Confidence arguments help to justify that main arguments in assurance cases are sound and trustworthy. While the main argument directly addresses system safety or security, the purpose of the confidence argument is to answer the question why we should trust that the main argument is right. Some standards and guidelines, and also some certifiers require […]
Assurance cases are used not only during system development but also during operation. For many systems, Safety Performance Indicators (SPIs) are used in this context. They are used to monitor and report the system safety performance over time. They help to identify whether safety goals are being achieved and provide early warning signals of emerging […]
Strong assurance cases are achieved by building confidence in the validity of reasoning steps and demonstrating how defeaters are handled. These two approaches present two different directions of argumentation. The first one focuses on providing sound basis for the argument while the second aims at defending it against known defeaters. Which approach is more effective […]
An assurance case is a structured argument supported by evidence. It can a static safety case referring to static evidence and frozen in a Safety Case Report. And it can a dynamic object referring to dynamic evidence that can evolve. For example the evidence may include Safety Performance Indicators based on measurements during system operation. […]
Editing GSN arguments in PREMIS is now easier, you can drag elements from the tray directly to the diagram. At the same time, the performance of GSN diagrams in the new version of PREMIS has been improved. Especially generating diagrams is now very fast. The new version also includes improvements in the management of assessments, […]
Both the GSN Community Standard and OMG SACM specify modular assurance cases, though from different perspectives. The GSN Standard focuses on the logical dependencies between elements in different argument modules. SACM, on the other hand, introduces the concepts of interfaces and bindings in its metamodel. In practice there are no conflicts between the two […]
Both system safety and security are critical goals, but they are not always compatible. You have to consider safety – security relations when developing a system assurance case. A solution to this problem, a Safety-Security Assurance Framework (SSAF), has been proposed by the latest publication of the SCSC Security Informed Safety Working Group. The main […]
Chat in the team working on the assurance case improves cooperation and enables easy exchange of information directly in the tool. Discussion is naturally connected to the places of argumentation that it concerns and where changes are introduced. Adding priorities to the chat allows to highlight the main threads of conversation for efficient development of […]
Argument building blocks were originally proposed for CAE assurance cases, but the approach is applicable to all types of assurance cases. The building blocks approach says that there are five types of possible support for a claim – you can provide supporting evidence or use one of four types of strategy: decomposition, substitution, concretion or […]
Improved assurance case development in GSN diagrams and automatic layout are the main enhancements in the new PREMIS version released last week. It is now easier to work with diagram pages, which no longer have a size limit. Editing diagrams is faster, navigation has been improved and working with GSN is now more effective. Now […]
We are working on extending GSN patterns with references to system context models. GSN patterns support argument abstraction but the details of how it works are not specified. You can specify a claim “{System S} is sufficiently safe”, but the GSN standard doesn’t say how to manage the parameter S. You can find some guidance […]
Until now, modular assurance cases in PREMIS could only be developed from the bottom up. That is, you had to develop the argumentation of all the modules, create interfaces, assign argument elements to the interfaces, and finally bind the modules. The result can be presented in an architecture diagram. This was a long and tedious […]