Timed Behavior Trees for Failure Mode and Effects Analysis of time-critical systems

Behavior Trees are a graphical notation used for formalising functional requirements, and have been successfully applied to several industrial case studies. However, the standard notation does not support the concept of time, and consequently its application is limited to non-real-time systems. To overcome this limitation we extend the notation to timed Behavior Trees. We provide an operational semantics which is based on timed automata, and thus serves as a formal basis for the translation of timed Behavior Trees into the input notation of the timed model checker UPPAAL. System-level timing properties of a Behavior Tree model can then be automatically verified using UPPAAL. Based on the notational extensions with model checking support, we introduce timed Failure Mode and Effects Analysis, a process for identifying cause-consequence relationships between component failures and system hazards in real-time safety critical systems.     

Model checking for process rewrite systems and a class of action-based regular properties

We consider the model checking problem for Process Rewrite Systems (PRS), an infinite-state formalism (non Turing-powerful) which subsumes many common models such as Pushdown Processes and Petri Nets. PRS can be adopted as a formal model for programs with dynamic creation and synchronization of concurrent processes, and with recursive procedures. The model-checking problem of PRS against action-based linear temporal logic (ALTL) is undecidable. However, decidability for some interesting fragment of ALTL remains an open question. In this paper, we state decidability results concerning generalized acceptance properties about infinite derivations (infinite term rewriting) in PRS. As a consequence, we obtain decidability of the model-checking problem (restricted to infinite runs) of PRS against a meaningful fragment of ALTL.