For automated manufacturing systems, the reachability graph analysis based on Petri nets faces with the state explosion challenge. This paper proposes an effective partial order technique for generalized system of simple sequential processes with unreliable resources by constructing improved weak-persistent graph. First, we review the partition technique of reachability graph which divides the marking type into legal and forbidden markings. Then, the definition of weak-persistent sets is introduced. Comparing with the original persistent set, the weak-persistent set achieves a better reduction in the state-space generation. However, it cannot be used directly in the system with unreliable resource due to uncontrollable transitions. Therefore, the concept of improved weak-persistent sets is proposed to reduce the reachability graph of generalized system of simple sequential processes with unreliable resources. Furthermore, it is showed that the improved weak-persistent graph can provide significant reduction compared with reachability graph while preserving all forbidden markings. Finally, the examples are given to demonstrate our method.

In an automated manufacturing system (AMS), resources are, in general, subject to unpredictable failures, which invalidate many existing deadlock control strategies. In this article, we propose an adaptive deadlock control policy for an AMS with multiple types of unreliable resources. The considered AMS is modeled with a system of simple sequential processes with resources. First, based on an elementary siphon control method, monitors are added for elementary siphons and some particular dependent siphons to ensure the liveness of a system if there are no resource failures. By considering the fact that an unreliable resource may fail in a system, recovery subnets are added to describe the resource failures and recoveries. Since a monitor added for a siphon may not be able to guarantee that the corresponding siphon is always marked if the failure of a resource in the siphon occurs, the concept of switch controllers is presented so as to make the siphon always remarked if it is emptied by resource failures. It is verified that the adaptive controller proposed in this article can guarantee the liveness of the controlled system no matter whether unreliable resources break down or not. More importantly, if there is no resource failure, the system can maintain predefined production without degrading planned system performance. Finally, examples are presented to illustrate the validity of the proposed method.

Abstract In this paper, we provide a non‐Markovian Stochastic Petri Net (SPN) model for D e v O p s w o r k f l o w specification, and we determine how business processes are carried out. After describing our model semantics, we show how general properties related to liveness and safety can be checked. After that, we provide several extensions on S P N s (SPN) the notation and expressivity to check some specific properties related to actors' (Developers and Operators) availability, interactions between the actors, and execution failures detection linked to the D e v O p s steps. Next, we validate the proposed model relevance with M A T L A B simulation through a specific D e v O p s case study. Finally, we propose a truncated density function to anticipate the delays related to the D e v O p s business process overall steps.

International audience

In most cities, the availability of parking is a major concern. The misuse of parking spots as drivers park for longer than permitted periods cause more delays, inconvenience to others, and even parking tickets. Moreover, the payment systems at many locations are still not electronic and rely on hard currency. The search for a parking space also contributes to congestion, pollution, and other safety issues. This paper introduces an end-to-end system that enables automatic car payments in a safe, private, secure, and efficient manner using Blockchain technology. The proposed solution utilizes Ethereum to prototype a solution which can facilitate the parking payments. In addition, Android auto and application modules that automate the payment process have also been developed. Moreover, a validation technique for enhancing the quality and correctness of the proposed solution, namely Model-Based Testing Techniques, has been discussed. The latter consists of deriving test suites from an adopted formal model, performing them, and assessing the correctness. The used formal model may combine both functional and load aspects. A list of techniques for improving the formal testing approach was identified. Besides, the authors explained how to manage dynamic adaptations of the system under test and how to use isolation strategies for avoiding interference between testing and business behaviors. Finally, an optimization phase for testers placement inspired by fog computing is proposed as well.

Patients with chronic conditions require medical care at their home. To this end, a smart follow-up and monitoring system is proposed, called Hapicare; which applies ontology-based uncertain reasoning over IoT sensors data and self-assessment. While similar approaches rely on certain events and rules, the proposed monitoring system is based on probabilistic reasoning that interleaves Bayesian and non-monotonic inference. The latter is defined by using rule-based on concepts of the Semantic Sensor Network (SSN) and the SNOMED-CT ontologies. This system also considers uncertain contextual information captured from sensors and the history of patients in order to better diagnose the current situation and trigger suitable reactions. It allows also handling overlaps between symptoms, the possibility of errors and hidden facts. Hapicare is developed in the context of Medolution EU project.

Due to extensive use and wear of equipment, the occurrence of failures in automated manufacturing systems (AMSs) remains inevitable. However, with maintenance policies, the reliability and availability of such systems can be increased. This paper presents different basic models based on stochastic Petri nets allowing the modeling of the integration of corrective and preventive maintenance in unreliable manufacturing systems and analysis of their effects on system's productivity. In all these models, we make sure that after having undergone a preventive or corrective operation, a resource is functioning normally. This property avoids the execution in the model of an infinite failure loop. Finally, we show how the proposed modeling of these maintenance strategies can be integrated in unreliable controlled manufacturing systems without causing failure-induced deadlocks.

We studied in this article a topic that focused on two areas of research: Constraint Satisfaction Problems (CSP) and genetic algorithms. The problem is that this type of algorithm is recognized to be greedy in terms of CPU time. To solve this problem, we tried to integrate the arc consistency (AC) at the initial population in a way that it would be the result of this filtering. First, we generated the genetic algorithm without integrating the arc consistency. Then, we considered that each chromosome is a CSP, each gene is a variable of the problem and each allele represents the taken value. We randomly generated the CSP to obtain the inconsistent values of each pair of variables. To remove these values, we used the technique of arc consistency as a technique for solving this type of problem, that means we have worked to eliminate from each variables domain the values which violate the constraint specific and make the CSP inconsistent. The aim of this work is to reduce performance in terms of execution time of the genetic algorithm.

This work focuses on a class of Petri nets (PNs) called Weighted Systems of Simple Sequential Processes with Resources (WS3PR). We study how to enforce liveness to WS3PR by appropriately allocating resources. A sufficient condition that guarantees liveness of a net system in this class is first derived. Then, based on such a condition, we propose an algorithm that computes an initial marking of resource places that guarantees the liveness of a WS3PR system where the initial marking of the idle places is given. Note that, we do not guarantee that the resulting solution is optimal, in the sense that a smaller initial marking of resource places that still leads to liveness could exist. However, several numerical examples show that the solution resulting from the proposed approach is optimal.

This work proposes a novel structure in Petri nets, namely data inhibitor arcs, and their application to the optimal supervisory control of Petri nets. A data inhibitor arc is an arc from a place to a transition labeled with a set of integers. A transition is disabled by a data inhibitor arc if the number of tokens in the place is in the set of integers labeled on it. Its formal definitions and properties are given. Then, we propose a method to design an optimal Petri net supervisor with data inhibitor arcs to prevent a system from reaching illegal markings with respect to control specifications. Two techniques are developed to reduce the supervisor structure by compressing the number of control places. Finally, a number of examples are used to illustrate the proposed approaches and experimental results show that they can obtain optimal Petri net supervisors for the net models that cannot be optimally controlled by pure net supervisors. A significant result is that the proposed approach can always lead to an optimal supervisor with only one control place for bounded Petri nets on the premise that such a supervisor exists.

Process mining refers to the extraction of process models from event logs. As real-life processes tend to be less structured and more flexible, clustering techniques are used to divide traces into clusters, such that similar types of behavior are grouped in the cluster. Educational process mining is an emerging field in the educational data mining (EDM) discipline, concerned with developing methods to better understand students' learning habits and the factors influencing their performance. However, the obtained models, usually, cannot fit well to the general students' behaviour and can be too large and complex for use or analysis by an instructor. These models are called spaghetti models. In the present work, we propose to use a two steps-based approach of clustering to improve educational process mining. The first step consist of creating clusters based employability indicators and the second step consist on clustering the obtained clusters using the AXOR algorithm which is based on traces profiles in order to refine the obtained results from the first step. We have experimented this approach using the tool ProM Framework and we have found that this approach optimizes at the same time, both the performance/suitability and comprehensibility/size of the obtained model.

No abstract available.

The main limitation of the verification approaches based on state enumeration is the state explosion problem. The partial order reduction techniques aim at attenuating this problem by reducing the number of transitions to be fired from each state while preserving properties of interest. Among the reduction techniques proposed in the literature, this article considers the stubborn set method of Petri nets and investigates its extension to time Petri nets. It establishes some useful sufficient conditions for stubborn sets, which preserve deadlocks and k-boundedness of places.

Context-aware systems are an emerging class of mobile computing systems aiming to provide ubiquitous access to information, communication and computation. These systems are able to sense and adapt automatically to the current environmental context. In this paper, we present a formal approach based on bigraphical reactive systems for modeling the main features of context-aware systems. The proposed formalism provides a clear separation between the part of the system which is affected by the context and the remaining part. In order to illustrate its potential, we apply our approach through a detailed case study of a smart car system.

We propose in this paper a workload-aware perform ability analysis of elastic server virtualized systems (SVS) based on non-Markovian SRN modeling approach. This analysis investigates correlations between several modules involving workload-aware power management (PM) mechanism, virtual machine (VM) and VM monitor (VMM) subject to aging, failure and rejuvenation. We show through numerical results how performance (i.e. waiting time), power usage as well as power-performance efficiency are impacted by power management attribute when using time varying workload with bursty nature. We show also how we can quantify PM attributes leading to small waiting time and a good utilization of the active power state.

This paper presents a new Petri net structure, namely, an interval inhibitor arc, and its application to the optimal supervisory control of Petri nets. An interval inhibitor arc is an arc from a place to a transition labeled with an integer interval. The transition is disabled by the place if the number of tokens in the place is between the labeled interval. The formal definition and the firing rules of Petri nets with interval inhibitor arcs are developed. Then, an optimal Petri net supervisor based on the interval inhibitor arcs is designed to prevent a system from reaching illegal markings. Two techniques are developed to simplify the supervisory structure by compressing the number of control places. The proposed approaches are general since they can be applied to any bounded Petri net models. A marking reduction approach is also introduced if they are applied to Petri net models of flexible manufacturing systems. Finally, a number of examples are provided to demonstrate the proposed approaches and the experimental results show that they can obtain optimal Petri net supervisors for some net models that cannot be optimally controlled by pure net supervisors. Furthermore, the obtained supervisor is structurally simple.

Enterprise service bus (ESB) is currently the most promising approach for business application integration in distributed and heterogeneous environments. Several commercial or open source ESB-based solutions have been proposed. To the best of our knowledge, none of these solutions has integrated the parallel processing by taking advantage of the multicore/multiprocessor technologies and thus improving greatly the ESB performance. In this paper, after describing the most important features of an enterprise service bus, we present a new massively parallel ESB (MPESB) architecture that meets this challenge.

The main problem of verification techniques based on exploration of (reachable) state space is the state explosion problem. In timed models, abstract states reached by different interleavings of the same set of transitions are, in general, different and their union is not necessarily an abstract state. To attenuate this state explosion, it would be interesting to reduce the redundancy caused by the interleaving semantics by agglomerating all these abstract states whenever their union is an abstract state. This article considers the time Petri net model and establishes some sufficient conditions that ensure that this union is an abstract state. In addition, it proposes a procedure to compute this union without computing beforehand intermediate abstract states. Finally, it shows how to use this result to improve the reachability analysis.

Cooperative diversity or virtual antenna arrays enables transmission range extension and provides performance enhancements in wireless Multi-hop relay networks, when compared with relaying non cooperative diversity based schemes. Moreover Cooperative diversity allows better reliability to link failure and lead to a more efficient transmission that is of particular interest in mobile environment. In this paper we present a quantitative approach to analyze the steady state availability analysis of a virtual antenna array link (VMIMO) subject to failures in a multi-hop wireless network using cooperative diversity and assuming Markovian properties. We propose an end to end VMIMO availability model enabling to express performance measure such as failure frequency and failure rate. These measures quantify failure impact on VMIMO link availability. Our model generalizes availability model given in [1] and may be exploited using the same approach presented in [1] to deduce survivability performance measures such that excess loss due to failure (ELF) and excess delay due to failure (EDF).

This paper develops a place invariant based deadlock prevention method to obtain an optimal Petri net supervisor by considering its implemental cost. A supervisor is expressed by control places and the arcs connecting control places to transitions. We assign an implemental cost for each control place and arc. Maximally permissiveness can be achieved by designing place invariants that make all legal markings reachable while all first-met bad marking unreachable. By solving an integer linear programming problem (ILPP), a set of optimal control places are obtained and the objective function is used to minimize the implemental cost of the final supervisor. A vector covering approach is used to reduce the number of constraints and variables in the ILPP, aiming to reduce the computational overhead of the proposed method. Finally, a number of examples are used to illustrate the proposed approach.

Abstract Providing optimal resource utilization while minimizing costs involved for wireless networks remains a challenging issue. Particularly mobilead hocenvironments subject to multi‐path fading and characterized by a dynamic topology need better resource management mechanisms. The focus of this paper is the performance evaluation of IEEE 802.11e MAC layer modeling under slow time‐varying Rayleigh fading channel via both layered and multi‐layered design approaches via a non‐Markovian Stochastic Petri Nets modeling. We propose two MAC IEEE 802.11e models considering service differentiation features. The first one is non cross‐layer based, whereas the second is cross‐layer based. The cross‐layer design approach adopted permits us to deal with both collisions and fading. We show the impact of the virtual load on the expected throughput. Compared to the conventional approach, our cross‐layered design approach provides significant performance gains. Copyright © 2010 John Wiley & Sons, Ltd.

With the maturing of service technology, most of organizations are implementing their business processes using Web-services (shortly SO-BPs). Nevertheless, still challenging engineering problems are hindering highly adaptive and realistic composite services. We are proposing a stepwise approach for this purpose. First, we are adopting a fine-grained activity-based perception, where we govern the semantics of any activity using event-driven business rules. We then conceptualize such activity-centric rules as transient architectural connectors. In terms of service-oriented architecture, connector roles will be playing service interfaces, whereas their glues be capturing the service composition logic. We further sketch how this modelling approach can be implemented using the aspectual .Net environment.

This paper propose a progressive and disciplined engineering of adaptive service-oriented business processes (SO-BPs). Each business activity is first informally governed through interaction-centric event-conditions-actions (ECA) based business rules. They are then smoothly conceptualized as transient ECA-driven architectural connectors, with roles playing service interfaces and glues capturing the service composition logic. This ECA-driven architectural conceptualization is formally validated using (still rule-centric) rewriting logic and its MAUDE language. From these founded, certified and adaptive SO-BPs, a compliant .NET based Web-services are systematically derived.

The focus of this paper is the IEEE 802.11e MAC layer modeling under slow time varying Rayleigh fading channel via both layered and multi-layered design approaches and through non Markovian Stochastic Petri Nets (NMSPN). In this paper, we carry out extensions to SPN IEEE 802.11 compact model reported in. Towards that, we investigate relaxation accounting for slow Rayleigh fading, service differentiation and cross-layer design. We propose two MAC IEEE 802.11e models including many of the EDCF extensions and accounting for slow Rayleigh fading. The first one is non cross-layer based whereas the second is cross-layer based. The cross-layer design approach adopted enables to not only manage collisions but also mitigate fading effects. We show the expected throughput behavior with respect to the virtual load at MAC level and the impact of service differentiation on MAC performance.

This paper deals with the problem of causal model-based diagnosis of distributed systems. The setting we consider is a collection of interacting behavioral Petri nets (BPNs). Each BPN model represents the causal behavioral model of one subsystem and its interactions with neighboring subsystems. Interactions among subsystems are modeled by tokens that pass from one model to another via common places. Diagnosis reasoning scheme exploits, in a first step a backward reachability analysis on each net model to obtain local diagnoses; and in a second step, it exploits a forward reachability analysis for ensuring that local diagnoses are consistent and form global ones.

Among all the different architectures being researched in the field of multi-agent systems, the mobile agent has shown to be one of the most challenging and most critical systems. With more applications being developed, there is a need to ensure large and complicated mobile agent systems are functioning correctly, with minimum or no errors. Moreover, the model-based testing technique has gained attention with the popularization of models in software design and development. Since the paradigm on nets within nets is well suited to express the dynamics of open mobile agents, it is retained as an abstract model from which abstract test cases are generated. Those test cases are then concretized and addressed to the system under test. The responses of the system under test are, finally, compared to the expected results derived from the abstract test model. As a case study, we modeled a packet world example on which different colored packets are scattered. Agents that live in this virtual world have to collect those packets and bring them to their right destination.

Link adaptation is an effective strategy in nature to achieve the ideal modulation to be selected depending upon signal quality at the terminals in wireless networks. In this paper, we examine the ability of the link adaptation to support cooperative transmissions. We present our proposal to improve the transmit performance within the framework of the 802.11 WLANs and discuss a switching criterion based on the best modulation which the source terminals may choose. Finally we conduct the performance evaluation and present simulation results to help understand the issues involved.

Traditional modelling and analysis of workflow aims at verifying the correctness of its control flow. When dealing with workflow security, the compliance of information flow with the adopted security policies needs also to be analyzed. In this paper, we propose a two-steps verification approach. While the first step is concerned by soundness of the workflow, the second one is concerned by the data consistency with respect to a multilevel security policy where the granting of access rights to objects by the workflow system is done according to information flow rules of Bell-LaPadula model. Our approach is based on the ECATNet formalism. It offers means to incorporate the security constraints on information flow into an initial WF net modeling the control flow of a workflow specification. We then show how to analyze the impact of the security rules on the whole Workflow through the model checker of the MAUDE environment and how to relax them before producing the correct specification and submitting it to the workflow system.

LfP (Language for Prototyping) is an ADL (Architecture Description Language) with a hierarchical and modular structure. In this paper, we propose tile logic (a rewriting logic extension) as a suitable semantic framework for this language. Indeed, it contributes to the formalization of LfP by providing a natural description for concurrency, synchronization and hierarchical composition aspects. A straight consequence of this work is the possibility to describe reconfigurable LfP architectures, and to handle with executable specification in Maude allowing hierarchical formal verification.

No abstract available.

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Summary form only given. This paper proposes a modeling approach easy to master in practice and from which one could directly derive a formal model capturing the main features of the dynamic interactions involved in multiagent systems (MAS). This approach follows two steps. The first consists to describe agent interactions in a MAS using Agent Unifying Model Language (AUML). The second step consists in translating this AUML description into a recursive colored Petri net (RCPN) model by following suitable rules. The choice of the RCPN formalism is motivated by its ability to model the dynamic agent planning ensuring the interleaving between planning and execution of complex actions and the availability of formal analysis and verification methods and tools.

The presented work is related to the use of structural Petri net techniques in the supervisory control of discrete event systems. A relevant property of the system behavior under supervision is to be behavior controllable (non-blocking), i.e., from any reachable state, it is always possible to reach a desirable state. In this paper, we present a proper supervisor synthesis method based on a purely structural reasoning. This parameterised method is especially well suited for a large class of discrete event systems called G-systems generalising well-known models presented in the literature. The system specification is obtained modularly by composing generic tasks and shared resources. Our main result is to prove that a given G-system is structurally non-blocking. This is achieved by preserving the Petri net property of "controlled siphon" through the composition of the generic tasks and resources.

In this paper we present a performance study of an input/output buffered type ATM switch with backpressure mechanism with an MMPP process as input. The backpressure is exerted at the Head of Line (HOL) level to prevent output buffer cell loss. MMPP process is chosen due to its bursty nature able to capture multimedia source characteristics such as data and voice. We propose an approximate method to calculate the total waiting time in the switch. Numerical examples will be given for two states MMPP to quantitatively show the effects of output buffer size b on performance switch. The analysis is done by using structured stochastic matrices of M/G/I type and the obtained results extend those related to scalar case (Poisson process).

This paper presents correctness proofs of Ada 95 preference control solution for the dining philosophers paradigm. Preference control is the ability to satisfy a request depending on the parameters passed in by the calling task and often also on the internal state of the server. In Ada 95, this schema is implemented with protected objects, entry families and requeue statements within the protected object. Our aim is to show that the preference control can be described in terms of states and transitions, similar to reactive automaton descriptions. This description, which can be done in terms of colored Petri nets, can lead jointly to validate the chosen implementation and to program it with protected objects and requeue statements of Ada 95. The paper is issued from an examination exercise for our students that have followed a course on Programming and Validation of Concurrent Applications and is presented in form of progressive steps for which the students were expected to give answer. The paper contains three programmed solutions and proofs of absence of deadlock and of starvation.