The reviewer recommends using components to represent the circumstances associated with Observations. This is interesting recommendation considering that: 1) The FHIR specification (see http://hl7.org/fhir/R4/observation.html#gr-comp ) indicates components are for "supporting results" (note results , not preconditions or circumstances). The specification does not suggest Observation.component should be used for circumstances or preconditions. 2) The practice of representing circumstances and reconditions by extensions is reinforced by the presence of standard extensions designed specifically for capturing circumstances and/or preconditions of measurement: (a) A standard extension for bodyPosition of an observation: http://www.hl7.org/fhir/extension-observation-bodyposition.html (b) A standard extension for general preconditions: http://hl7.org/fhir/StructureDefinition/observation-precondition 3) It is suggested that blood pressure cuff should be captured in Observation.component, but the cuff is the Observation.device, and the size of the cuff is clearly a part of the description of that device. (The same is true if DeviceMetric is used instead of Device). 4) We believe this recommendation displays a stigma against extensions. To quote the specification, "Unlike many other specifications, there can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core simplicity for everyone." Although we find the suggestion to use components for circumstances and preconditions non-persuasive, we will nonetheless reconsider each observation extension to determine: (1) if can be considered a result, and hence suitable for an observation component, (2) whether we have maximized the use of standard extensions. Proposed resolution: Persuasive with mod