From https://jira.hl7.org/browse/FHIR-35172

There doesn't appear to be any discussion of how the fhirVersion element of IGs, StructureDefinition, and requirement type CapabilityStatement fhirVersions should be used. (Or how the resource itself can be of a different version than the fhirVersion it specifies.) http://build.fhir.org/versioning is about identifying (or specifying) system or resource FHIR version; http://build.fhir.org/versions.html is primarily about managing spec versions. (E.g., there should be a discussion of what system or resource FHIR versions a IG, SD, or requirement-type CapabilityStatement with a given fhirVersion is compatible with. Is a 4.1.0 SD compatible with a 4.0.1, 4.1.1, or 4.6.0 system?) This discussion should be on a common page (to prevent different rules for different resources), but linked from each of the above resources.