Author Topic: FM durable model  (Read 352 times)

Offline sdf

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FM durable model
« on: 29 Jan 2018 04:21:36 am »
Hi Gurus,

Jus want to scout info regarding Durable FM model/package.
What is the expected behavior of the reports using a durable model.
Also. is there a way to convert an existing model to be a durable model?

THanks!

Offline MFGF

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Re: FM durable model
« Reply #1 on: 29 Jan 2018 05:50:14 am »
Hi Gurus,

Jus want to scout info regarding Durable FM model/package.
What is the expected behavior of the reports using a durable model.
Also. is there a way to convert an existing model to be a durable model?

THanks!

Hi,

A durable model is all about the approach you take when designing the model. The idea is that it isolates the reports as much as possible from changes in the underlying data structures. For this to work, you need to use multiple layers in your model - a lowest-level data source view (with relationships defined and traps resolved), a Model view above that, comprising model query subjects fed from the data source query subjects, providing an abstraction layer and a place to add calculations, filters, intuitive names, intuitive groupings of data etc, and finally a Business View above that, comprising shortcuts to the model query subjects, grouped into different subject areas as a basis for your package creation.

The expected behaviour of reports from any model - durable or not - is that they deliver accurate, consistent results. The benefit of having them based on a durable model is that if (for example) the name of a table changes in the database, it can be amended in the data source view without affecting the names used in any reports - therefore meaning the reports do not break.

If you already have a model that is created without regard for durability, it will be a big job to amend it - not least because you will invariably need to fix every report based on your model once you start introducing friendly names and groupings of data. There is no "convert" option, other than to design how you want your model to be structured and make the relevant changes to it. As above, you would then need to fix all your reports...

Cheers!

MF.
Meep!

Offline dougp

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Re: FM durable model
« Reply #2 on: 29 Jan 2018 10:59:57 am »
I generally agree with MFGF when I consider the definition of durable.  However, IBM defines a durable model in a very specific way.

https://www.ibm.com/developerworks/data/library/cognos/modeling/design/page496.html
https://www.ibm.com/support/knowledgecenter/en/SSWGNW_10.1.0/com.ibm.swg.im.cognos.ug_fm.10.1.0.doc/ug_fm_id11629DurModel.html

Basically, it means that if you change the names of namespaces, query subjects, and/or query items in the active language, reports do not break because they use the design language.  The key instruction in IBM's documentation is this:

Quote
The design language name of all namespaces, query subjects, and query items that are published in a package must never change after the package is initially published.


Of course, what MFGF says is also a great idea.  Manage your model well so that reports don't break.  Or don't.  For example, if a column is being deleted from your source data, consider how the users want their old reports to behave.  Maybe breaking is good so they'll fix the reports.  Maybe they want that column blank.  Every project is different.

« Last Edit: 29 Jan 2018 12:04:14 pm by dougp »

Offline sdf

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Re: FM durable model
« Reply #3 on: 29 Jan 2018 07:00:19 pm »
alright! thanks for your replies @MFGF and @dougp :)

 


       
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