The personification of reliability, safety, and security

Crash dummies have been used for many years to evaluate the safety and crash worthiness of automobiles and other vehicles. The dummies provide a way of measuring the ergonomics of the automobile's design and also the impact of a crash on the vehicle occupants. Personas serve the same purpose for software systems. A persona represents a certain type of user; however it goes beyond a user's physical characteristics to also include the user's attitudes and goals as well as how they will interact with the system. Personas have traditionally been used to represent a broad segment of system users and personalize the design of the user interface for that subset of users. In this paper we show how the use of personas can be extended to evaluate several aspects of system security, safety, and reliability. First, when eliciting system requirements, personas serve as the basis for evaluating the effects of system vulnerabilities identified in UML use-cases. Second, personas are used to determine work loads and operational profiles, which, in turn, determine the execution times for various system functions, and ultimately to allocate reliability requirements and the amount of testing needed to achieve that reliability among the system modules. The use of a persona for these tasks brings both realism and specificity to these tasks that cannot be achieved using a generic "user".