Suggested changes to FunctionalDevice. 27 3 Modeling Concepts for Supporting the Analysis of Behavior-Centric Properties 29 3.1 Background 29 3.2 EAST-ADL Enhancement Proposals 31
Suggested changes to FunctionalDevice. Since Hazards occur when a failure is propagated to the output of an actuator in a specific situation, they all originate through the output of a FunctionalDevice acting as an actuator. But an instance of a FunctionalDevice can be both sensor and actuator and there is no distinction that makes it possible to find locations in a model where propagated failures can cause hazards. Hence it might make more sense to use the roles ‘logical’ and ‘physical’ for the ports on a functional device to state where it is connected. The direction of the physical port could then indicate whether it is a sensor or actuator when an analysis is performed. The difference between a functional device and an analysis function could be seen as the fact that the functional device has a connection to the physical world, something that an analysis function cannot have. The suggested change to the FunctionalDevice class is a new port. The connection to the physical world, the place where hazards occur or where sensors are connected: Associations physicalPort : FunctionPort [*] (from FunctionModeling) This could be both a FlowPort or PowerPort depending on the needs. This port serves two purposes in the analysis of models. It gives information on the type of functional device given the direction of the port. Secondly it serves as the connection point between Safety goals and the logical architecture, through the error model. The current port given by the FunctionType attribute ‘port’ would then be limited to being logical ports not allowed to be connected to the environment. Depending on the type of functional device input ports would be stimuli from the logical world and outputs could be nominal values or logical feedback. This enables the possibility to make functional devices hierarchical as the internal structure could feed not only the physical port with data but also the logical ports which makes it perfectly plausible to use AnalysisFunctionTypes in the decomposition of a FunctionalDevice. Having the capability to do logical feedback would make it possible to address safety mechanisms as there would be a logical path that could be specialized when decomposing the functional device in a more detailed view. Functional devices can be seen as either very complex system, especially if you are focusing on them in your modeling. Or as trivial data producers if you are interested in the logic manipulating of data.
