Data Warehouse Modeling

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Data Warehouse Modeling

Post  YoungBuddy on Wed Jul 14, 2010 5:22 am

Hello there,
Considering the case that i am assigned to work on, which is to decide on the most appropriate schema to be chosen for the Data Warehouse / Business intelligenece Project.
First of all, i would like to know the available options for me, (taken into consideration that the vendor proposed the Bus Matrix s a suitable schema to be implemented)
We are following the parellel approach in implementing the data warehouse (starting with data marts, while looking at the big picture so that outcomes are immediate and tangible on the short run, untill completing the entire data warehouse)

Unfortunately, I was not able to find a sufficient source including all schemas with the advantages and disadvantages of each. In addition to Bus matrix, snow flake and star schema .. what are the other options available ?
Please list the advantages and disadvantages of each of the mentioned shemas, and the proposed ones.
Thanks in Advance.

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Re: Data Warehouse Modeling

Post  ngalemmo on Wed Jul 14, 2010 3:34 pm

A Bus Matrix is not a data model, but rather a blueprint of the relationship between subject areas and dimensions to highlight integration points and help identify critical dimensions for the data warehouse.

The Bus Matix and Star Schema are design components relating to the development of a data warehouse using dimensional design techniques.

Alternatives involve implementing a data warehouse using some other architecture. The most well know alternative is Inmon's approach to build a data warehouse using standard ER modeling and publishing data marts from it. Those who implement DW's using such alternate approaches often lead a life forever burdened by the misery and harm they caused the business, dulled by the absence of true enlightenment, and punctuated by 2 am calls from operations because a data mart didn't load... (just kidding)
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Re: Data Warehouse Modeling

Post  YoungBuddy on Thu Jul 15, 2010 2:44 am

Thanks for your considerable response. I just understood the aspect of the bus matrix as a blue print to help me find the dimensions.
I know that generally there are two approaches in building the data warehouse, either the Inomn's approach (DW > data marts ) , and the parellel approach in which we start building several data marts with the aim to integrate them all in one single data warehouse on the long run.
My question is, What are the available data model design such as ( Star schema and snow flake ) ? Are there any other schema used in modeling the data ?
One last question please ... what are the factors considered in choosing a star schema rather than a snow flake ? .... since we have already adopted the parellel approach.
Thanks in Advance.

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Re: Data Warehouse Modeling

Post  BoxesAndLines on Thu Jul 15, 2010 8:50 am

YoungBuddy wrote:...My question is, What are the available data model design such as ( Star schema and snow flake ) ? Are there any other schema used in modeling the data ?
One last question please ... what are the factors considered in choosing a star schema rather than a snow flake ? .... since we have already adopted the parellel approach.
Thanks in Advance.

Yes, you can build a normalized data model for your data warehouse. I wouldn't classify star schema and snowflake as as different types of data models. Snowflake and Star schema are both dimensional models. I don't snowflake any dimensions unless there is database performance justification.
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Re: Data Warehouse Modeling

Post  ngalemmo on Thu Jul 15, 2010 12:55 pm

Kimball has written a few articles citing specific situations where a snowflake is acceptable. Off hand, I don't remember specific examples. If you search his articles (look for "snowflake") you should be able to find them.
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