I have a system that is divided into partitions (avionics system). THe basic means of sending and receiving information is via read and write calls to a certain port. The reading and writing is handled by the Real-Time Operating System (RTOS).

Partition A must send some data to Partition B. One could draw a sequence diagram with two lifelines representing the two partitions, and then a message between the two. However, the semantics of UML which is more object-oriented, are more like partition A invoking an operation on partition B. This may help in sketching something and usually most people would understand it. However, are there other ways to sketch this? I thought about putting the RTOS as a lifeline, but then that leads to clutter and it takes away from the inter-partition communciation focus, because now the two partitions are decoupled, which reflects reality, but diagramatically, there is a third lifeline.

I have a system that is divided into partitions (avionics system). THe basic means of sending and receiving information is via read and write calls to a certain port. The reading and writing is handled by the Real-Time Operating System (RTOS).

Partition A must send some data to Partition B. One could draw a sequence diagram with two lifelines representing the two partitions, and then a message between the two. However, the semantics of UML which is more object-oriented, are more like partition A invoking an operation on partition B. This may help in sketching something and usually most people would understand it. However, are there other ways to sketch this? I thought about putting the RTOS as a lifeline, but then that leads to clutter and it takes away from the inter-partition communciation focus, because now the two partitions are decoupled, which reflects reality, but diagramatically, there is a third lifeline.