Why this measurement definition exists: the specific ambiguity or unit trap it prevents. Required on every definition, because a definition that cannot name the failure it prevents is a guess, and the failures this guards against (affine unit conversions, off-by-one ordinal scales) produce numbers that render and validate while being wrong. Carried as an extension because R4's ObservationDefinition has no narrative element; it retires into description on a move to R5.
Elements / Details
Every element this profile touches, with its full definition. Element names in the tables link here.
Why this measurement definition exists: the specific ambiguity or unit trap it prevents. Required on every definition, because a definition that cannot name the failure it prevents is a guess, and the failures this guards against (affine unit conversions, off-by-one ordinal scales) produce numbers that render and validate while being wrong. Carried as an extension because R4's ObservationDefinition has no narrative element; it retires into description on a move to R5.
May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.
Comments
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 level of simplicity for everyone.
Source of the definition for the extension code - a logical name or a URL.
Comments
The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Names the concrete failure: which two conventions are confusable, and what goes wrong when they are confused. Prose, addressed to whoever is deciding whether to change or remove this definition.