Currently in GSIM it seems you can only build 'flat' Category Sets and Code Lists - the only time a hierarchy is introduced is through the inclusion of Level in a Classification Item for Classification Schemes.

Some thoughts for discussion:

1. Should it be possible to create a Hierarchical Code List (ie, a code list with a hierarchy that is not a classification scheme), or a Category Set (a hierarchical set of Categories that have not been enumerated by Codes)?
2. Are the current definitions of Category Set and Code List broad enough to allow for the possibility of a hierarchical set?
3. Should Category Set and Code List also include a relationship with Level? (Allowing for the building of hierarchical set)