When a resource is updated by an API, servers generally do what?

• A. Merge tags (existing + new)
• B. Replace profile tags (existing with new)
• C. Merge security labels (existing + new)
• D. Overwrite the resource entirely

Answer: (A)

When a FHIR resource is updated via an API, the system treats tagging as additive metadata. The server is expected to merge the incoming tags with the existing ones, so you preserve any prior governance or classification labels while adding new ones. This approach avoids unintentionally losing previously assigned tags and keeps the resource’s metadata consistent across updates.

Think of the Meta element, where tags are stored as a set of codes. Rather than replacing the entire tag list, the server adds the new tags to the existing collection and avoids duplicating entries. This is why merging tags (existing plus new) is the typical behavior.

While it might seem plausible to replace other metadata like profiles or security labels, the question focuses on how updates handle tags, and the standard behavior in practice is to merge tags to preserve prior context. Replacing the entire resource or replacing just the tag set would risk losing important governance information.