Extending UML sequence diagrams to model trust-dependent behavior with the aim to support risk analysis

UML sequence diagrams are intuitively simple and can be understood by most stakeholders, including end-users, decision makers, engineers and other parties involved in a risk analysis. Building on UML sequence diagrams and trying to maintain their intuitive simplicity, we propose a language for modeling systems where the trust considerations of actors play a major role. Trust considerations are integrated with behavioral descriptions in order to facilitate analysis of the trust considerations of the actors, as well as their resulting behavior. We claim that our language allows trust dependent behavior to be described at a level of abstraction suitable for communication between different groups of stakeholders in a risk analysis situation. Furthermore, we argue that the increased expressiveness is required to facilitate the kind of analysis necessary to properly weigh and treat trust dependent risk behavior.