I’m still not sure what additional value we get from the identifier field for this use case!
For value field, why is valueString the only option? At least valueQuantity should be permitted so as to allow accurate representation of, for example, blood pressures, blood test results etc. This is important as it will be required for clinically safe interpretation of the value in comparison to the referenceRange is permitted; it uses numeric values. For a trivial example in javascript, ‘2.1mmol/L’ < 4.0 is false, we’ve just missed our hypoglycaemic patient.
Why is value required? If the observation is a composite, using components (say, blood pressure) then will the value still be required?