A Logical Characterization of Timed (non-)Regular Languages

Bersani, Marcello M.; Rossi, Matteo; Pietro, Pierluigi San

doi:10.1007/978-3-662-44522-8_7

Cited by 7 publications

(7 citation statements)

References 22 publications

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“…In fact, modeling real‐time executions of the server, where the relation between the computation delay and server load and the temporal relation among events matter, required a model that is affected by a combinatorial blow‐up. This drawback is unavoidable in the current setting and characterizes also the approaches based on timed automata that can be considered as an alternative to CLTLoc, being equivalent to CLTLoc . In addition, their inherent operational nature is not suitable to model logical constraints on quantitative measures, such as the servers load, the incompatibilities, and the utility function, resulting in an elaborated representation which, on the other hand, is very natural in a logical language.…”

Section: Discussionmentioning

confidence: 99%

Online verification in cyber‐physical systems: Practical bounds for meaningful temporal costs

Bersani

García-Valls

2017

J Software Evolu Process

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Cyber‐physical systems (CPS) are highly dynamic and large scale systems integrated with the physical environment that they monitor and actuate on. CPS have to adapt online to the changing nature of the physical environment; this may require the online modification of their system model, but any change should preserve correct operation. Correctness by construction relies on using formal tools, which suffer from a considerable computational overhead. As the current system model of a CPS may adapt to the environment, the new system model must be verified before its execution to ensure that the properties are preserved. However, CPS development has mainly concentrated on the design‐time aspects, existing only few contributions that address their online adaptation. We research on the pros and cons of formal tools to support dynamic changes at runtime. We formalize the semantics of the adaptation logic of an autonomic manager (OLIVE) that performs online verification for a specific application, a dynamic virtualized server system. We explore the use of formal tools based on CLTLoc to express functional and nonfunctional properties of the system. We provide empirical results showing the temporal costs of our approach.

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Section: Discussionmentioning

confidence: 99%

Online verification in cyber‐physical systems: Practical bounds for meaningful temporal costs

Bersani

García-Valls

2017

J Software Evolu Process

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“…In fact, modeling real-time executions of the server, where the relation between the computation delay and server load and the temporal relation among events matter, required a model that is affected by a combinatorial blow-up. This drawback is unavoidable in the current setting and characterizes also the approaches based on Timed automata which can be considered as an alternative to CLTLoc, being equivalent to CLTLoc [6]. In addition, their inherent operational nature is not suitable to model logical constraints on quantitative measures, like the servers load, the incompatibilities and the utility function, resulting into an elaborated representation which, on the other hand, is very natural in a logical language.…”

Section: Discussionmentioning

confidence: 99%

The Cost of Formal Verification in Adaptive CPS. An Example of a Virtualized Server Node

Bersani

García-Valls

2016

2016 IEEE 17th International Symposium on High Assurance Systems Engineering (HASE)

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Cyber-physical systems (CPS) are large scale systems highly integrated with the physical environment. Given the changing nature of physical environments, CPS must be able to adapt on-line to new situations while preserving their correct operation. Correctness by construction relies on using formal tools, which suffer from a considerable computational overhead especially if executed on-line. As the current system model of a CPS may change to adapt to the environment, the new system model has to be verified at run-time prior to its execution to ensure that the system properties are preserved. CPS development has mainly concentrated on the design-time aspects, existing only few contributions that support on-line adaptation.We undertake a practical exercise to research on the pros and cons of formal tools to support dynamic changes at run-time. We formalize the semantics of the adaptation logic of an autonomic manager (OLIVE) that performs on-line verification for a specific application, i.e., a dynamic virtualized server system. We explore the realization of the autonomic manager using formal tools based on CLTLoc to express functional and non-functional properties of the managed system. The on-line verification manager services requests from mobile clients that might require a change in both the running software components and server services. To establish if the adaptation preserves the temporal constraints provided in the specification, i.e., to decide whether a new client request can be serviced in the modified system, the online verification manager employs CLTLoc satisfiability checking. In this scenario, we then provide empirical results showing the temporal costs of our approach.

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“…CLTLoc (CLTL-over-clocks) is a variant of CLTL where the clock variables are the only arithmetic variables that are considered in the atomic constraints. It has been proven in [11] that CLTLoc is equivalent to timed automata [16]. Moreover, it can be polynomially reduced to decidable Satisfiability Modulo Theories which are solvable by many SMT solvers such as Z3 10 .…”

Section: A Mitl Satisfiabilitymentioning

confidence: 99%

Formal Requirement Debugging for Testing and Verification of Cyber-Physical Systems

Dokhanchi

Hoxha

Fainekos

2017

ACM Trans. Embed. Comput. Syst.

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A framework for the elicitation and debugging of formal specifications for Cyber-Physical Systems is presented. The elicitation of specifications is handled through a graphical interface. Two debugging algorithms are presented. The first checks for erroneous or incomplete temporal logic specifications without considering the system. The second can be utilized for the analysis of reactive requirements with respect to system test traces. The specification debugging framework is applied on a number of formal specifications collected through a user study. The user study establishes that requirement errors are common and that the debugging framework can resolve many insidious specification errors 1 . evaluates to true no matter what the system behavior is and, thus, the requirement ϕ is invalid. This is because, if at some time t between 0 and 30 seconds the predicate (v > 100) is false, then the implication (⇒) will trivially evaluate to true at time t and, thus, ϕ will evaluate to true as well. On the other hand, if the predicate (v > 100) is true for all time between 0 and 30 seconds, then the subformula 2 [0,20] (v > 100) will be true at all time between 0 and 10 seconds. This means that the subformula (v > 100) ⇒ 2 [0,20] (v > 100) is true at all time between 0 and 10 seconds. Thus, again, ϕ evaluates to true, which means that ϕ is a tautology.This implies that specification issues are not necessarily artifacts of the graphical user interface and that they can happen even for users who are familiar with temporal logics. Hence, specification elicitation can potentially become an issue as formal and semi-formal testing and verification methods and tools are being adopted by industry. This is because specification elicitation can be performed by untrained users. Therefore, effort can be wasted in checking incorrect requirements, or even worse, the system can pass the incorrect requirements. Clearly, this can lead to a false sense of system correctness, which leads us to the second question: What can be done in an automated way to prevent specification errors in CPS?In this work, we have developed a specification debugging framework to assist in the elicitation of formal requirements. The specification debugging algorithm identifies some of the logical issues in the specifications, but not all of them. Namely, it performs the following: 1) Validity detection: the specification is unsatisfiable or a tautology. 2) Redundancy detection: the formula has redundant conjuncts.3) Vacuity detection: some subformulas do not affect the satisfiability of the formula.Redundancy and vacuity issues usually indicate some misunderstanding in the requirements. As a result, a wide class of specification errors in the elicitation process can be corrected before any test and verification process is initiated. However, some specification issues cannot be detected unless we consider the system, and test the system behaviors with respect to the specification. We provide algorithms to detect specification vacuity with respect to system trace...

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A Logical Characterization of Timed (non-)Regular Languages

Cited by 7 publications

References 22 publications

Online verification in cyber‐physical systems: Practical bounds for meaningful temporal costs

Online verification in cyber‐physical systems: Practical bounds for meaningful temporal costs

The Cost of Formal Verification in Adaptive CPS. An Example of a Virtualized Server Node

Formal Requirement Debugging for Testing and Verification of Cyber-Physical Systems

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