Chasm and Fan traps (BusinessObjects Universe)

Relational databases can return incorrect results due to limitations in the way that joins are performed in relational databases. Unlike loops, which return fewer rows, the Chasm and the Fan traps are two common circumstances which return too many rows. You can use Designer to resolve both types of problems in your universe schema.

The Chasm trap occurs when two “many to one” joins converge on a single table. For example a customer can place many orders/and or place many loans.

The Fan trap occurs when a “one to many” join links a table which is in turn linked by another “one to many” join.

For example when you run a query that asks for the total orders by each order line, for a particular customer, an incorrect result is returned as you are performing an aggregate function on the table at the “one” end of the join, while still joining to the “many” end.