The Cross-Version Extensions for FHIR (XVer) project provides a set of packages that define extensions, profiles, and value sets for cross-version compatibility in FHIR. These packages are designed to support the validation and interoperability of FHIR resources across different versions.
About This Guide
Cross-version extension content is generated via a combination of automatic differential detection and manual editing.
For details or questions, please reach out on Zulip or
to the FHIR Infrastructure WorkGroup.
Goals
Ability to use elements from another version of FHIR
Encode information added in a newer version of FHIR
Community identified additional data that is needed
Need to provide a consistent way of representing it in an earlier version of FHIR
Encode information removed in a newer version of FHIR
Community decided data was no longer necessary
Need to provide a consistent way of representing it in a later version of FHIR
Version migration requires interoperability between versions and cannot break old expectations
Scenarios where data needs to round-trip conversion between different versions
Known Limitations
Not 100% coverage of all elements in all versions
Resource type elements are excluded (e.g., R5:Bundle.issues)
Mappings are generally between adjacent versions, so “back-and-forth” conversions may be needlessly verbose
Large / infinite value sets (e.g., UCUM, LOINC, MIME) are excluded and assumed ‘equivalent’ across versions
Intellectual Property Statements
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