475 research outputs found
A Decidable Timeout based Extension of Propositional Linear Temporal Logic
We develop a timeout based extension of propositional linear temporal logic
(which we call TLTL) to specify timing properties of timeout based models of
real time systems. TLTL formulas explicitly refer to a running global clock
together with static timing variables as well as a dynamic variable abstracting
the timeout behavior. We extend LTL with the capability to express timeout
constraints. From the expressiveness view point, TLTL is not comparable with
important known clock based real-time logics including TPTL, XCTL, and MTL,
i.e., TLTL can specify certain properties, which cannot be specified in these
logics (also vice-versa). We define a corresponding timeout tableau for
satisfiability checking of the TLTL formulas. Also a model checking algorithm
over timeout Kripke structure is presented. Further we prove that the validity
checking for such an extended logic remains PSPACE-complete even in the
presence of timeout constraints and infinite state models. Under discrete time
semantics, with bounded timeout increments, the model-checking problem that if
a TLTL-formula holds in a timeout Kripke structure is also PSPACE complete. We
further prove that when TLTL is interpreted over discrete time, it can be
embedded in the monadic second order logic with time, and when TLTL is
interpreted over dense time without the condition of non-zenoness, the
resulting logic becomes -complete
LTL Parameter Synthesis of Parametric Timed Automata
The parameter synthesis problem for parametric timed automata is undecidable
in general even for very simple reachability properties. In this paper we
introduce restrictions on parameter valuations under which the parameter
synthesis problem is decidable for LTL properties. The investigated bounded
integer parameter synthesis problem could be solved using an explicit
enumeration of all possible parameter valuations. We propose an alternative
symbolic zone-based method for this problem which results in a faster
computation. Our technique extends the ideas of the automata-based approach to
LTL model checking of timed automata. To justify the usefulness of our
approach, we provide experimental evaluation and compare our method with
explicit enumeration technique.Comment: 23 pages, extended versio
PKind: A parallel k-induction based model checker
PKind is a novel parallel k-induction-based model checker of invariant
properties for finite- or infinite-state Lustre programs. Its architecture,
which is strictly message-based, is designed to minimize synchronization delays
and easily accommodate the incorporation of incremental invariant generators to
enhance basic k-induction. We describe PKind's functionality and main features,
and present experimental evidence that PKind significantly speeds up the
verification of safety properties and, due to incremental invariant generation,
also considerably increases the number of provable ones.Comment: In Proceedings PDMC 2011, arXiv:1111.006
How bit-vector logic can help improve the verification of LTL specifications over infinite domains
Propositional Linear Temporal Logic (LTL) is well-suited for describing properties of timed systems in which data belong to finite domains. However, when one needs to capture infinite domains, as is typically the case in software systems, extensions of LTL are better suited to be used as specification languages. Constraint LTL (CLTL) and its variant CLTL-over-clocks (CLTLoc) are examples of such extensions; both logics are decidable, and so-called bounded decision procedures based on Satisfiability Modulo Theories (SMT) solving techniques have been implemented for them. In this paper we adapt a previously-introduced bounded decision procedure for LTL based on Bit-Vector Logic to deal with the infinite domains that are typical of CLTL and CLTLoc. We report on a thorough experimental comparison, which was carried out between the existing tool and the new, Bit-Vector Logic-based one, and we show how the latter outperforms the former in the vast majority of cases
Fluid Model Checking
In this paper we investigate a potential use of fluid approximation
techniques in the context of stochastic model checking of CSL formulae. We
focus on properties describing the behaviour of a single agent in a (large)
population of agents, exploiting a limit result known also as fast simulation.
In particular, we will approximate the behaviour of a single agent with a
time-inhomogeneous CTMC which depends on the environment and on the other
agents only through the solution of the fluid differential equation. We will
prove the asymptotic correctness of our approach in terms of satisfiability of
CSL formulae and of reachability probabilities. We will also present a
procedure to model check time-inhomogeneous CTMC against CSL formulae
Utilization of timed automata as a verification tool for real-time security protocols
Thesis (Master)--Izmir Institute of Technology, Computer Engineering, Izmir, 2010Includes bibliographical references (leaves: 85-92)Text in English; Abstract: Turkish and Englishxi, 92 leavesTimed Automata is an extension to the automata-theoretic approach to the modeling of real time systems that introduces time into the classical automata. Since it has been first proposed by Alur and Dill in the early nineties, it has become an important research area and been widely studied in both the context of formal languages and modeling and verification of real time systems. Timed automata use dense time modeling, allowing efficient model checking of time-sensitive systems whose correct functioning depend on the timing properties. One of these application areas is the verification of security protocols. This thesis aims to study the timed automata model and utilize it as a verification tool for security protocols. As a case study, the Neuman-Stubblebine Repeated Authentication Protocol is modeled and verified employing the time-sensitive properties in the model. The flaws of the protocol are analyzed and it is commented on the benefits and challenges of the model
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