What is GSN?

GSN (Goal Structuring Notation) is a graphical argumentation notation to explicitly document the individual elements of arguments. Elements are such things as goals, solutions, contexts and their relationships. Documenting and visualizing the arguments with this graphical notation can help provide assurance of critical properties of systems, services, organizational safety and security and any other properties to bring the best and proper solutions.

One of the common usages of GSN is for Safety Cases. Safety Cases are structured arguments supported by evidences to demonstrate that a given system is acceptably safe in a given context. The Safety assurance has been regulated in several fields including railways and aviation. GSN can be also effectively used for ISO 26262, the functional safety standard for road vehicles to define safety goals and functional safety requirements.

With GSN, you will first define a top goal and then break it down to other, lower level, goals. These lower level goals are essential to achieve the top goal and build the structure hierarchically. If there are no more goals to break down, you can indicate so using the element called "Solutions". Also GSN has additional elements such as "Strategy", "Assumptions", "Justifications" and "Context" to give important information to visualize the structure of arguments. This makes it easier to find lack of information and evidence that is not convincing enough. GSN is also helpful in explaining the arguments to third parties. Therefore, GSN can be used not only for Safety cases but also for Security, Dependability and in any general arguments.

Sample GSN Diagram (Figure 6 from GSN Community Standard)

Goal Structuring Notation
*Astah GSN was made in collaboration with AIST