On the Robustness of Temporal Properties for Stochastic Models

TitleOn the Robustness of Temporal Properties for Stochastic Models
Publication TypeConference Paper
Year of Publication2003
AuthorsBartocci E, Bortolussi L, Nenzi L, Sanguinetti G
Conference Name2nd International Workshop on Hybrid Systems and Biology, HSB 2013
PublisherOpen Publishing Association
Conference LocationTaormina, Italy
KeywordsComputational Systems Biology, Continuous Time Markov Chains, Gaussian Process Optimisation, Robust Semantics, Signal Temporal Logic, stochastic hybrid systems, System Design

Stochastic models such as Continuous-Time Markov Chains (CTMC) and Stochastic Hybrid Automata (SHA) are powerful formalisms to model and to reason about the dynamics of biological systems, due to their ability to capture the stochasticity inherent in biological processes. A classical question in formal modelling with clear relevance to biological modelling is the model checking problem. i.e. calculate the probability that a behaviour, expressed for instance in terms of a certain temporal logic formula, may occur in a given stochastic process. However, one may not only be interested in the notion of satisfiability, but also in the capacity of a system to mantain a particular emergent behaviour unaffected by the perturbations, caused e.g. from extrinsic noise, or by possible small changes in the model parameters. To address this issue, researchers from the verification com- munity have recently proposed several notions of robustness for temporal logic providing suitable definitions of distance between a trajectory of a (deterministic) dynamical system and the boundaries of the set of trajectories satisfying the property of interest. The contributions of this paper are twofold. First, we extend the notion of robustness to stochastic systems, showing that this naturally leads to a distribution of robustness scores. By discussing two examples, we show how to approximate the distribution of the robustness score and its key indicators: the average robustness and the conditional average robustness. Secondly, we show how to combine these indicators with the satisfaction probability to address the system design problem, where the goal is to optimize some control parameters of a stochastic model in order to best maximize robustness of the desired specifications.