Architecture Modeling - SPES 2020

Architecture Modeling
Figure 5.7: Logical Perspective – Aircraft Level
To show the concept of contract-based design some components are annotated exemplary
with contracts using the satisfaction-link. Contracts are depicted throughout this example as a
pair of green and blue boxes where the green box contains the strong assumption As and the blue
box the guarantee G. The weak assumption Aw is for this and the following figures always true
and thus not shown explicitly. To be able to reference contracts, each contract has an identifier
annotated in the upper left corner. For example, C1 claims that if the assumption that the
pedalPosition is within certain bounds is fulfilled, it is guaranteed that meterControl
always occurs within an interval of 0 and 4 milliseconds after pedalPosition has occurred.
Furthermore, it is guaranteed that meterControl is again within certain specified bounds.
Technical Perspective While staying at the same abstraction level, we will now have a look
at the technical perspective (as introduced in Section 3.2.4) of the system in Figure 5.9. Here,
the BSCU is shown again on the left hand side as a computing resource. In contrast to the logical
perspective where actuators are modeled as one logical component, in the technical perspective
there are the actual hydraulic actuators modeled as actuator components and their driver units as
computing resources. The driver units mainly have the task to transform the BSCU commands
to signals the actuator can handle. In this snapshot MeterValveCtrl is an example for a
driver unit forwarding signals to the actuator MeterValveActuator. As before, on this
perspective some components are annotated with contracts derived from the contracts on the
logical perspective. How to check if these contracts match is shown in Section 5.1.3.3.
Decomposition Next, we demonstrate the design step of decomposition (as introduced in
Section 4) at the example of the BSCU component in the logical perspective of the System Level
which is depicted in Figure 5.10. The BSCU is decomposed into a Monitor and a Command
component in order do divide the functionality into two different logical units. The Monitor
component observes the state of the system and detects inconsistencies. The Command unit
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