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Introduce a phased approach:

Discovery

Requirements
Data quality

Architecture

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Rollout

Is this a replacement for all other BI methodologies? No

When to use this methodology

Spot analysis

Overview of the benefits of an agile approach and how it succeeds over the traditional approach (particularly when coupled with open source).
Include: early feedback, lower risk, better ROI estimation, stake-holder involvement, spot analysis etc
Explain that agile does not mean that DW is not needed.

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