BraceAssertion: Runtime Verification of Cyber-Physical Systems

Xi Zheng, Christine Julien, Rodion Podorozhny, Franck Cassez

Abstract:

Cyber-Physical Systems (CPS) have gained wide
popularity, however, developing and debugging CPS remain
significant challenges. Many bugs are detectable only at runtime
under deployment conditions that may be unpredictable or at
least unexpected at development time. The current state of the
practice of debugging CPS is generally ad hoc, involving trial and
error in a real deployment. For increased rigor, it is appealing to
bring formal methods to CPS verification. However developers
often eschew formal approaches due to complexity and lack of
efficiency. This paper presents BraceAssertion, a specification
framework based on natural language queries that are auto-
matically converted to a determinitic class of timed automata
used for runtime monitoring. To reduce runtime overhead and
support properties that reference predicate logic, we use a second
monitor automaton to create filtered traces on which to run
the analysis using the specification monitor. We evaluate the
BraceAssertion framework using a real CPS case study and show
that the framework is able to minimize runtime overhead with
an increasing number of monitors.