My first Publication Agile-Data-Warehouse-Design-eBook | Page 69

48 Chapter 2 If you find yourself generalizing several details you should ask questions about how similar the event stories really are. If stories have very different details you will probably want to model them in separate event tables, because highly generalized events rapidly become meaningless to stakeholders. Figure 2-9 Adding where details Check that each where is a detail of “who does what” not just who or what When you ask for additional where details emphasize that you are looking for locations that are specific to the whole event, not the existing who or what details. This helps avoid (for the moment) detail about detail — like customer address and product manufacturing address — that are not dependent on the event. These reference addresses will be modeled as dimensional attributes of CUSTOMER and PRODUCT once the event is complete (see Chapter 3). Each time you finish collecting a W-type, it’s good practice to quickly scan through the previous Ws to check for missing details. After you finish asking where questions check to see if any of the where details remind the stakeholders of additional whos, whats and whens. Modelstorming with Whiteboards Whiteboards are the agile practitioner’s favorite collaborative modeling tool. They are ideal tools for modelstorming snippets of your design at a time but even the most generous whiteboards can be challenged by the width of a full BEAM✲ table. Here’s some practical advice for using them and other tools for event modeling: Use “whiteboard on a roll” plastic sheets to extend/replace your finite white- board. Large post-it™ notes or flipchart paper and masking tape work too but are not so neat or forgiving for iterative design. Sheets with a 2.5cm grid work very well for event tables.