UML14 — Using or implementing an interface of a Subsystem

Problem: The specification part of the UML Subsystem element does not consider the two ways to make use of an interface: 1.) Direct calls. When a client subsystem should invoke operations of the subsystem. 2.) Notifications (extensions). When a client subsystem should receive notifications from the subsystem.

Note that the static dependency can be directed the same way in both cases, but a call can either propagate along or against the dependency, depending on what subsystem that is implementing the interface. One-way static dependencies are crucial when a system should be easy to maintain. Therefore, one should distinguish between if a client needs to invoke an operation of the subsystem (implemented by the subsystem) or if the client should implement the interface in order to be notified by the subsystem. If needed, I can provide more information about how this can be seen.

Suggestion: I introduced a usage dependency from the subsystem border to the interface in order to show that the subsystem provides and uses an interface which is to be implemented by a client subsystem that is to receive notifications.

Background: I have been involved in different projects for Ericsson (the Telecom Business) and for the Swedish Airforce Defence Industry. Basically, the Subsystem modelling element is of great help when modelling large complex systems, such as Telecom systems for Radio Network Management. These systems do not only require robust software architectures, their architectures have to be considered on different architectural levels in order to reduce complexity. Also, the Subsystem modelling element is of great help when delegating and managing responsibility.

No Data Available