Dimensional Data Structure and Unit Data Structure

[JALinnerud]

The current definitions are
"structure of an organised collection of a dimensional Data Set"
"structure of an organised collection of unit Data Set "
Given that the definition of Data Set is "organised collection of data" there seems to be some redundancy in these GSIM v2.0 definitions.
Action: Replace the definitions with "describes the structure of a dimensional Data Set" and "describes the structure of a unit Data Set"