Designing a Data Warehouse: Supporting Customer Relationship Management

LOGICAL SCHEMA

The implementation of true retrospection for any entity, attribute, or relationship requires that the existence of the lifespan of the object in question is recorded. This must be in the form of a period marking the starting and ending times. The introduction of such periods changes the structure of the entities. For instance, the customer circumstances from the Wine Club model has a requirement for true retrospection on its own existence as well as the relationship with the sales area and the customers' addresses. Each of these would be given their own existence period attributes as is illustrated in the diagram in Figure 6.2. Figure 6.2 shows how the implementation of true retrospection using existence attributes results in the ...