13.8. What's the Connection Between SSDs, System Operations, and Layers?
During analysis work, we sketched some SSDs for use case scenarios. We identified input events from external actors into the system, calling upon system operations such as makeNewSale and enterItem .The SSDs illustrate these system operations, but hide the specific UI objects. Nevertheless, normally it will be objects in the UI layer of the system that capture these system operation requests, usually with a rich client GUI or Web page.In a well-designed layered architecture that supports high cohesion and a separation of concerns, the UI layer objects will then forwardor delegatethe request from the UI layer onto the domain layer for handling.Now, here's the key point:
The messages sent from the UI layer to the domain layer will be the messages illustrated on the SSDs, such as enterItem . |
Figure 13.8. System operations in the SSDs and in terms of layers.
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