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Fan Trap, Chasm Trap


 
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silv_shankar
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Joined: 03 Apr 2006

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PostPosted: Mon Apr 10, 2006 12:49 am 
Post subject: Fan Trap, Chasm Trap

Hi to all, icon_smile.gif

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
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jobjoris
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Joined: 30 Jun 2004

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PostPosted: Mon Apr 10, 2006 12:59 am 
Post subject: Re: Fan Trap, Chasm Trap

Did you even try and search the forum for an answer? http://www.forumtopics.com/busobj/viewtopic.php?p=145720#145720
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Cads
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Joined: 10 Apr 2006

Posts: 36
Location: UK


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PostPosted: Mon Apr 10, 2006 7:12 am 
Post subject: Re: Fan Trap, Chasm Trap

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!
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Bobarella
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Joined: 11 Feb 2004

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PostPosted: Fri Apr 14, 2006 7:21 pm 
Post subject: Re: Fan Trap, Chasm Trap

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.

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pvinesh
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Joined: 06 Dec 2005

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Location: London, UK


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PostPosted: Sat Apr 15, 2006 8:58 am 
Post subject: Re: Fan Trap, Chasm Trap

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


Last edited by pvinesh on Mon Apr 17, 2006 11:55 pm, edited 1 time in total
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Anita Craig
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Joined: 17 Jun 2002

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Location: Palo Alto, California, U.S.A.


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PostPosted: Mon Apr 17, 2006 7:08 pm 
Post subject: Re: Fan Trap, Chasm Trap

From the Designer FAQ....

What is a fan trap...
What is a chasm trap...

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