It looks like you have another big table in the data model that also has both BUs and Segments. So the synthetic key is expected to join the combinations from both.
The other table is a fact table that reports things like Sales etc.. it sounds like you are getting Sales reported for a combination of BU and Segment and need to analyze that vs. a target.
Knowing that i think a better data model would be to load BUs and their targets as one table, Segments and their targets as another table and load your main fact table 'as is'. Since BU and Segment are in the main fact table already you can create a cycle off those and still reference BU and Segment targets seperately.
at this point i'm completely open to having a skpe discssion to resolve this if you need...
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