Dear All,
What is the use of cardinality in universe.
Rakesh_K 
(BOB member since 2007-12-11)
It looks pretty
and it’s used by the ‘detect’ functions in designer
detect loops, detect contexts, detect aliases all rely on the cardinality of joins being known in order for it to work out how best to resolve loops and apply contexts/aliases.
It has no direct impact on the generated SQL. In other words if you join one fact table to one dimension table and then run a query involving objects from the both tables, the SQL is the same whether cardinalities are applied to the join or not.
My rule of thumb is that visually it can be helpful to show cardinalities in the universe, but always apply the cardinalities manually. Never use detect cardinalities, detect alises/loops/contexts. If you are designing a universe it is implied that you understand your data structures and therefore understand the cardinalities of the joins and can work out for yourself where aliases and or contexts should be used
Good luck
richmona 
(BOB member since 2003-04-15)
This topic also helps. I would suggest to go through designer guides from here.
Jansi (BOB member since 2008-05-12)