4.1.1. Improve description of  excludeNested Replace existing text with the following: Controls whether or not the value set expansion may nest codes or not (i.e. ValueSet.expansion.contains.contains). If excludeNested is set to  true , the expansion MUST be flat (no nesting). If excludeNested is set to  false  (default),  however, nesting is possible but not required. https://github.com/gabriel0316/FHIR-30700#412-improve-description-of-excludenotforui 4.1.2. Improve description of  excludeNotForUI Replace existing text with the following: {{}} Controls whether or not the value set expansion might include codes from the CodeSystem with a  notSelectable  property set to  true  as specified in  http://www.hl7.org/fhir/codesystem.html#status  and in  https://hl7.org/fhir/R4/codesystem-concept-properties.html nested  contains  with no code (see  http://www.hl7.org/fhir/valueset-definitions.html#ValueSet.expansion.contains.code ) nested  contains  in the ValueSet with  abstract = true  (see  http://www.hl7.org/fhir/valueset-definitions.html#ValueSet.expansion.contains.abstract ) One purpose of such concepts is helping a user navigate through the list efficiently. If excludeNotForUI is set to  true , the concepts as described above will be excluded from the expansion. If excludeNotForUI is set to  false (default), all concepts as described above may be part of the expansion. In the FHIR Specification itself, the value set expansions are generated with  excludeNotForUI = false , and the expansions used when generating schema / code etc, or performing validation, are all  excludeNotForUI = true .