BusinessObjects Board

Detect Contexts and Joins ...

building semantic layer
#1

Fellow BOB members,

I am curious what experiences people may have had with using the Detect Contexts and Detect Joins features and whether anyone deems them as reliable and as such uses in them in any of the Productised BO systems they develop and maintain. Does anyone actually use these features? I am one for detail, so I prefer manually setting Contexts and Joins myself, but just curious what some of you think of these features.

Thanks in advance.

bobbafett (BOB member since 2007-10-18)

#2

There is a sticky topic in semantic layer and also in Designer FAQ
Read me - contexts & Aliases’

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haider :es: (BOB member since 2005-07-18)

#3

I abuse the joins to detect the contexts. To put that more precisely, I set joins manually (mainly because I have a data schema and the join setting is then within my hands - BO’s join setting logic isn’t the best) and then any one-to-one joins I set as one-to-many joins in the way in which I want contexts detected. This gives the benefit of not missing any joins out of contexts.

#4

Thanks for this. However, it doesn’t quite meet my needs on this occasion.

Basically, I’m really curious to find out what experiences people have had with using the ‘Detect Contexts’ and ‘Detect Joins’ features when using BO Designer to design BO Universes and whether people are actually using and relying on these suggested joins and contexts provided/suggested by the ‘Detect Contexts’ and ‘Detect Joins’ features of BO Designer.

Thanks.

bobbafett (BOB member since 2007-10-18)

#5

Unless you’re universe is a perfect multi-star schema, I wouldn’t use it. It will take you longer to check that it did it right than it will to just do it yourself.

As mentioned, it works but only in a perfectly designed database where you have all the cardinalities set perfectly.

Steve Krandel :us: (BOB member since 2002-06-25)

#6

OK, to expand on what I said above.

Experience of detecting joins is ghastly. Try it yourself and see.
Save your universe, detect joins and then save it as something else.
Check your joins and see the differences.

Detect contexts works great if, as Steve said, you’ve got a nice set of fact tables and dimension tables that are all one-to-many joined. In that circumstance I would have no hesitation setting my joins manually and then hitting the Detect Contexts button and adding all suggested contexts. This has the big benefit of not missing any joins out of contexts,

The best thing that I can suggest is experiment with, say, 2 fact tables and 4 dimension tables. My suggested approach also works if you’re fast-tracking a universe build because you don’t have a complete set of warehouse data available or if you’re working offline at home over a weekend having simply dumped all tables into your universe canvas on a Friday afternoon and taken your laptop home. Detecting joins obviously won’t work remotely but detecting contexts will.