Under the Unit two redunant attributes SuperiorUnit and SubUnits are defined.
Only SuperiorUnit is needed since all Units that have the same SuperiorUnit defines the SubUnits list of the SuperiorUnit. I know that it is easy to have both but it can lead to inconsistencies.
Note that at the higest level the SuperiorUnit can be empty since there is no parent. That is not mentioned in the semantics.
Under the Unit two redunant attributes SuperiorUnit and SubUnits are defined. Only SuperiorUnit is needed since all Units that have the same SuperiorUnit defines the SubUnits list of the SuperiorUnit. I know that it is easy to have both but it can lead to inconsistencies. Note that at the higest level the SuperiorUnit can be empty since there is no parent. That is not mentioned in the semantics.