We advocate the increased real-time monitoring of software by software. Only third-party monitors increase the trust in the monitored software, and only low-overhead monitors are widely acceptable. These restrictions have technical consequences. Third-party monitors cannot instrument the monitored source code. Low-overhead monitors must be best-effort so not to slow down the monitored software. We build a theoretical framework and corresponding middleware for the online black-box monitoring of quantitative software properties, such as average or maximal response time of a server, or algorithmic fairness in decision making. Unlike static verification, which answers reachability queries for programs, monitoring is runtime verification, which answers membership queries for observed program behaviors with regard to a given formal specification. Our monitors are not necessarily finite-state, and their verdicts may be approximate or probabilistic. This allows for a rich spectrum of cost-precision-confidence trade-offs in monitoring.
Tom Henzinger is Professor at the Institute of Science and Technology Austria (ISTA). He holds a Ph.D. degree in Computer Science from Stanford University (1991). He was Assistant Professor of Computer Science at Cornell University, Professor of Electrical Engineering and Computer Sciences at the University of California, Berkeley, Director at the Max-Planck Institute for Computer Science in Saarbrücken, Germany, and Professor of Computer and Communication Sciences at EPFL in Lausanne, Switzerland. From 2009 until 2022, he was the founding president of ISTA in Klosterneuburg, Austria. His research focuses on the theory of software systems, especially models, algorithms, and tools for the design and verification of reliable software systems. His HyTech tool was the first model checker for mixed discrete-continuous systems. He is a member of the US National Academy of Sciences, Academia Europaea, the German Academy of Sciences (Leopoldina), and the Austrian Academy of Sciences. He is a Fellow of the AAAS, the ACM, and the IEEE. He received the Robin Milner Award of the Royal Society, the EATCS Award of the European Association for Theoretical Computer Science, and the Wittgenstein Award of the Austrian Science Fund.