To understand an extension’s structure and constraints, which artifact should you consult?

To understand an extension’s structure and constraints, which artifact should you consult?

• A. ValueSet
• B. CodeSystem
• C. StructureDefinition
• D. CapabilityStatement

Answer: (C)

Understanding an extension’s structure and constraints comes from its StructureDefinition. This resource explicitly defines what the extension contains—its elements, data types, cardinalities, and any invariants that constrain usage. It also captures how the extension is identified (its URL) and how it is wired into resources (the path structure, differential and snapshot views). In short, the StructureDefinition is the definitive description of an extension’s shape and rules. ValueSet and CodeSystem relate to allowed codes and vocabularies, not the data structure of the extension, while CapabilityStatement describes what a system can do, not how a particular extension is structured.

Understanding an extension’s structure and constraints comes from its StructureDefinition. This resource explicitly defines what the extension contains—its elements, data types, cardinalities, and any invariants that constrain usage. It also captures how the extension is identified (its URL) and how it is wired into resources (the path structure, differential and snapshot views). In short, the StructureDefinition is the definitive description of an extension’s shape and rules. ValueSet and CodeSystem relate to allowed codes and vocabularies, not the data structure of the extension, while CapabilityStatement describes what a system can do, not how a particular extension is structured.