Petri Net Process Research Articles

An integrated Petri net-pseudo bond graph model for nuclear hazard assessment

A pseudo-bond graph is presented to model the heat transferred from the fuel rods to the coolant via its cladding in a generic nuclear reactor case study. Simulations performed using this model are used to explore the temperatures of the core components under ordinary and emergency scenarios, considering various conditions of coolant supply and reactor power output. The model is combined with a timed stochastic Petri net to produce a hybrid model, in which the reactor operation and fault status is determined by the Petri net and fed into the bond graph to examine the resulting impact on core temperatures, which in turn are fed back into the Petri net process. The results predict the distribution of the reactor operational durations before a disruption occurs. The model provides the temperature profiles attained by the cladding and fuel components, indicating a low probability of dangerous temperatures.

Improving Predictive Process Monitoring Through Reachability Graph-Based Masking of Neural Networks

Predicting the next event during process runtime is an objective of interest in predictive process monitoring (PPM). <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Decay replay mining</i> is one of few deep learning-based next event prediction approaches that are built upon process model notations. However, this algorithm does not fully intertwine its neural network with the available process knowledge contained in the process model. This work, which is an extended version of an earlier conference publication, investigates the reachability graphs of underlying Petri net process models for masking the neural network of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">decay replay mining</i> to ultimately increase the quality of next event predictions. A more comprehensive set of experiments is performed to provide robust statistical evidence of the usefulness of the approach and relativizes earlier made claims and hypotheses. In addition, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">decay replay mining</i> approach is applied with the suggested reachability graph-based masking extension to a healthcare use case of sepsis patients facilitating decision-making for healthcare practitioners. The obtained results further underscore the validity of the masking of neural networks using knowledge contained in the reachability graph of a Petri net process model.

Abstract processes in the absence of conflicts in general place/transition systems

Goltz and Reisig generalised Petri's concept of processes of one-safe Petri nets to general nets where places carry multiple tokens. BD-processes are equivalence classes of Goltz-Reisig processes connected through the swapping transformation of Best and Devillers; they can be considered as an alternative representation of runs of nets. Here we present an order respecting bijection between the BD-processes and the FS-processes of a countable net, the latter being defined—in an analogous way—as equivalence classes of firing sequences. Using this, we show that a countable net without binary conflicts has a (unique) largest BD-process.

Modeling and analysis of mission thread of weapon system of systems based on O-PPN

Aiming at the problem that the current WSoS mission modeling and analysis methods are difficult to describe the property of multi-state of each equipment system, combining with Petri net and Markov process, an O-PPN based mission thread modeling and analysis method is proposed in this paper. Based on the definition of WSoS, the mission of WSoS is formally described. To improve the traditional Petri net, an operation performance Petri net (O-PPN) is constructed, in order to meet the modeling needs of the general mission thread of the WSoS; and aiming at the problems of the performance degradation of the equipment system and the possible "ahead of time" state, the performance degradation model of the equipment system based on Markov is constructed. The corresponding state probability set is obtained by inputting the reliability parameters of each equipment system. And according to the requirements of each operation in the mission thread for the performance level of each equipment system and combined with the mission success and failure criteria of the combat task and operation, the mission success probability of the whole WSoS is calculated. Finally, the feasibility of the proposed method is verified by the simulation of the case.

Actantial Narrative Schema in Emergency Response Process Modeling for Aircraft Fires

Analyzing the emergency response process and time characteristics after aircraft fires is extremely important for airport safety. Due to nonprocess-related elements, the Petri net model of the emergency process is generally complex and difficult to revise and expand. In this study, the actantial model was used to analyze the semantic structure of emergency actions in the Petri net emergency process model, and the actantial-timed Petri net (A-TPN) hybrid model was proposed for problem solving. The emergency response process of aircraft fires was analyzed as a case study to explain the application steps of the A-TPN hybrid model. First, the types of elements should be divided into process-related elements and nonprocess-related elements. Process-related elements include status elements and narrative elements, which are equivalent to the places and transitions in the Petri net model. Second, the workflow constructed by the status and narrative elements is converted into a Petri net. An actantial model is used to analyze the semantic structure of emergency response action narratives. Third, according to the analysis of the actants of the helper and the opponent, emergency action time characteristics are considered to construct the A-TPN hybrid model and analyze the time performance of the emergency response process. In this way, an emergency response plan can be analyzed and promoted for smart development.

Decay Replay Mining to Predict Next Process Events

In complex processes, various events can happen in different sequences. The prediction of the next event given an a-priori process state is of importance in such processes. Recent methods have proposed deep learning techniques such as recurrent neural networks, developed on raw event logs, to predict the next event from a process state. However, such deep learning models by themselves lack a clear representation of the process states. At the same time, recent methods have neglected the time feature of event instances. In this paper, we take advantage of Petri nets as a powerful tool in modeling complex process behaviors considering time as an elemental variable. We propose an approach which starts from a Petri net process model constructed by a process mining algorithm. We enhance the Petri net model with time decay functions to create continuous process state samples. Finally, we use these samples in combination with discrete token movement counters and Petri net markings to train a deep learning model that predicts the next event. We demonstrate significant performance improvements and outperform the state-of-the-art methods on nine real-world benchmark event logs.

Full Axiomatisation of Timed Processes of Interval-Timed Petri Nets

In this paper we use partial order semantics to express the truly concurrent behaviour of Interval-Timed Petri nets (ITPNs) in their most general setting, i.e. with autoconcurrency and zero duration, as studied with its standard maximal step semantics in [1]. First we introduce the notion of timed processes for ITPNs inductively. Then we investigate if the equivalence of inductive and axiomatic process semantics - true for classical Petri nets - could hold for ITPNs too. We will see that the notions of independence and immediate firing obligation seem to be antagonistic ones, and that local axioms, adequate to define processes of classical Petri nets, are not sufficient to caracterize timed processes of ITPNs. We propose several original “global” axioms which reveal to be an effective solution. Thus we yield finally a full axiomatic definition of timed processes for ITPNs.

“Truly concurrent” and nondeterministic semantics of discrete-time Petri nets

In the paper, a "truly concurrent" and nondeterministic semantics is defined in terms of branching processes of discrete-time Petri nets (DTPNs). These nets may involve infinite numbers of transitions and places, infinite number of tokens in places, and (maximal) steps of concurrent transitions, which allows us to consider this class of DTPNs to be the most powerful class of Petri nets. It is proved that the unfolding (maximal branching process) of the DTPN is the greatest element of a complete lattice constructed on branching processes of DTPNs with step semantics. Moreover, it is shown that this result is true also in the case of maximal transition steps if additional restrictions are imposed on the structure and behavior of the DTPN.

A Petri net-based methodology to increase flexibility in service-oriented holonic manufacturing systems

Distributed control systems such as the holonic manufacturing systems and service-oriented architectures have demonstrated to provide higher levels of flexibility, notably in the planning and scheduling functionalities, if well exploited. In scheduling, the use of fixed process plans generated by traditional planning approaches, usually leads to unrealistic schedules due to the lack of considerations of the workshop status. IPPS approaches try to break the gap between these two functionalities in favor of providing flexible plans adapting to the shop floor's state. A key element in the creation of flexible process plans is the definition of a process model capable of representing alternatives solutions to the sequencing problem and therefore increasing the potential solution space. This paper presents a methodology to increase planning flexibility in service-oriented manufacturing systems (SOHMS). The methodology introduces a Petri net service-oriented process model (SOP model) capable of computing a product's deadlock free sequential space and adapts to the fractal character of holonic architectures. A set of modeling rules, with illustrations, is presented for the automatic generation of the Petri net, based on a set of precedence conditions. To explore the solution space represented by the SOP model a holonic interaction protocol is presented. Moreover, a set of behavioral strategies is proposed in order to cope with the effects of a possible combinatorial explosion. A study case applied workshop example is presented to illustrate the modeling process of SOP models, compute the sequential solution space and demonstrate how this notably increases the number of potentially goods feasible solutions.

Automation of Presentation Record Production Based on Rich-Media Technology Using SNT Petri Nets Theory.

Rich-media describes a broad range of digital interactive media that is increasingly used in the Internet and also in the support of education. Last year, a special pilot audiovisual lecture room was built as a part of the MERLINGO (MEdia-rich Repository of LearnING Objects) project solution. It contains all the elements of the modern lecture room determined for the implementation of presentation recordings based on the rich-media technologies and their publication online or on-demand featuring the access of all its elements in the automated mode including automatic editing. Property-preserving Petri net process algebras (PPPA) were designed for the specification and verification of the Petri net processes. PPPA does not need to verify the composition of the Petri net processes because all their algebraic operators preserve the specified set of the properties. These original PPPA are significantly generalized for the newly introduced class of the SNT Petri process and agent nets in this paper. The PLACE-SUBST and ASYNC-PROC algebraic operators are defined for this class of Petri nets and their chosen properties are proved. The SNT Petri process and agent nets theory were significantly applied at the design, verification, and implementation of the programming system ensuring the pilot audiovisual lecture room functionality.

A Method of Producing Protocol Minimum Complete Test Cases Based on Petri Net Process

Finding the minimum complete test cases to cover all the behaviors of the protocol by formalized model is the good method to solve protocol testing. A protocol test cases generation method is presented. The method can produce minimum complete test cases. It covers protocol behaviors as much as possible by test cases as little as possible. The basic idea of this method is: express protocol basic test case by Petri net basic process section, combine the test cases by operations such as connection, union and closure, then get the minimum complete test cases. With an example, give the method of producing minimum complete test cases based on LAPD protocol. This method makes the protocol test more accurate and intuitive.

Traffic Monitoring and Event Analysis Based on Integrated Multivideo and Petri Net Process

Decreasing traffic accidents and events are one of the most important responsibilities for all of the governments in the world. However, it is difficult to exactly measuring the traffic condition. To find out the root cause of traffic accidents and restore the occurrence of traffic events, a traffic monitor and event analysis mechanism based on multi-videos processing and Petri net analysis techniques is proposed. In which, the traffic information is collected through the deployment of cameras at intersection of heavy traffic area. After then, all of the collected information is provided for constructing multi-viewpoint traffic model. The significant features are extracted for traffic analyzing through Petri Net and detection of motion vector. Finally, decision will be output after integrated traffic information and event analysis. Experimental results demonstrate the feasibility and validity of our proposed mechanism. It can be applied as a traffic management system.

A Novel Approach to Evaluate the Stability of Production Manufacturing System Based on Petri-Net and Analytic Hierarchy Process

In the whole life cycle of production process, the stability of production manufacturing system is an important production factor. However, there were a few researches about the system stability in the past years. In this paper, for the stability of production manufacturing system, a new method is proposed based on Petri-net and analytic hierarchy process. In the proposed method, the reachability of manufacturing system is judged by using Petri-net, and the system stability is calculated by the successful probability of the key production nodes. Finally, evaluation steps of the new method are given, and the new evaluation method is applied in case study.

FACETA*: Checkpointing for Transactional Composite Web Service Execution based on Petri-Nets

Failures during the execution of Transactional Composite Web Services (TCWSs) can be repaired by forward or back–ward recovery processes, according to the component WSs transactional properties. In previous works, we presented TCWS fault tolerant execution approaches relying on WSs replacement, on a compensation protocol, and on unrolling processes of Colored Petri-Nets (CPNs) to support forward and backward recovery. We represent a TCWS and its corresponding backward recovery process by CPNs. Even though these recovery processes ensure system consistency, backward recovery means that users do not get the desired answer to their queries and forward recovery could imply long waiting time for users to finally get the desired response. In this paper, we present an alternative fault tolerant approach in which, in case of failures, the unrolling process of the CPN controlling the execution of a TCWS is check–pointed and the execution flow goes on as much as it is possible. In this way, users can have partial responses as soon as they are received and can re-submit the checkpointed CPN to re-start its execution from an advanced point of execution (checkpoint). We present the checkpointing algorithm integrated to our previous work.

A Multiset Rule Based Petri net Algorithm for the Synthesis and Secretary Pathway of Plasma Membrane - Glycoprotein

Membrane computing is a branch of Natural computing aiming to abstract computing models from the structure and functioning of the living cell. A comprehensive introduction to membrane computing is meant to offer both computer scientists and non-computer scientists an up-to date overview of the field. In this paper, we consider a uniform way of treating objects and rules in P Systems with the help of Multiset rewriting rules. Here the synthesis and secretary pathway of glycoprotein in epithelial cells of small intestine is considered as an example. A natural and finite link is explored between Petri nets and membrane Computing. A Petri net (PN) algorithm combined with P Systems is implemented for the synthesis and secretary pathway of Glycoprotein. To capture the compartmentalization of P Systems, the Petri net is extended with localities and to show how to adopt the notion of a Petri net process accordingly. The algorithm uses symbolic representations of multisets of rules to efficiently generate all the regions associated with the membrane. In essence, this algorithm is built from transport route sharing a set of places modeling the availability of system resources. The algorithm when simulated shows a significant pathway of safe Petri nets.

Formal Specification and Verification of Modular Security Policy Based on Colored Petri Nets

Security policies are one of the most fundamental elements of computer security. Current security policy design is concerned with the composition of components in security systems and interactions among them. Consequently, in a modular specification and verification of a policy, the composition of the modules must consistently assure security policies. A rigorous and systematic way to predict and assure such critical properties is crucial. This paper addresses the problem in a formal way. It uses colored Petri net process (CPNP) to specify and verify security policies in a modular way. It defines fundamental policy properties, i.e., completeness, termination, consistency, and confluence in Petri net terminology and gets some theoretical results. According to the eXtensible Access Control Markup Language (XACML) combiners and property preserving Petri net process algebra (PPPA), several policy composition operators are specified and property preserving results are stated for the policy correctness verification. As an application, the approach is illustrated for the design of Chinese Wall Policy.

Fuzzy Petri Nets for Human Behavior Verification and Validation

Regarding the rapid growth of the size and complexity of simulation applications, designing applicable and affordable verification and validation (V&V) structures is an important problem. On the other hand, nowadays human behavior models are principles to make decision in many simulations and in order to have valid decisions based on a reliable human decision model, first the model must pass the validation and verification criteria. Usually human behavior models are represented as fuzzy rule bases. In all the recent works, V&V process is applied on a ready given rule-base. In this work, we are first supposed to construct a fuzzy rule-base and then apply the V&V process on it. Considering the professor-student interaction as the case-study, in order to construct the rule base, a questionnaire is designed in a special way to be transformed to a hierarchical fuzzy rule-base. The constructed fuzzy rule base is then mapped to a fuzzy Petri net and then within the verification (generating and searching the reachability graph) and validation (reasoning the Petri net) process is searched for probable structural and semantic errors.

Interactive Web service composition based on Petri net

One of the most promising advantages of Web service technology is the possibility of creating value-added services by combining existing ones. For interactive services, sending and receiving an arbitrary number of messages may occur during a service process. It is important that the service composition is not only based on input/output interface, but also related to process behaviour. This paper deals with the problem of interactive Web service composition, ie, for a complex interactive composition schema, and how to discover and select concrete services to satisfy the requirements of users and service interaction. Firstly, a Web service is modelled as an open Petri net, with messages and inner process description, and the service interaction is achieved via asynchronous composition. Then, according to abstract composite service, concrete services are discovered by some rules. These rules include interface consistency, structural-characteristic preservation, which assures the correct interaction between services. With the help of Petri net language, the similarity degree of abstract and concrete services based on their interface and inner process is evaluated, which provides guides for service selection.

Adding Branching to the Strand Space Model

The strand space model is one of the most successful and widely used formalisms for analysing security protocols. This might seem surprising given that the model is not able to reflect choice points in a protocol execution: the key concept in the strand space model is that of a bundle, which models exactly one possible execution of a security protocol. Inspired by the branching processes of Petri nets, we show that branching can be introduced into the strand space model in a very natural way: bundles can be generalized to branching bundles, which are able to capture several conflicting protocol executions. Our investigations of the theory of branching bundles will motivate the concept of symbolic branching bundles, and culminate in the result that every protocol has a strand space semantics in terms of a largest symbolic branching bundle. We hope our results provide a strong theoretical basis for comparing models and providing process calculi semantics in security protocol analysis. Altogether our work is related but different to a series of works by Crazzolara and Winskel. Throughout we will profit from a close relationship of the strand space model to event structures, which has already been pointed out by these authors.

An algebraic characterization of independence of Petri net processes

The paper is concerned with processes of Petri nets. A partial operation on such processes is defined that allows one to concatenate processes whenever one process is a continuation of another. It is shown that for any Petri net as defined in the paper its set of processes equipped with this operation forms a category in which independence of processes can be characterized in a natural, purely algebraic way.