Statecharts: A visual formalism for complex systems
Science of Computer Programming
Safeware: system safety and computers
Safeware: system safety and computers
The STATEMATE semantics of statecharts
ACM Transactions on Software Engineering and Methodology (TOSEM)
What is in a Step: On the Semantics of Statecharts
TACS '91 Proceedings of the International Conference on Theoretical Aspects of Computer Software
A Comparison of Statecharts Variants
ProCoS Proceedings of the Third International Symposium Organized Jointly with the Working Group Provably Correct Systems on Formal Techniques in Real-Time and Fault-Tolerant Systems
Safecharts for Specifying and Designing Safety Critical Systems
SRDS '99 Proceedings of the 18th IEEE Symposium on Reliable Distributed Systems
Model Checking Safety-Critical Systems Using Safecharts
IEEE Transactions on Computers
Modeling and verification of safety-critical systems using safecharts
FORTE'05 Proceedings of the 25th IFIP WG 6.1 international conference on Formal Techniques for Networked and Distributed Systems
Modeling and automatic failure analysis of safety-critical systems using extended safecharts
SAFECOMP'07 Proceedings of the 26th international conference on Computer Safety, Reliability, and Security
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Safecharts [2] are a safety oriented variant of Statecharts [3] and have been developed especially for the use in specification and design of safety critical systems. One of the fundamental aspects of Safecharts is the explicit ordering of system states according to their risk levels. Based on this ordering, transitions are classified according to the nature of their risk and are given a priority scheme favoring the execution of safer transitions in the event of any nondeterminism. As a precaution, transitions between states with unknown relative risk levels are not permitted. As a result, many transitions, including those, which might be functionally desirable, may be potentially excluded between states, which are located in sparsely populated areas of risk graphs. This is an inadequacy, which may be attributed to factors such as incomplete hazard analysis, the lack of information about relative risk levels of different states of the system, etc. In order to extend the permitted transition space in such circumstances and to enhance the risk ordering relation, this paper introduces the concept of risk band. Risk bands enable an unambiguous interpretation of the relevant risk level of states, thus allowing a well understood enhancement of risk graphs and an extension of the concept of safe non-determinism introduced in [2]. An example drawn from the nuclear industry demonstrates the application of Safecharts.