Before deciding to build a data warehouse for your organization, you need to ask the following basic and fundamental questions and address the relevant issues:
- Top-down or bottom-up approach?
- Enterprise-wide or departmental?
- Which first—data warehouse or data mart?
- Build pilot or go with a full-fledged implementation?
- Dependent or independent data marts?
Top-Down Approach
The advantages of this approach are:
- A truly corporate effort, an enterprise view of data
- Inherently architected—not a union of disparate data marts
- Single, central storage of data about the content
- Centralized rules and control
- May see quick results if implemented with iterations
The disadvantages are:
- Takes longer to build even with an iterative method
- High exposure/risk to failure
- Needs high level of cross-functional skills
- High outlay without proof of concept
Bottom-Up Approach
The advantages of this approach are:
- Faster and easier implementation of manageable pieces
- Favorable return on investment and proof of concept
- Less risk of failure
- Inherently incremental; can schedule important data marts first
- Allows project team to learn and grow
The disadvantages are:
- Each data mart has its own narrow view of data
- Permeates redundant data in every data mart
- Perpetuates inconsistent and irreconcilable data
- Proliferates unmanageable interfaces