ing WS1S Systems to Verify Parameterized Networks . . . . . . . . . . . . 188 Kai Baukus, Saddek Bensalem, Yassine Lakhnech and Karsten Stahl FMona: A Tool for Expressing Validation Techniques over Infinite State Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 J.-P. Bodeveix and M. Filali Transitive Closures of Regular Relations for Verifying Infinite-State Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 Bengt Jonsson and Marcus Nilsson Diagnostic and Test Generation Using Static Analysis to Improve Automatic Test Generation . . . . . . . . . . . . . 235 Marius Bozga, Jean-Claude Fernandez and Lucian Ghirvu Efficient Diagnostic Generation for Boolean Equation Systems . . . . . . . . . . . . 251 Radu Mateescu Efficient Model-Checking Compositional State Space Generation with Partial Order Reductions for Asynchronous Communicating Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 Jean-Pierre Krimm and Laurent Mounier Checking for CFFD-Preorder with Tester Processes . . . . . . . . . . . . . . . . . . . . . . . 283 Juhana Helovuo and Antti Valmari Fair Bisimulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 Thomas A. Henzinger and Sriram K. Rajamani Integrating Low Level Symmetries into Reachability Analysis . . . . . . . . . . . . . 315 Karsten Schmidt Model-Checking Tools Model Checking Support for the ASM High-Level Language . . . . . . . . . . . . . . 331 Giuseppe Del Castillo and Kirsten Winter Table of

Tools and Algorithms for the Construction and Analysis of Systems. Proc. TACAS 2009

The tool Imitator implements the Inverse Method (IM) for Timed Automata (TAs). Given a TA \(\mathcal{A}\) and a tuple π 0 of reference valuations for timings, IM synthesizes a constraint around π 0 where \(\mathcal{A}\) behaves in the same discrete manner. This provides us with a quantitative measure of robustness of the behavior of \(\mathcal{A}\) around π 0. The new version Imitator 2.5 integrates the new features of stopwatches (in addition to standard clocks) and updates (in addition to standard clock resets), as well as powerful algorithmic improvements for state space reduction. These new features make the tool well-suited to analyze the robustness of solutions in several classes of preemptive scheduling problems.

IMITATOR 2.5: A Tool for Analyzing Robustness in Scheduling Problems

Advanced technologies have changed the nature of business processes in the form of services. In coordinating services to achieve a particular objective, service workflow is used to control service composition, execution sequences as well as path selection. Since existing mechanisms are insufficient for addressing the diversity and dynamicity of the requirements in a large-scale distributed environment, developing formal requirements specification is necessary. In this paper, we propose a Service Workflow Specification language, called SWSpec, which allows arbitrary services in a workflow to formally and uniformly impose their requirements. As such, the solution will provide a formal way to regulate and control workflows as well as enrich the proliferation of service provisions and consumptions in opened environments.

SWSpec: The Requirements Specification Language in Service Workflow Environments

https://www-dssz.informatik.tu-cottbus.de/publications/materials/silva-2013-50years-of-pn.pdf

Half a century after Carl Adam Petri’s Ph.D. thesis: A perspective on the field

We provide a subclass of parametric timed automata (PTA) that we can actually and efficiently analyze, and we argue that it retains most of the practical usefulness of PTA for the modeling of real-time systems. The currently most useful known subclass of PTA, L/U automata, has a strong syntactical restriction for practical purposes, and we show that the associated theoretical results are mixed. We therefore advocate for a different restriction scheme: since in classical timed automata, real-valued clocks are always compared to integers for all practical purposes, we also search for parameter values as bounded integers. We show that the problem of the existence of parameter values such that some TCTL property is satisfied is PSPACE-complete. In such a setting, we can of course synthesize all the values of parameters and we give symbolic algorithms, for reachability and unavoidability properties, to do it efficiently, i.e., without an explicit enumeration. This also has the practical advantage of giving the result as symbolic constraints between the parameters. We finally report on a few experimental results to illustrate the practical usefulness of our approach.

/pdf/integer-parameter-synthesis-for-real-time-systems-4td9xzznwc.pdf

Integer Parameter Synthesis for Real-Time Systems

Last time we reported on Romeo, analyses with this tool were mostly based on translations to other tools. This new version provides an integrated TCTL model-checker and has gained in expressivity with the addition of parameters. Although there exists other tools to compute the state-space of stopwatch models, Romeo is the first one that performs TCTL model-checking on stopwatch models. Moreover, it is the first tool that performs TCTL model-checking on timed parametric models. Indeed, Romeo now features an efficient model-checking of time Petri nets using the Uppaal DBM Library, the model-checking of stopwatch Petri nets and parametric stopwatch Petri nets using the Parma Polyhedra Library and a graphical editor and simulator of these models. Furthermore, its audience has increased leading to several industrial contracts. This paper reports on these recent developments of Romeo.

http://people.rennes.inria.fr/Louis-Marie.Traonouez/publications/tacas09.pdf

Romeo: A Parametric Model-Checker for Petri Nets with Stopwatches

Safety analysis in systems engineering (SE) processes, as usually implemented, rarely relies on formal methods such as model checking since such techniques, however powerful and mature, are deemed too complex for efficient use. This paper thus aims at improving the verification practice in SE design: considering the widely-used model of enhanced function flow block diagrams (EFFBDs), it formally establishes its syntax and behavioral semantics. It also proposes a structural translation of EFFBDs to transition time Petri nets ( TPNs); this translation is then proved to preserve the behavioral semantics (i.e., timed bisimilarity). After proving results on the boundedness of the resulting TPNs, it was possible to extend a number of fundamental properties (such as the decidability of liveness, state-access, etc.) from bounded TPNs to so-called bounded EFFBDs. Finally, these results led to both implementing and integrating a formal verification tool within a development platform for system design for defense applications and in which the underlying complexity is totally concealed from the end-user.

https://hal.archives-ouvertes.fr/hal-00489291/document

Formal Methods for Systems Engineering Behavior Models

Verification is a key process in the dependability engineering of complex systems. As we have shown in earlier works, formal verification techniques such as model checking can be efficiently used in a Systems Engineering (SE) context, despite their inherent complexity. Considering the widely used Enhanced Function Flow Block Diagrams (EFFBDs), we have indeed developed a formal simulation and verification tool for these functional behavior models. Moreover, great care has been taken to conceal the processing complexity from the tool end-user.



In this paper, we present our latest developments as well as an extension of both method and tool to the case of dysfunctional models, to take into account failures affecting the model elements. By addressing both fault removal and fault forecasting problems with formal methods, we thus hope to improve the dependability analysis practice in SE.

5.4.1 Simulation and Verification of [Dys]functional Behavior Models: Model Checking for SE

In order to model resource-consumption or allocation problems in concurrent real-time systems, we propose an extension of time Petri nets (TPN) with a linear cost function and investigate the minimum/infimum cost reachability problem. We build on the good properties of the state class symbolic abstraction, which is coarse and requires no approximation (or k-extrapolation) to ensure finiteness, and extend this abstraction to symbolically compute the cost of a given sequence of transitions. We show how this can be done, both by using general convex polyhedra, but also using the more efficient Difference Bound Matrix (DBM) data structure. Both techniques can then be used to obtain a symbolic algorithm for minimum cost reachability in bounded time Petri nets with possibly negative costs (provided there are no negative cost cycles). We prove that this algorithm terminates in both cases by proving that it explores only a finite number of extended state classes for bounded TPN, without having to resort to a bounded clock hypothesis, or to an extra approximation/extrapolation operator. All this is implemented in our tool Romeo and we illustrate the usefulness of these results in a case study.

/pdf/optimal-reachability-in-cost-time-petri-nets-2q1j388lpp.pdf

Optimal Reachability in Cost Time Petri Nets

Although the eFFBD formalism dates back to the 1990s (or even, in a simplified
form, the 1950s), it seems that it is still not as much used by the Systems Engineering community as it could. Indeed, eFFBD is a modeling language focusing on functional paradigm
i.e. allowing functional and behavioral modeling and reasoning about a system. Currently, it
is often confronted or compared to other languages such as SysML for activity modeling (activity diagrams) based on object paradigm. This paper aims to demonstrate the interest and
the potential advantages for systems designers, like most of the discipline-oriented designers to dispose of an enriched (conceptually and semantically) eFFBD modeling language called here xFFBD. This has to be a credible framework for modeling, communicating and reasoning about complex systems. After shortly recalling the history, the key concepts and capabilities of eFFBD, this paper compares eFFBD with other formalisms considered here as relevant for the study, Petri nets and SysML. Several leads are then identified and discussed in order to improve the eFFBD language and to provide a first draft version of xFFBD specification.

/pdf/1-6-1-xffbd-towards-a-formal-yet-functional-modeling-16aeozytem.pdf

Charlotte Seidner

Papers

Romeo: A Parametric Model-Checker for Petri Nets with Stopwatches

Formal Methods for Systems Engineering Behavior Models

5.4.1 Simulation and Verification of [Dys]functional Behavior Models: Model Checking for SE

Optimal Reachability in Cost Time Petri Nets

1.6.1 xFFBD: towards a formal yet functional modeling language for system designers