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2014 Technical Reports

Using Indexed and Synchronous Events to Model and Validate Cyber-Physical Systems

Chen-Wei Wang, Jonathan S. Ostroff and Simon Hudon

Technical Report EECS-2014-03

York University

June 30 2014


Timed Transition Models (TTMs) are event-based descriptions for modelling, specifying, and verifying discrete real-time systems. A system is composed of module instances. Each module declares an interface and a list of events. An event can be spontaneous, fair, or timed (i.e., with lower and upper time bounds). TTMs have a textual syntax, an operational semantics, and an automated tool, including an editor with type checking, a graphical simulator, and a veri er for linear-time temporal logic. In this paper, we extend TTMs and its tool with two novel modelling features: synchronous events and indexed events. Event synchronization allows developers to decompose simultaneous state updates into actions of separate events. To specify the intended data ow among synchronized actions, we reference the post-state (i.e., one resulted from taking the synchronized actions) using primed variables. The TTM tool automatically infers the data ow from synchronous events, and reports type errors when there are inconsistencies due to circular data ow. We apply synchronous events to verify function blocks from the IEC 61131 standard, and a part of the requirements of a nuclear shutdown system. Indexed events allow for concise description of behaviour common to a (possibly unspecified) set of actors. The indexing construct allows us to select a specific actor and specify a temporal property for that actor. We use indexed events to verify a mutual exclusion protocol and a train system. In all examples, the TTM tool is used to verify safety, liveness, and real-time properties.

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