Which resource is a collection of error, warning, or information messages that result from a system action?

• A. OperationOutcome
• B. Parameters
• C. Linkage
• D. DocumentReference

Answer: (A)

OperationOutcome is the FHIR resource designed to carry problems that occur during processing of a request. It acts as a collection of issues, with each issue describing an error, warning, or informational message produced by the system action. Each issue can include severity (fatal, error, warning, information), a code, diagnostics, and location, allowing a single response to convey multiple problems or notes.

The other resources serve different purposes: Parameters is for passing operation inputs and outputs; Linkage is for matching records that refer to the same real-world entity; DocumentReference is for pointing to or describing documents. Therefore, OperationOutcome best represents a collection of messages resulting from a system action.