Assurance Case Arguments in the Large: The CERN LHC Machine Protection System

Most public assurance arguments are used to introduce, discuss, and present novel concepts and techniques related to structured argumentation. These examples often rely on generic claims such as “All hazards have been identified” and generic patterns of reasoning and are quite different from their fully developed industrial counterparts. This practical experience report describes a medium-size assurance case argument for the CERN Large Hadron Collider Machine Protection System expressed using Eliminative Argumentation. This assurance case with 509 nodes was created in approximately three months, validated in collaboration with CERN experts, and is now publicly available. We also report on our practical experience in creating this argument and reflect on the support provided by the features of the collaborative assurance case editor we used called Socrates.