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Block, OSL and MSL Safety Argument Modules. 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

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Presentation Transcript
overview
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, onlythat 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

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block osl msl module interface
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

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guarantee is assured
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

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guarantee is assured1
Guarantee is assured
  • Each dependency at each level must be satisfied
  • This is done by the Guarantees of other modules

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guarantee is assured2
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...

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process argument
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

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