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Safety 4.0 project

Guidelines on demonstrating safety of novel subsea technologies: Part IV – Developing a safety argument

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This document intends to give guidance about how to demonstrate the safety of complex systems. 

The reader should get an understanding of why

  • complex systems require a different approach compared to simple systems 
  • quantitative reliability does not represent safety adequately in complex systems 
  • different system models must be used in the analyses of complex systems 
  • a systems approach is necessary to understand the behaviour of complex systems 
  • objectivity is essential in handling any system artefact 

The reader should get an understanding of what: 

  • kind of assurance aspects are essential for creating confidence that the systems behave safely 
  • kind of system aspects must be addressed to understand system behaviour, that is, according to the “CESM metamodel” 
  • kind of capability any analysing method should possess when dealing with complex systems. 
  • a safety argument is 

The reader should get an understanding of how

  • complex systems differ from simple systems 
  • complexity arises in systems 
  • analysis of the behaviour of complex systems at different levels of abstraction can be done to identify: 
    • safety requirements 
    • scenarios for how systems may become unsafe 
  • to merge the above requirements with safety requirements originating from regulations 
  • objectivity, knowledge, and arguments are related 
  • evidence and reasoning can build knowledge to underpin the truthfulness of claims 
  • grounds for justified confidence can be created to show that the: 
    • identified requirements are adequate 
    • requirements are fulfilled.