My first Publication Agile-Data-Warehouse-Design-eBook | Page 66

Modeling Business Events 45 Discrete Event By a process of elimination, if an event is neither recurring nor evolving, it must be discrete. You reconfirm this each time you discover a new detail by asking if its example values can ever change. If details never change, or changes are handled as new adjustment events, then the event remains discrete. In Figure 2-7 both the ORDER DATE and the DELIVERY DUE DATE (if applicable) are known at the time of an order and do not change, so the order events, as modeled so far, are discrete. Discrete events contain details that do not change Who? Once you have identified the story type it’s time to double-back (to the top of the 7Ws flowchart in Figure 2-2) and find out whether any other whos are associated with the event. The general form of a who question is “Subject Verb Object from/for/with who?” Using the current subject, verb and object you might ask: Ask a who question to see if anyone else is involved CUSTOMER orders PRODUCT from whom? To which the stakeholder might reply: Salesperson If so, you add the new who to the table and ask for example salespeople to match the existing event stories. E.g., to continue a group themed story you might ask: Is there always just one SALESPERSON responsible for the order? In Figure 2-8, the event stories introduce you to some of Pomegranate’s finest sales personnel, but also shows that orders can be made without a salesperson, and that some orders are handled by sales teams rather than individual employees (continu- ing the group story theme). Figure 2-8 Adding a second who detail