Shashikumar

• Jun 21st, 2007

 

EDW & DW are one & the same.

If scope of data warehouse is enterprise wide it is called Enterprise data warehouse.
If the scope of data warehouse is limited to department it is called Data mart.


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jryan999

 Profile Answers by jryan999 Questions by jryan999

• Sep 1st, 2008

 

I quite agree with the Enterprise Vs Departmental warehouse.  Some background through.

The two primary warehouse architectures are proposed by Kimball and Inmon. 

Inmon used to recommend a single "Enterprise" warehouse, probably held in relational form (ie. 3rd Normal Form), which would be accessed directly, or more likely, used to feed "Data Marts" - smaller dimensional "warehouses" for departmental use.

Kimball suggests this "big bang"approach takes too long to deliver, probably delivers the wrong thing (the business has moved on by the time you deliver it), and recommends instead takling the problem as smaller, more managable steps.

He recommends taking a single business process (eg. Inventory management) then producing one or more Dimensional models to produce Fact/Dimension tables to support the problem. 

Once you've done one, you move onto the next.

The argument against the Inmon "Enterprise" approach is it's too large and too expensive.  The argument against the Kimball approach is it risks producing inconsistent results across departmental systems which are not integrated.

Kimball answers this, with the "Data Warehouse Bus" architecture whereby Dimension values are maintained consistently across the departmental data marts.  For example a "Product Type" means the same thing (same values) in Sales, Inventory and Marketing.  This eliminates the inconsistency.

Personally I follow the Kimball approach (it's now very common as a design technique as Dimension --> Fact Dimensional design produces fast, flexible systems. 

Don't forget though, the "Incremental" approach can be hosted centrally (with huge advantages for security, control and operations), built incrementally and eventually become the "Enterprise" solution.

Hope this helps de-mystify  what can see a load of marketing tosh.