My first Publication Agile-Data-Warehouse-Design-eBook

5 M ODELING S TAR S CHEMAS We are all in the gutter, but some of us are looking at the stars. — Oscar Wilde In this chapter we describe the star schema design process for converting BEAM ✲ models into flexible and efficient dimensional data warehouse models. This chapter is a The agile approach that we take begins with test-first design, by using data profiling techniques to verify the BEAM ✲ model against the data available in source sys- tems. This results in an annotated model which documents source data characteris- tics and issues. This is used for model review with stakeholders and development sprint planning with the DW/BI team. Verifying BEAM✲ Next, the revised BEAM ✲ model is translated into a logical dimensional model by adding surrogate keys. The resulting facts and dimensions are documented by drawing enhanced star schemas using a combination of BEAM ✲ and ER notation. Converting BEAM✲ Finally, the star schemas are used to generate physical data warehouse schemas which are validated by BI prototyping and documented by creating a physical dimensional matrix. Validating DW Data profiling to verify stakeholder data requirements Annotating BEAM✲ models with data sources and profile metrics guide to: models against available data sources models into star schemas designs by prototyping Chapter 5 Topics At a Glance Reviewing annotated models and planning development sprints Converting BEAM✲ models into logical/physical dimensional models The importance of data warehouse surrogate keys Designing for slowly changing dimensions Defining additive facts Drawing enhanced star schema diagrams and creating physical schemas BI Prototyping to validate dimensional models Creating a physical dimensional matrix 129

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