Time is treated in data modeling in two ways:
· In a conceptual, logical, or physical model, it usually shows up as attributes in transaction entity classes. In the model presented in this book, the attributes are usually limited to the Effective Date and Until Date, describing the duration when the (usually Activity, but not always) was taking place. If it is an Event, there would be a Transaction (or event) Date, instead.
In general, dates are not used for reference entities, although sometimes they are included as metadata to describe when the information was updated.
· In dimensional models, dates and their components are entity classes in their own right. These are not relevant for the Enterprise Model being presented ...