A Methodology for Exposing Risk in Achieving Emergent System Properties

Abstract

Determining whether systems achieve desired emergent properties, such as safety or reliability, requires an analysis of the system as a whole, often in later development stages when changes are difficult and costly to implement. In this article we propose the Process Risk Indicator (PRI) methodology for analyzing and evaluating emergent properties early in the development cycle. A fundamental assumption of system engineering is that risk mitigation processes reduce system risks, yet these processes may also be a source of risk: (1) processes may not be appropriate for achieving the desired emergent property; or (2) processes may not be followed appropriately. PRI analyzes development process artifacts (e.g., designs pertaining to reliability or safety analysis reports) to quantify process risks that may lead to higher system risk. We applied PRI to the hazard analysis processes of a network-centric, Department of Defense system-of-systems and two NASA spaceflight projects to assess the risk of not achieving one such emergent property, software safety, during the early stages of the development lifecycle. The PRI methodology was used to create measurement baselines for process indicators of software safety risk, to identify risks in the hazard analysis process, and to provide feedback to projects for reducing these risks.