Contradictions Identification of Safety and Security Requirements for Industrial Cyber–Physical Systems

Industrial cyber–physical systems (iCPSs) are the backbone of the fourth industrial revolution, facing more safety and security (S&S) challenges compared to traditional industrial systems. One of the most critical challenges is the collaborative analysis of S&S. Considerable efforts have been made toward integrating S&S and resolving their contradictions. However, a significant research gap remains regarding the accurate definition of contradictions in S&S requirements, along with an identification methodology. This study presents a systematical methodology to address this challenge. We propose two sufficient conditions that result in contradictions and provide algorithms to help their identification. Additionally, three measures have been proposed to reduce the difficulty of contradictions identification, including a conceptual model for iCPSs with S&S objectives to constrain objects and interactions within the model, a method for unifying the elicitation of S&S requirements, and a requirements template for coordinating the representation of S&S requirements. To provide insight into the operations of the methodology, we demonstrate its application in a smart factory. The results show that this approach can effectively identify the hidden contradictions in S&S requirements.