1. Industrial Avionics Working Group 19/04/07 Block, OSL and MSL Safety Argument Modules

2. Industrial Avionics Working Group 19/04/07 Overview Block, OSL and MSL Modules provide the same top-level goal –“{Guarantee X} is sufficiently assured” Saw how Block must guarantee certain behaviour to support the SR module OSL, and MSL must similarly guarantee certain behaviour to support other modules Note that these Modules don’t need to argue these guarantees are safe, only that they are provided Again there are two main claims supported in these Modules: –Each Guarantee is assured Product Argument –The process used in implementing the guarantees is adequate Process Argument

3. Industrial Avionics Working Group 19/04/07 Block/OSL/MSL Module Interface Module is again split into two with the process argument contained within the product argument Product argument provides the following public goal to other argument modules This goal would be referenced when another module requires the guaranteed service The following goal requires support from other Modules Note that dependencies may be identified at many different development levels

4. Industrial Avionics Working Group 19/04/07 Guarantee is assured The argument can be made by mapping the Guarantee down through each level of development Once down to code level can appeal directly to test and verification evidence At each level new dependencies may be identified which must be satisfied Dependencies for each Guarantee are identified in DGRs

5. Industrial Avionics Working Group 19/04/07 Guarantee is assured Each dependency at each level must be satisfied This is done by the Guarantees of other modules

6. Industrial Avionics Working Group 19/04/07 Guarantee is assured A SC contract must be formed with each of the Modules whose guaranteed behaviour is required to support a dependency The Blocks may, for example, have dependencies supported by the OSL, the OSL by the MSL and so on...

7. Industrial Avionics Working Group 19/04/07 Process Argument The process argument must cover all aspects of the development process –Including the DGR process For each aspect of the process it must be shown that it is adequate and followed