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Model checking petri nets with MSVL
Abstract
This paper presents three translations from Petri nets to Modeling, Simulation and Verification Language (MSVL) programs. Each translation is directed by one of the three semantics of Petri nets, namely interleaving, concurrency and max-concurrency. Further, for each translation, an equivalence relation between Petri nets and generated MSVL programs is proved. As a result, the supporting tool MSV for MSVL can be used to verify the properties of Petri nets. Case studies are given to show how to do so with MSV under each semantics.
... The formal model of an RDECS can be described by one of the several existing formalisms: Petri nets, automata, net condition events systems (NCESs), timed NCESs, or reconfigurable timed net condition event systems (R-TNCESs) [20]. In the last decade, Petri nets have found extensive applications in various DES tasks, including modeling and analysis [21]- [23], deadlock resolution [24], synthesis of liveness-enforcing controllers for flexible manufacturing systems [25], [26], scheduling [27], [28] and its optimization with metaheuristics methods [29], supervisory control [30], [31], and observation structures [32]. Also, Petri nets are used in fault diagnosis [33], state-based opacity verification [34], consistency comparison for workflow nets [35], detecting problems for programmable logic controllers [36], stability analysis of systems with fuzziness [37], and lowpower reconfiguration of real-time systems [38], as well as in knowledge representation and reasoning of rule-based expert systems [39]. ...
... For abbreviation, we write p i j where the first index in each element matches the subscript of the original set. Then, 23 }. An R-TNCES is a structure composed of multi-TNCES superposed that represents several configurations that are managed by transformation rules. ...
This article deals with improved formal verification of reconfigurable discrete-event systems (DESs) modeled by reconfigurable timed net condition event systems (R-TNCESs). An R-TNCES consists of a set of timed net condition event systems, each of which represents a particular behavior of a DES, and a reconfiguration scenario is a switching mode from a timed net condition event system to another. However, the verification with the classical computation tree logic (CTL) as well as the related extensions increases the number of properties for complete verification of a complex R-TNCES. We propose reconfigurable CTL as a new extension of CTL to reduce such a number. New connectors of reconfigurable CTL are proposed, with their formal syntax and semantics, and a set of new algorithms is proposed to control the complexity of model checking. We use a benchmark production system for the performance evaluation of the proposed approach. Reduction in the number of properties to be checked is shown, and consequently, the related validation time is reduced.
... ere are alternative and complementary ways for verifying properties of concurrent systems, including those described in terms of Petri nets. Simulation seems to be the most used technique reported in the literature for performance analysis, generally on a timed/stochastic Petri net model, while model-checking is the most used technique for property checking [2,4,11,18,30,35]. However, besides possibly facing state explosion, model checkers do not produce explicit certi cates when a property holds. ...
Petri Nets are a widely used formalism to deal with concurrent systems. Dynamic Logics (DLs) are a family of modal logics where each modality corresponds to a program. Petri-PDL is a logical language that combines these two approaches: it is a dynamic logic where programs are replaced by Petri Nets. In this work we present a clausal resolution-based calculus for Petri-PDL. Given a Petri-PDL formula, we show how to obtain its translation into a normal form to which a set of resolution-based inference rules are applied. We show that the resulting calculus is sound, complete, and terminating. Some examples of the application of the method are also given.
... The success of this method should give credit to the effective of software tool, such as Spin, SMV, CWB and so on. Petri net [6] and Promela [7] are the verification models which the modeling of present system often uses. The formalization foundation of Petri net is good. ...
... Petri nets and their extensions (e.g., for dealing with real time and stochastic systems) represent an excellent model for DESs and provide a wellestablished suite of tools for their formal verification [121,122]. Future works will also explore advanced operational models for large-scale collective adaptive systems, such as the work in [119]. ...
Advancements on microelectromechanical systems, embedded technologies, and wireless communications have recently enabled the evolution of conventional everyday things in enhanced entities, commonly defined Smart Objects (SOs). Their continuous and widespread diffusion, along with an increasing and pervasive connectivity, is enabling unforeseen interactions with conventional computing systems, places, animals and humans, thus fading the boundary between physical and digital worlds. The Internet of Things (IoT) term just refers to such futuristic scenario, namely a loosely coupled, decentralized and dynamic ecosystem in which billions (even trillions) of self-steering SOs are globally interconnected becoming active participants in business, logistics, information and social processes. Indeed, SOs are able to provide highly pervasive cyberphysical services to both humans and machines thanks to their communication, sensing, actuation, and embedded processing capabilities. Nowadays, the systemic revolution that can be led through the complete realization of the IoT vision is just at its dawn. As matter of facts, whereas new IoT devices and systems have been already developed, they often result in poorly interoperating "Intra-nets of things", mainly due to the heterogeneity featuring IoT building blocks and the lack of standards. Thus, the development of massive scaled (the total number of "things" is forecasted to reach 20.4 billion in 2020) and actually interoperable IoT systems is a challenging task, featured by several requirements and novel, even unsurveyed, issues. In this context, a multidisciplinary and systematic development approach is necessary, so to involve different fields of expertise for coping with the cyberphysical nature of IoT ecosystem. Henceforth, full-fledged IoT methodologies are gaining traction, aiming at systematically supporting all development phases, addressing mentioned issues, and reducing time-to-market, efforts and probability of failure. In such a scenario, this Thesis proposes an application domain-neutral, full-fledged agent-based development methodology able to support the main engineering phases of IoT ecosystems. The definition of such systematic apiproach resulted in ACOSO-Meth (Agent-based COoperating Smart Objects
Methodology), which is the major contribution of this thesis along with other interesting research efforts supporting (i.e., a multi-technology and multiprotocol smartphone-based IoT gateway) and extending (i.e., a full-fledged approach to the IoT services modeling according to their opportunistic properties) the main proposal. Finally, to provide validation and performance evaluation of the proposed ACOSO-Meth approach, four use cases (related to different application contexts such as a smart university campus, a smart digital library, a smart city and a smart workshop) have been developed. These research prototypes showed the effectiveness and efficiency of the proposed approach and improved their respective state-of-the-art.
... Our future work intend to focus on an integrated framework for supporting the formal verification, simulation and implementation of IoT services before their deployment [13]. Formal methods and verification tools, e.g., Petri nets [14,15], will be explored and applied. Additionally, we plan to investigate the application of aggregate computing techniques to foster the "collective adaptive" character of opportunistic IoT services [16]. ...
Services have a paramount importance for unfolding
the potential of the future Internet of Things (IoT), a dense, open,
cyberphysical ecosystem in which humans, conventional
computing systems and daily objects straightforwardly
interoperate. By summarizing our previous contributions in such
novel research context, this paper promotes our vision of
“Opportunistic IoT Services” and a full-fledged approach to their
modeling according to their opportunistic properties. Its
effectiveness and flexibility is illustrated by means of two case
studies, related to the Industrial IoT and Smart City scenarios
... Doing so, it is possible to model, verify and simulate IoT Services by taking into account relevant elements defining their ServiceProfile and Service Model (e.g., service/process input, output, preconditions, and effects), as well as important IoT Entity features (e.g., constraints, and preferences locations). Petri nets and their extensions (e.g., for dealing with real time and stochastic systems) represent an excellent model for DESs and provide a well-established suite of tools for their formal verification [15], [18]. Future works will also explore advanced Figure 4 Smart Object modeling and main features related to service provision (in red the extensions with respect to [17]) operational models for large-scale collective adaptive systems, such as the work in [16]. ...
Internet of Thing (IoT) is transforming our physical world into a giant information system, daily providing novel, advanced, cyberphysical services. Differently from conventional computing services (e.g., web-services, and ubiquitous services) that are usually loosely impacted by context-awareness, co-location or transience, Internet of Things (IoT) services require to actually consider the overall spatio-temporal context of the heterogeneous entities involved in the service provisioning. This paper proposes a novel and full-fledged approach to IoT service modeling, aiming to fully support IoT service development according to opportunistic properties.
Propositional Projection Temporal Logic (PPTL) has been widely used in formal verification, and its expressiveness is suitable for the description of security requirements. However, the expression and application of temporal logic formulas rely on a strong mathematical background, which is difficult for non-domain experts, thus bridging the chasm between natural language descriptions and formal languages is urgently needed. This paper proposes an innovative architecture for neural machine automatic translation named NL2PPTL, which transforms natural language into PPTL specification via utilizing data preprocessing, encoder-decoder network and stack sequentially. To evaluate the performance of our method, the experimental verification is realized on real datasets. The experiment conducted shows that our method has effectiveness on temporal logic specification generation.KeywordsNeural machine translationPropositional projection temporal logicFormal specificationFormal verification
A formal specification is a formal description of system requirements, which is a necessity for formal verification. Due to various reasons, some systems lack of formal specifications. Compared with CTL and LTL, Propositional Projection Temporal Logic (PPTL) has a full regular expressive power. Accordingly, a pattern-library-based PPTL specification mining tool PPTLMiner [1] is able to dig out a better expression of system specification. However, there's still some room for improvement in PPTLMiner, such as deep recursion, high time complexity and space complexity, which limit the use of PPTLMiner in practical applications. Therefore, in this paper, a new PPTL specification mining approach based on Labeled Normal Form Graph(LNFG) is proposed and a supporting tool PPTLMiner+ is also developed. Finally, a specification mining example using PPTLMiner+ is given to illustrate the effectiveness and practicality of the new approach. In this example, a typical algorithm in Swarm Intelligence-Bee Colony Algorithm is selected as a target program, and the working order of EmployedBees, OnlookerBees and ScoutBees is obtained using PPTLMiner+. Further, PPTLMiner+ is compared with PPTLMiner as well as the classical linear specification mining tool Texada [2], [3] in terms of time and memory to illustrate the effectiveness and practicability of the proposed method.
There are many cases in which our understanding of a system may be limited due to its complexity or lack of access into the entire system, leaving us with only partial system knowledge. This paper proposes a novel systematic active-learning method for realizing a partially-known Discrete Event System (DES). The proposed technique takes the available information about the system into account by tabularly capturing the known data from the system, and then, discovers the unknown part of the system via an active-learning procedure. For this purpose, a series of tables will be constructed to first infer the information about the system from the available data, and if unavailable, the developed algorithm collects the information through basic queries made to an oracle. It is proven that the developed technique returns a language-equivalent finite-state automaton model for the system under identification after a finite number of iterations. A real-world illustrative example is provided to explain the details of the proposed method.
The development of types is an important but challenging issue in temporal logic programming. In this paper, we investigate how to formalize and implement types in the temporal logic programming language MSVL, which is an executable subset of projection temporal logic (PTL). Specifically, we extendMSVL with a few groups of types including basic data types, pointer types and struct types. On each type, we specify the domain of values and define some standard operations in terms of logic functions and predicates. Then, it is feasible to formalize statements of type declaration of program variables and statements of struct definitions as logic formulas. As the implementation of the theory, we extend theMSV toolkit with the support of modeling, simulation and verification of typedMSVL programs. Applications to the construction of AVL tree and ordered list show the practicality of the language. © 2017 Higher Education Press and Springer-Verlag Berlin Heidelberg
This paper presents an ordinary Petri net (PN)-based approach to the modeling and race-detection problems of programs for programmable logic controllers (PLCs). First, a PLC program is formalized by a graph where nodes represent contacts and coils. Second, an algorithm is proposed to translate this graph into an ordinary PN. Third, a method is presented to detect whether there exists a race in a program by using a reachability graph technique, to locate a race by introducing the race path, and to correct a race by analyzing the subnet that contains it. An example is utilized to illustrate the theoretic results.
Petri nets are a successful formal method for the modeling and verification of asynchronous, concurrent and distributed systems. Reachability analysis can provide important information about the behavior of the model. However, reachability analysis is a computationally hard problem, especially when the state space is infinite. Abstraction-based techniques are often applied to overcome complexity. In this paper we analyze an algorithm, which uses counterexample guided abstraction refinement. This algorithm proved its efficiency on the model checking contest. We examine the algorithm from a theoretical and practical point of view. On the theoretical side, we show that the algorithm cannot decide reachability for relatively simple instances. We propose a new iteration strategy to explore the invariant space, which extends the set of decidable problems. We also give proofs on the theoretical limits of our approach. On the practical side, we examine different search strategies and we present our new, complex strategy with superior performance compared to traditional strategies. Measurements show that our new contributions perform well for traditional benchmark models as well.
As a powerful analysis tool of Petri nets, reachability trees are fundamental for systematically investigating many characteristics such as boundedness, liveness and reversibility. This work proposes a method to generate a reachability tree, called !RT for short, for a class of unbounded generalized nets called ! independent nets based on new modified reachability trees (NMRTs). !RT can effectively decrease the number of nodes by removing duplicate and !-duplicate nodes in the tree, and verify properties such as reachability, liveness and deadlocks. Two examples are provided to show its superiority over NMRTs in terms of tree size.
This paper proposes a general approach, called a think-globally-act-locally method with weighted arcs (TGALW), which can be used to compute a liveness-enforcing supervisor (LES) for the Petri net (PN) model of a flexible manufacturing system (FMS) prone to deadlocks. Compared with siphon-based deadlock prevention policies that are usually rather conservative, the method is especially effective for generalized PN classes such as S4R and S4PR and also leads to optimal or near optimal LESs while maintaining the necessary computations simple. An original PNM is first transformed into a net that is behaviorally equivalent to it. A global sink/source place (GP) is used temporarily in the design steps and is finally removed when the liveness of the system is achieved. At each iteration step, bad markings are identified and then controlled by monitors through an established place-invariant based method. A condition of the optimal controllability of a bad marking is proposed, i.e., if all bad markings are optimally controlled at each iteration step, the TGALW method can find an optimal LES. Redundancy of monitors is checked. Typical examples existing in the literature are used to demonstrate applicability and the effectiveness of the proposed method.
The most important challenge in region based abstraction method as one of the approaches to compute the state space of Time Petri Net (TPN) models for model checking is that the method results in huge number of regions causing state explosion problem. Hence, region based abstraction method is not appropriate to be used in developing practical tools. To overcome this shortcoming, this paper applies a modification to the basic region abstraction method to be specially used for computing the state space of TPN models, so that, the number of regions becomes less than the situations in which the existing methods are applied. Therefore, the proposed approach can be used in practical applications and tools since it does not show state explosion. The proposed approach is based on the special features of TPN that enables us to construct very suitable and small region graph which preserves time properties of TPN. To achieve our goal, we extend TPN-TCTL as a timed extension of CTL for specifying a subset of properties on TPN models. Afterward, for model checking TPN-TCTL properties on TPN models, by translating TPN-TCTL to the equivalent CTL, CTL model checking is used on TPN models. Finally, we compare our proposed method with the previously proposed region based abstraction methods for TPN considering the number of regions resulting from the methods.
Liveness is a basic property of a system and the liveness issue of unbounded Petri nets remains one of the most difficult problems in this field. This work proposes a novel method to decide the liveness of a class of unbounded generalized Petri nets called ω-independent unbounded nets, breaking the existing limits to one-place-unbounded nets. An algorithm to construct a macro liveness graph (MLG) is developed and a critical condition based on MLG deciding the liveness of ω-independent unbounded nets is proposed. Examples are provided to demonstrate its effectiveness.
The paper deals with the problem of translation of reachability graphs for place-transition and coloured Petri nets into the NuSMV language. The trans-lation algorithms presented in the paper have been implemented as a part of the PetriNet2NuSMV tool so the translation is made automatically. The PetriNet2Nu-SMV tool works with reachability graphs generated by the TINA and CPN Tools software. Thus, it provides the possibility of formal verification of Petri nets de-signed with these environments using model checking techniques and a main-stream model checker for LTL and CTL temporal logics.
GreatSPN is a tool for the definition and solution of generalized stochastic Petri nets (GSPN). This paper presents the model checking features that have been recently introduced in GreatSPN. Through a new (Java-based) graphical interface for the GSPN model definition, the user can now access model checking of three different logics: the classical branching temporal logic CTL, and two stochastic logics, CSL and its superset CSL TA . This allows to integrate easily classical and probabilistic verification. A distinctive feature of the CTL model checker is the ability of generating counterexamples and witnesses. The CTL model checker employs symbolic data structures (decision diagrams) implemented in the Meddly library [6], developed Iowa State University, while the CSL TA model checker uses advanced solution methods, recently published, for Markov renewal processes.
Model checking is an important part of the theoretical informatics. It
enables the verification of a model with a set of properties such as liveness,
deadlock or safety. Furthermore, Petri nets are well known and can be used for
a model checking process. Wider, a reconfigurable Petri net is based on a pure
Petri net with a set of rules. These rules can be used dynamically to change
the net itself. One missing part of these nets is the possibility to verify a
given net with a set of rules and properties. This paper attempts to fill this
gap. It presents a transformation approach which is based on Maude's equation-
and rewrite logic as well as the LTLR model checker.
Autoimmune diseases are characterized by loss of self-tolerance and the development of autoantibodies to self-antigens that result in chronic inflammation of tissues and organs. The etiology of autoimmune diseases is complex and involves a combination of genetic and environmental factors. Since most autoimmune diseases demonstrate familial inheritance, there has been great interest in identifying the genetic factors that influence disease predisposition. The hope is that this knowledge will lead to improvements in our ability to predict, treat and cure autoimmune diseases for future generations. To that end, genome-wide association studies (GWAS) have been successful in identifying the genomic regions that influence susceptibility to autoimmune diseases. For autoimmune diseases alone, ~700 genomic regions have been identified by GWAS in 183 studies. However, in the wake of GWAS, very few of the actual causal variants have been identified and biologically defined, in part because the causal variant alleles responsible for disease predisposition are dispersed among a much larger number of non-causal variant alleles in highly correlated haplotypes. This characteristic of the human genome, known as linkage disequilibrium (LD), neutralizes the power of genetic association methods to distinguish causal from non-causal variants. Therefore, to be successful in isolating and functionally characterizing the causal variants responsible for predisposition to disease, a multidisciplinary approach must be considered. In this review, we will discuss the approaches currently in use to prioritize candidate causal variants and describe recent advances in comparative and functional genomics that enable systematic annotation, functional testing, and characterization of autoimmune disease-associated variants. © 2014 American College of Rheumatology.
This paper develops a novel deadlock prevention policy for a class of generalised Petri nets, namely S4PR that can well model flexible manufacturing systems FMS. The analysis of generalised Petri nets leads us to characterise deadlock situations in terms of insufficiently marked siphons. The theory of elementary siphons guides our efforts towards the development of structurally simple liveness-enforcing supervisors. Therefore, insufficiently marked siphons can be classified into elementary ones and dependent ones. The controllability of a dependent siphon can be ensured by properly supervising its elementary ones. In order to find a compact and proper set of elementary siphons for S4PR, the concept of augmented siphons is proposed. Then, the concept of max′-controlled siphons is employed, which can relax the siphon controllability condition. By explicitly controlling elementary siphons via adding monitors, a liveness-enforcing controlled system can be found. In addition, the liveness-enforcing supervisor with more permissive behaviour is obtained through the rearrangement of the output arcs of the monitors. Finally, an FMS case study is utilised to demonstrate the proposed method.
We give an efficient procedure for verifying that a finite-state concurrent system meets a specification expressed in a (propositional, branching-time) temporal logic. Our algorithm has complexity linear in both the size of the specification and the size of the global state graph for the concurrent system. We also show how this approach can be adapted to handle fairness. We argue that our technique can provide a practical alternative to manual proof construction or use of a mechanical theorem prover for verifying many finite-state concurrent systems. Experimental results show that state machines with several hundred states can be checked in a matter of seconds.
The complexity of satisfiability and determination of truth in a particular finite structure are considered for different propositional linear temporal logics. It is shown that these problems are NP-complete for the logic with F and are PSPACE-complete for the logics with F, X, with U, with U, S, X operators and for the extended logic with regular operators given by Wolper.
In this paper we present sequential as well as distributed algorithms for model checking computational tree logic over finite-state systems specified as Petri nets. The algorithms rely on an explicit representation of the systems state space but do not require the transition relation to be explicitly available; it is recomputed whenever required. This approach allows us to model check very large systems, with hundreds of millions of states, in a fast and efficient way. For the case studies addressed, the distributed algorithms scale very well, as they show efficiencies in the range of 60% to 95%, depending on the test cases and case studies at hand.
: We report on an implementation of the unfolding approach to model-checking LTL-X recently presented by the authors. Contrary to that work, we consider an state-based version of LTL-X, which is more used in practice. We improve on the checking algorithm; the new version allows to reuse code much more efficiently. We present results on a set of case studies. KEYWORDS: Net unfoldings, model checking, tableau systems, Petri nets, LTL
State-space explosion is a major obstacle in verification of time-critical distributed systems. An important factor with a negative influence on the tractability of the analysis is the size of constants that clocks are compared to. This problem is particularly accented in explicit state-space exploration techniques. We suggest an approximation method for reducing the size of constants present in the model. The proposed method is developed for Timed-Arc Petri Nets and creates an under-approximation or an over-approximation of the model behaviour. The verification of approximated Petri net models can be considerably faster but it does not in general guarantee conclusive answers. We implement the algorithms within the open-source model checker TAPAAL and demonstrate on a number of experiments that our approximation techniques often result in a significant speed-up of the verification.
Crowd simulations have become increasingly popular in films over the last decade, appearing in large crowd shots of many big name block-buster films. An important requirement for crowd simulations in films is that they should be directable both at a high and low level. As agent-based techniques allow for low-level directability and more believable crowds, they are typically used in this field. However, due to the bottom-up nature of these techniques, to achieve high level directability, agent-level parameters must be adjusted until the desired crowd behavior emerges. As manually adjusting parameters is a time consuming and tedious process, this paper investigates a method for automating this, using Neuro-Evolution. To this end, the Conventional Neuro-Evolution (CNE), Covariance Matrix Adaptation Evolutionary Strategy (CMA-ES), Neuro-Evolution of Augmenting Topologies (NEAT), and Enforced Sub Populations (ESP) algorithms are compared across a variety of representative crowd simulation scenarios. Overall, it was found that CMA-ES generally performs the best across the selected simulations.
This paper presents an optimal solution to the robotic cell scheduling problem for robot movement controllers using timed Petri nets (TPNs). The suggested TPN approach is used to generate a mathematical transition model, based on a From/To transition matrix and the properties of the TPN, that considers all possible movements of robots between cell stations. The mathematical model thus obtained is solved to identify the optimal firing sequence of TPN transitions for the considered robotic cell problem to minimize the time elapsed before the firing of the last transition (the cycle time). Finally, the optimal sequence of transitions is used to generate robotic cell controllers and construct the final TPN model. A numerical example is used to demonstrate the proposed approach.
Petri nets have gained increasing usage and acceptance as a basic model of asynchronous concurrent systems since 1962. As a class of structural objects of Petri nets, siphons play a critical role in the analysis and control of systems modeled with Petri nets. This paper surveys the state-of-the-art siphon theory of Petri nets including basic concepts, computation of siphons, controllability conditions, and deadlock control policies based on siphons. Some open problems on siphons are discussed, such as the maximally permissive supervisor design problems based on siphons and the application of siphons to robust supervisory control. This survey is expected to serve as a reference source for the growing number of Petri net researchers and practitioners.
Whereas, for Petri nets, the traditional liveness property guarantees that each transition of a Petri net can always occur again, observable liveness requires that, from any reachable marking, each observable transition can be forced to fire by choosing appropriate controllable transitions; hence it is defined for Petri nets with distinguished observable and controllable transitions. We introduce observable liveness and show that this new notion generalizes traditional liveness in various ways. In particular, liveness of a 1-bounded Petri net implies observable liveness, provided the only conflicts that can appear are between controllable transitions. This assumption refers to applications where the uncontrollable part models a deterministic machine (or several deterministic machines), whereas the user of the machine is modeled by the controllable part and can behave arbitrarily.
Siphons are a kind of special structural objects in a Petri net, and plays a key role in synthesizing a live Petri net controller for flexible manufacturing systems. In order to obtain a small size Petri net controller, this paper introduces the concept of a controllable siphon basis. It then proves that a live Petri net controller can be established by adding a control place and related arcs to each strict minimal siphon (SMS) in a controllable siphon basis. The initial markings of control places are determined by an integer linear program. The number of control places in the obtained controllers is the same as the number of SMSs in the controllable siphon basis, while the latter is no more than that of the activity places in a Petri net model. An algorithm for constructing a controllable siphon basis is proposed, and a new deadlock prevention policy based on it is established. A few examples are provided to demonstrate the proposed concepts and policy and used to compare them with the state-of-the-art methods.
We propose a new, and to date the most general, framework for Petri net unfolding, which broadens its applicability, makes it easier to use, and increases its efficiency. In particular: (i) we propose a user-oriented view of the unfolding technique, which simply tells which information will be preserved in the final prefix and how to declare an event a cut-off in the algorithm, while hiding the technical parameters like the adequate order; (ii) the notion of the adequate order is generalised to a well-founded relation, and the requirement that it must refine ⊂ is replaced by a weaker one; and (iii) the order in which the unfolding algorithm selects the possible extensions of the prefix is entirely disentangled from the cut-off condition. We demonstrate the usefulness of the developed theory on some case studies.
Services offered in a commercial context are expected to deliver certain levels of quality, typically contracted in a service level agreement (SLA) between the service provider and consumer. To prevent monetary penalties and loss of reputation by violating SLAs, it is important that the service provider can accurately estimate the Quality of Service (QoS) of all its provided (composite) services. This paper proposes a technique for predicting whether the execution of a service composition will be compliant with service level objectives (SLOs). We make three main contributions. First, we propose a simulation technique based on Petri nets to generate composite time series using monitored QoS data of its elementary services. This techniques preserves time related information and takes mutual dependencies between participating services into account. Second, we propose a kernel-based quantile estimator with online adaptation of the constant offset to predict future QoS values. The kernel-based quantile estimator is a powerful non-linear black-box regressor that (i) solves a convex optimization problem, (ii) is robust, and (iii) is consistent to the Bayes risk under rather weak assumptions. The online adaption guarantees that under certain assumptions the number of times the predicted value is worse than the actual value converges to the quantile value specified in the SLO. Third, we introduce two performance indicators for comparing different QoS prediction algorithms. Our validation in the context of two case studies shows that the proposed algorithms outperform existing approaches by drastically reducing the violation frequency of the SLA while maximizing the usage of the candidate services.
In addition to the graphic-editing facilities, the software tool Tina proposes the construction of a number of representations for the behaviour of Petri nets or Time Petri nets. Various techniques are used to extract views of the behaviour of nets, preserving certain classes of properties of their state spaces. For Petri nets, these abstractions help prevent combinatorial explosion, relying on so-called partial order techniques such as covering steps and/or persistent sets. For Time Petri nets, which have, in general, infinite state spaces, they provide a finite symbolic representation of their behaviour in terms of state classes.
The reaction time of a controller is a fundamental matter in discrete event control systems. Petri nets are extensively used
in this field. The controller reads the inputs, executes the control Petri net and writes the output in a cyclic manner. The
reaction time of this controller depends on the Petri net structure, on the events sequence and on the algorithm that executes
the net. In this paper we present a performance evaluation of interpreted and centralized implementation techniques for ordinary
Petri nets. Four techniques have been analyzed: brute force, enabled transitions, static representing places and dynamic representing
places. The analysis has been carried out over a Petri net library composed of well know models which can be scaled using
a parameter. The analysis of the results shows that the performance of the algorithms depends on the Petri net behavior (concurrency
vs. effective conflicts).With the objective of minimizing the reaction time, we decided to design a Supervisor controller,
which we have called execution time controller (ETC). The aim of the ETC is to determine in real time which algorithm executes
the Petri net fastest and to change the execution algorithm when necessary. One possible application of the technique is the
minimization of execution time of the programmable logic controllers programs developed in sequential function chart (SFC).
KeywordsPetri nets–Algorithms–Discrete event systems–Programmable logic devices–Automation
This paper investigates the satisfiability of Propositional Projection Temporal Logic (PPTL) with infinite models. A decision
procedure for PPTL formulas is given. To this end, Normal Form (NF) and Labeled Normal Form Graph (LNFG) for PPTL formulas
are defined, and algorithms for transforming a formula to its normal form and constructing the LNFG for the given formula
are presented. Further, the finiteness of LNFGs is proved in details. Moreover, the decision procedure is extended to check
the satisfiability of the formulas of Propositional Interval Temporal Logic. In addition, examples are also given to illustrate
how the decision procedure works.
This paper proposes using Zero-Suppressed BDDs for the CTL symbolic model checking of Petri nets. Since the state spaces of Petri nets are often very sparse, it is expected that ZBDDs represent such sparse state spaces more efficiently than BDDs. Further, we propose special BDD/ZBDD operations for Petri nets which accelerate the manipulations of Petri nets. The approaches to handling Petri nets based on BDDs and ZBDDs are compared with several example nets, and it is shown that ZBDDs are more suitable for the symbolic manipulation of Petri nets.
A large number of models that are employed in the field of concurrent systems design, such as Petri Nets, gate-level circuits,
Static Data Flow Structures and Conditional Partial Order Graphs have an underlying static graph structure. Their semantics,
however, is defined using additional entities, e.g. tokens or node/arc states, which in turn form the overall state of the
system. We jointly refer to such formalisms as Interpreted Graph Models. The similarities in notation allow for links between different models to be created, such as interfaces between different
formalisms or conversion from one model type into another, which greatly extend the range of applicable analysis techniques.
This paper presents the new version of the Workcraft tool designed to provide a flexible common framework for development of Interpreted Graph Models, including visual editing,
(co-)simulation and analysis. The latter can be carried out either directly or by mapping a model into a behaviourally equivalent
model of a different type (usually a Petri Net). Hence the user can design a system using the most appropriate formalism (or
even different formalisms for the subsystems), while still utilising the power of Petri Net analysis techniques. The tool
is platform-independent, highly customisable by means of plug-ins, and is freely available for academic use.
In this paper a graphical editor to design Programmable Logic Controller (PLC) programs using Signal Interpreted Petri Nets
(SIPN) is presented. SIPN are an extension of condition event Petri nets that allow the handling of input and output signals.
The presented tool, SIPN Editor, has been developed using DiaGen which is an environment for rapidly developing diagram editors
from a formal specification of the diagram language. The SIPN Editor supports the translation of SIPN into input code for
the model checker SMV. Using SMV, the SIPN can be verified before it is automatically translated into Instruction List code
according to the IEC 61131-3 standard. This code can be downloaded on nearly every PLC.
This paper presents a unified model checking approach with Projection Temporal Logic (PTL) based on Normal Form Graphs (NFGs). To this end, a Modeling, Simulation and Verification Language (MSVL) is defined based on PTL. Further, normal forms and NFGs for MSVL programs and Propositional PTL (PPTL) formulas are defined. The finiteness for NFGs of MSVL programs is proved in details. Moreover, by modeling a system with an MSVL program p , and specifying the desirable property of the system with a PPTL formula ﾿ , whether or not the system satisfies the property (whether or not p ﾿ ﾿ is valid) can equivalently be checked by evaluating whether or not ¬( p ﾿ ﾿ ) ﾿ p ﾿ ¬ ﾿ is unsatisfiable. Finally, the satisfiability of a formula in the form of p ﾿ ¬ ﾿ is checked by constructing the NFG of p ﾿ ¬ ﾿ , and then inspecting whether or not there exist paths in the NFG.
This paper investigates the expressiveness of Propositional Projection Temporal Logic with Star (PPTL*). To this end, Büchi automata and ω-regular expressions are first extended as Stutter Büchi Automata (SBA) and Extended Regular Expressions (ERE) to include both finite and infinite strings. Further, by equivalent transformations among PPTL* formulas, SBAs and EREs, PPTL* is proved to represent exactly the full regular language. Moreover, some fragments of PPTL* are characterized, and finally, PPTL* and its fragments are classified into five different language classes.
This paper investigates the operational semantics of temporal logic programs. To this end, a temporal logic programming language called Framed Tempura is employed. The evaluation rules for both the arithmetic and boolean expressions are defined. The semantic equivalence rules for the reduction of a program within a state is formalized. Furthermore, the transition rules within a state and transition rules over an interval between configurations are also specified. Moreover, some examples are given to illustrate how these rules work. Thus, the executable behavior of framed programs can be captured in an operational way. In addition, the consistency between the operational semantics and the minimal model semantics based on model theory is proved in detail.
This work aims at designing and implementing logic control
structures that allow a combination of the advantages of classical
techniques for the development of programmable logic controller code and
elimination of disadvantages such as the lack of formal validation. This
paper introduces ordered color Petri nets in combination with some
extensions as a modeling tool for logic controllers. The validation of
both the model and the specifications of the logic control structures is
then pursued through a structural analysis of the net. A special
compiler that generates code according to the standard IEC 1131 is
discussed. The modeling and implementation of a logic control system of
a sector of a flexible assembly cell serves as an example
A practical decision procedure for propositional projection temporal logic with infinite models
- Duan