The FHIR specification expects requirements not part of the spec be implemented as what?

• A. Resource Extensions
• B. Profile Extensions
• C. Security Extensions
• D. User Extensions

Answer: (A)

When the base FHIR resources don’t define a needed data element, you add it as an extension on the resource. This lets you capture extra information without altering the core definitions, preserving interoperability while still meeting specific needs. An extension is identified by a URL and can carry simple values or nested structures, and it can be attached at the resource level or to a specific element. Profiles constrain or specialize resources and may require certain extensions, but the mechanism for adding new data remains extensions, not a separate “Profile Extension.” Other terms like security or user extensions don’t describe the standard method for introducing new data elements in FHIR.