Fan Trap, Chasm Trap

building semantic layer
1

Hi to all, :slight_smile:

What’s Fan Trap and Chasm Trap? How i find the Fan Trap and Chasm Trap problem in Universe and how to solve that problem?

Any of your advice/help is greatly appreciated.

Regards,

Shankar

silv_shankar :india: (BOB member since 2006-04-03)

2

Did you even try and search the forum for an answer? https://bobj-board.org/t/15227/14

jobjoris :netherlands: (BOB member since 2004-06-30)

3

A fan trap is where, in a data model, you have a m:1:1:m set of relationships; that is a central entity/table has a 1-to-many relationship on each side of it. Because of this set up, it’s not possible in a relational databse to specifically relate an individual record in the entity/table on one side of the set of relationships with a record in the entity/table in the other side. (If you draw out a simple diagram with the 3 entity/tables, you’ll probably see this more clearly.) Hence it needs to be resolved by restructing the data model, if there is a need to generate reports based on these 3 entity/tables.

A chasm trap is a bit more difficult to explain without a diagram. A chasm trap is where you have a 1:m:1:m set of relationships between 3 entity/tables and the relationships are optional (ie there may, or may not be, a record on the ‘1’ side of the relationship for a given record on the ‘m’ side). In this case, if you are trying to link records from the entity/table on one side of the 3 with those on the other side they won’t all connect and any report you construct could give false info. Again, data model redesign is required.

Hope this helps. Any half-decent Database Design book will have these explained, and probably in a far clearer way than I’ve done here!

Cads :uk: (BOB member since 2006-04-10)

4

Moved from “Building Reports” --> BusinessObjects Classic to the “Semantic Layer” forum, which is where Designer topics get discussed.

I might also suggest that your read through the Designer FAQ (Frequently Asked Questions) in this forum.

Bobarella (BOB member since 2004-02-12)

5

my dear friend,
fan trap is there where cardinality is 1:m:m or vice versa & for chasm trap cardinality condition is m:1:m

Regards,
Vinesh

pvinesh :india: (BOB member since 2005-12-06)

6

From the Designer FAQ…

What is a fan trap…
What is a chasm trap…

Anita Craig :us: (BOB member since 2002-06-17)