Now, let's create the logical data models of TaskAgile. In this stage, we will add attributes to each type of entity in the conceptual data model by going through user stories by theme and implementing the relationships between entities, as well as the subtypes we used.
Based on Users theme and Teams theme, we create the following logical data models:
Figure 5.20: Logical data model of User and Team entities
As you can see in Figure 5.20, for User entities, we use surrogate key ID as its primary key because even though Email Address and Username can be used to identify a user, they can be changed. The system-generated ID will always stay the same. It is the same for Team entities. And the User ID attribute in the Team Creator entities is a foreign key. In the diagram, PK is short for Primary Key, and FK is short for Foreign Key. And, in Team Creator entities, the Team ID and User ID attributes form a composite key that can be used to uniquely identify a Team Creator.
Based...