The Goal Structuring Notation – A Safety Argument Notation

In Europe, over recent years, the responsibility for ensuring system safety has shifted onto the developers and operators to construct and present well reasoned arguments that their systems achieve acceptable levels of safety. These arguments (together with supporting evidence) are typically referred to as a “safety case”. This paper describes the role and purpose of a safety case. Safety arguments within safety cases are often poorly communicated. This paper presents a technique called GSN (Goal Structuring Notation) that is increasingly being used in safety-critical industries to improve the structure, rigor, and clarity of safety arguments. The paper also describes a number of extensions, based upon GSN, which can be used to assist the maintenance, construction, reuse and assessment of safety cases. The aim of this paper is to describe the current industrial use and research into GSN such that its applicability to other types of Assurance Case, in addition to safety cases, can also be considered.