11.4 Avionics_System.aadl
This is the partition model of the Rockwell Avionics system from the tutorial to perform partition-based latency analysis.  The model shows 4 systems and the display as device. It defines a flow from the display through the Display Manager, Page Content Manager, Flight Manager to the Flight Controller and back. The flow is defined by providing flow specs for each system component, by defining the connections between the subsystems, and by specifying an end-to-end flow as described.  The flow latency analysis determines a lower bound on latency based on the fact that cross-partition communication implies a minimum latency of the partition execution rate for each cross partition step.  We have specified a Partition_Period property for the rate.  The end-to-end flow has an expected latency property value of 300 ms.  This is exceeded by the flow. Since we know that this is a lower bound, we can conclude two things. First, the only way to reduce latency is to reduce the number of partition crossings, e.g., by connecting the flight director directly to the page content manager instead of via the flight manager.  Second, the lower bound of latency implies an upper bound on the rate at which the display request events can occur.  This allows scheduling analysis to become more realistic.
11.4.1 Running the Example
Compile into XML. Open the aaxl file. Select any object in the model and invoke the flow analysis.  The “Problems” View will show the result of the analysis—the expected latency being exceeded.