Views vs Tables

[kado]

Hello Gurus,

In the past we've gravitated towards sourcing our FM models from Views that point directly to our reporting database tables (typically called the dimensional layer with star/snowflake models). The views have provided flexibility and simplicity when having to make changes to derived fields, calculated columns and/or new requirements. I am curious what others have experienced and if there seems to be a preference of sourcing your model directly from your reporting tables or putting views on top of these tables to source.

Thanks,
mcaton

[blom0344]

It need not be database views. AFAIK you can pretty much build them as SQL query subjects in the FM model. We call them 'Cognos views'.
For the query optimizer it should not matter.
The competition (Business Objects) calls these 'derived tables' and these also only exist in the metadatalayer.
Cognos tries to make a point with proper modelling generating optimized SQL. Unless you are using a very ideal starschema to work against I feel that database views or Cognos SQL query subjects are a great way to provide flexibility in the transformation layer.