IBM SG24-7368-00 manual Mdsd and SysML

￿The Processing Unit communicates with the RainSensor using a flow port. The data exchanged is two bitstreams, one containing the measurements from the sensor and another containing synchronization data. The port is typed with a specification of these flows using the element SensorECUCommunication (see Figure 7-6). Notice the direction of the flows in the definition.

￿For convenience a flow port can be conjugated in the sense that its input and outputs are inversed (flows declared as in becomes out and vice-versa) with respect to the definition of the interface. This is useful when connecting two systems whose flow ports are conjugated with respect to each other. This is the case for instance between the Processing Unit and the RainSensor in

Figure 7-5.A conjugated flow port is represented in black. Because the synchronization data flow is declared as inout, the conjugation of the port has no effect on it.

￿Note that in Figure 7-5connectors between ports link parts defined within the block. SysML actually allows direct connection between ports defined at

different levels of granularity, for example between a port and another one defined inside a part. This type of connector are called nested connectors. We refer readers to the standard specification [OMG SysML] for more details about these connectors.

￿Flow ports are also useful to define physical contact between parts: For example the Sensor Attachement unit is fixed to the Windshield using an adhesive. The block representing the adhesive material AttachementAdhesive (Figure 7-6)is used to type the flow port connecting these parts.

The addition of flow ports to SysML allows us to reason more effectively about physical or electrical design issues. UML does not do this without inventing a stereotype or extension which would provide the equivalent semantics.

Chapter 7. MDSD and SysML 155