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The model of the mobile workforce application is getting more accurate and complete by the week. Jan and I go over refinements that he has made since the last session. In particular, he presents an optimization that he made to bring two concepts together into one fact.

Application designers will often try to minimize the number of concepts within a model. In the name of reuse, they optimize the number of tables in the database or the number of classes. If the same class or table is used for two different concepts, then the model risks allowing invalid states and not representing either one very well. Look for relationships that are only used in certain situations. They might be a red flag for overloading.

Next, we examine the user authorization model and identify some potential improvements. All applications in a historical model are multi-tenant.
User identity is independent of tenant. By modeling the relationship between a user and a tenant, we can assign roles unique to each tenant. Tenants authorize users within their own organization.

Finally, we look at how the model applies the Period pattern. This pattern takes advantage of clocks within the model to subdivide history by time. But the periods at which different stages of a process take place could differ. Jan and I explore the ways in which periods apply to phases of a workflow, and change from one phase to the next.