On human-centred security: a new systems model based on modes and mode transitions

Abstract We propose an abstract conceptual framework for analysing complex security systems using a new notion of modes and mode transitions. A mode is an independent component of a system with its own objectives, monitoring data, algorithms, and scope and limits. The behaviour of a mode, including its transitions to other modes, is determined by interpretations of the mode’s monitoring data in the light of its objectives and capabilities—these interpretations we call beliefs. We formalise the conceptual framework mathematically and show how to quantify and visualise beliefs in higher-dimensional geometric spaces. The mathematical models are based on simplicial complexes. Our theoretical models are intended to help design, analyse, evaluate and explain systems that provide human-centred services facilitated by software, when confronted by critical security situations, both human and digital.