Hi Naomi,
"Do you derive any master data from BW for Entity and Title? If yes, does one of entity or titles have compounded attributes e.g. Entity is the compounded of title? " - NO!
"Another question is, may I know whether you use concatenation, and in what scenario, you need concatenation?"
Concatenation is used if you want to avoid additional dimension creation and you don't need to have totals for both dimensions (like total per CC for all CA and total for CA for all CC).
Vadim