The traditional approach to regulatory approval or certification is the preparation of a safety case for a system in a specific configuration. A modular approach to safety case design means that new configurations can be created without the need to completely rework the whole safety case.
Modular design brings a number of benefits:
- Flexibility – introduce or substitute modules of different functionality.
- Cost savings – design a module once and reuse across many systems.
- Ease of maintenance – updates confined to a constituent component or module of the system.
The benefits of modular design are further extended when one considers that the constituent components or modules of a system are often designed by different departments, or by third party organisations that make up the supply chain.
Modular GSN in ASCE
The GSN community standard version 3 specifies the extension to GSN that enables organisations to design safety cases using a modular approach.
This extension to GSN known as Modular Extension, is fully incorporated into an easy to use add-on for ASCE allowing organisations to manage complex safety cases in a straightforward way.
The benefits of adopting the ASCE Modular GSN extension for safety case design include:
- Implementation of the symbology of Modular GSN Extension.
- Updates that keep pace with significant changes in GSN 3 community standard.
- Additional features to improve referencing and navigation of the safety arguments.
- A new package view in which to present the architecture of your system safety case.
- Additional options to clearly define module interfaces and automatically update links between argument modules.
- Reducing the amount of safety case modification as a result of system changes.
- Logical separation of issues that can be developed by stakeholders.
New to modular approach?
We offer a bespoke consulting program for users new to partitioning a safety argument using the Modular GSN approach, or for those looking for guidance in best practice.
Architecture View
The ASCE Modular GSN extension supports Architecture view representing the highest level of system hierarchy.
This view allows users to specify the modules and contracts that will exist within the safety case. For users at an early stage of design, the package view is the ideal environment to sketch out the intent of the safety case. This is especially useful as visualising the modules, even though they may not yet exist, is often a catalyst for further discussion.
Authored dependency links can be created to convey how the modules will eventually be linked.
As the safety case design progresses, each module within the package view will be linked to an actual module with its own ASCE file. Within each module the content is created in a similar way to normal GSN construction.
Using the modular GSN symbology users now have the benefit of linking elements across the module boundaries. In this way a set of relationships or actual dependencies are created between the modules.
A rescan feature can be used to discover the actual dependencies between modules in the safety case. Once discovered they can be compared to the authored dependencies (the intent) as specified at the project start.
Modular Extension symbology in ASCE
The following symbology is implemented within the ASCE Modular GSN extension:
- Goal – a public goal that may be referenced from other modules.
- Context – a public context that may be referenced from other modules.
- Away Goal – a reference to a goal contained in another module.
- Away Context – a reference to a context contained in another module.
- Away Solution – repeats a reference to evidence items presented in another argument module.
- Away Justification – repeats a justification presented in another argument module.
- Away Assumption– repeats an assumption presented in another argument module.
- Module Reference – a reference to a remote module.
- Contract Reference – a reference to a remote module that is a Modular GSN contract.
- Goal solved by Contract – goal to be supported by a Modular GSN contract, which is not yet specified.
Beyond core support to the GSN version 3 standard, ASCE offers additional elements, decorators, and features, equipping users with a wide range of valuable tools for comprehensive assurance case development and maintenance.
