IG is calling on a FHIR core extension, and that core extension has a defined search parameter... (e.g. mothersMaidenName).

It is clear how to call for the extension in a StructureDefinition.

It is not clear what all is needed in a CapabilityStatement (requirements) to call for the search parameter for that extension.

is it sufficient to just address it the same way as core defined parameters?

or one must find the canonical URI of the SearchParameter? For example for mothersMaidenName
 http://hl7.org/fhir/SearchParameter/patient-extensions-Patient-mothersMaidenName
if the canonical URI is needed, then we really MUST make these more clear. I only found this by searching deeply the FHIR core build output. I can't find mention of this anywhere in the narrative.

Vassil Peytchev: It is needed, and I learned to find the canonical in the core package (since it is a tar.gz package, you can just look inside with you favorite compression app).

John Moehrke: yup, geeks can find... but not the kind of author we want to attract to IG publication.

https://chat.fhir.org/#narrow/stream/179252-IG-creation/topic/CapabilityStatement.20and.20core.20extension.20search