Hi There
Yes the attribute relationship is really very important especially when you are using user defined hierarchy. So what you need to do you should create Prod ID as key column and Prod Abbv as name column, Sub ID as key column and Sub Abbv as name column similarly Group ID as key column and Group Abbv as name column as and then create relationship between Prod ID > Sub ID > Group ID.
You do not need to create relationship between
Prod Abbv > Sub Abbv > Group Abbv as these are just mask to the relevant
Prod ID > Sub ID > Group ID.
Your end user will not see Prod ID > Sub ID > Group ID but can only see
Prod Abbv > Sub Abbv > Group Abbv.
If you still need to use Id for slice and dice you can create a new attribute from id columns and make them visible for end user
Hope this will help. If you need further clarification please let me know
Many thanks
Qazafi