Software Assurance in an Uncertain World

From financial services platforms to social networks to vehicle control, software has come to mediate many activities of daily life. Governing bodies and standards organizations have responded to this trend by creating regulations and standards to address issues such as safety, security and privacy. In this environment, the compliance of software development to standards and regulations has emerged as a key requirement. Compliance claims and arguments are often captured in assurance cases, with linked evidence of compliance. Evidence can come from testcases, verification proofs, human judgment, or a combination of these. That is, experts try to build (safety-critical) systems carefully according to well justified methods and articulate these justifications in an assurance case that is ultimately judged by a human. Yet software is deeply rooted in uncertainty; most complex open-world functionality (e.g., perception of the state of the world by a self-driving vehicle), is either not completely specifiable or it is not cost-effective to do so; software systems are often to be placed into uncertain environments, and there can be uncertainties that need to be We argue that the role of assurance cases is to be the grand unifier for software development, focusing on capturing and managing uncertainty. We discuss three approaches for arguing about safety and security of software under uncertainty, in the absence of fully sound and complete methods: assurance argument rigor, semantic evidence composition and applicability to new kinds of systems, specifically those relying on ML.