Showing papers on "Process architecture published in 2017"

Verification of State-Based Opacity Using Petri Nets

Abstract: A system is said to be opaque if a given secret behavior remains opaque (uncertain) to an intruder who can partially observe system activities. This work addresses the verification of state-based opacity in systems modeled with Petri nets. The secret behavior of a system is defined as a set of states. More precisely, two state-based opacity properties are considered: current-state opacity and initial-state opacity . We show that both current-state and initial-state opacity problems in bounded Petri nets can be efficiently solved by using a compact representation of the reachability graph, called basis reachability graph (BRG). This approach is practically efficient since the exhaustive enumeration of the reachability space can be avoided.

Compact Supervisory Control of Discrete Event Systems by Petri Nets With Data Inhibitor Arcs

Abstract: 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.

A Necessary and Sufficient Condition for a Resource Subset to Generate a Strict Minimal Siphon in S 4PR

Abstract: Systems of sequential systems with shared resources (S4PR) represent a class of Petri nets that have powerful modeling capability for resource allocation systems. Their efficient siphon computation is important. An open issue is how to determine whether a resource subset can generate a strict minimal siphon (SMS). This paper presents the answer. In particular, we propose a new concept called characteristic implicit resource-transition nets. By charactering such nets, we successfully establish a necessary and sufficient condition for a resource subset to generate an SMS.

Design and Verification of Real-Life Processes With Application of Petri Nets

Abstract: This paper focuses on the design and verification methods of distributed logic controllers supervising real-life processes. Such systems have to be designed very carefully and precisely in order to operate flawlessly and to meet user needs. We propose to use interpreted Petri nets as modeling formalism. A new design flow of distributed logic controllers is introduced. The methodology covers the development process from the specification stage to the final implementation of the controller in the distributed devices. In the proposed solution, the system is decomposed into separate modules that form a distributed system. Furthermore, the specification (before and after the decomposition process) is formally verified with the application of the model checking technique against predefined behavioral requirements. Finally, the system is implemented in real devices. The usage of formal methods and double model checking ensure the correct functionality of the designed distributed logic controller. The theoretical approach is supplemented by the practical experiments. Furthermore, the proposed idea is illustrated by an example of a smart home system.

Fully Expanded Tree for Property Analysis of One-Place-Unbounded Petri Nets

Abstract: This paper proposes a fully expanded tree (FET) approach for one-place-unbounded Petri nets. The FET of a one-place-unbounded Petri net consists of all and only reachable markings from its initial marking. Its applications to liveness and deadlock analysis for such Petri nets are developed. The proposed method has a larger application scope than all the existing methods for them. Several examples are provided to show its superiority over the state-of-the-art methods.

On the Decidability and Complexity of Diagnosability for Labeled Petri Nets

Abstract: In this paper, we investigate the decidability and complexity of the fault diagnosis problem in unbounded labeled Petri nets. First, we show that checking diagnosability for unbounded Petri nets is decidable. We present a new necessary and sufficient condition for diagnosability, which can be reduced to a model checking problem for unbounded Petri nets. Then, we show that checking diagnosability for unbounded Petri nets is EXPSPACE-complete. This complexity result is further extended to various subclasses of Petri nets. To the best of our knowledge, this is the first paper that establishes decidability and complexity results for diagnosability of unbounded Petri nets.

An improved approach to test diagnosability of bounded petri nets

Abstract: For bounded Petri nets, Cabasino et al. propose a diagnosability test method that is based on the analysis of a modified basis reachability graph and a basis reachability diagnoser. However, its complexity is exponential in the number of nodes of the basis reachability diagnoser. In order to reduce the complexity of their method, this paper presents a new diagnosability test approach for bounded Petri nets. We present the concept of an extended basis reachability graph and prove that our approach is of polynomial complexity in the number of nodes of extended basis reachability graphs. An example is given to illustrate the application of the presented approach.

Detecting Data Inconsistency Based on the Unfolding Technique of Petri Nets

Abstract: The errors of data inconsistency occur in a concurrent system when some concurrent operations are conducted improperly. The model-checking technique is widely used to detect them based on the state transition graph. However, the state space explosion problem is the biggest obstacle for this technique, since the state transition graph is based on the interleaving semantics that can result in a rapid increase of the graph scale. In addition, data inconsistency is closely related with concurrent operations, but the state transition graph hardly characterizes concurrency due to its interleaving semantics. The unfolding technique of Petri nets can both alleviate the state explosion and characterize concurrency because it is based on the concurrent semantics. In this paper, we define Petri net with data to model concurrent systems with three kinds of data operations: read , write, and delete , and then formalize data inconsistency . We propose an unfolding method to produce a finite complete prefix (FCP) for each PD-net. Then, a matrix that represents all concurrency relations of transitions is constructed in view of FCP. Furthermore, the error of data inconsistency can be detected via this matrix. The related algorithms and the developed tool are introduced, and experiments illustrate their effectiveness and advantages. An example of industrial information system shows the usefulness of our study.

The Logical View on Continuous Petri Nets

Abstract: Continuous Petri nets are a relaxation of classical discrete Petri nets in which transitions can be fired a fractional number of times, and consequently places may contain a fractional number of tokens. Such continuous Petri nets are an appealing object to study, since they over-approximate the set of reachable configurations of their discrete counterparts, and their reachability problem is known to be decidable in polynomial time. The starting point of this article is to show that the reachability relation for continuous Petri nets is definable by a sentence of linear size in the existential theory of the rationals with addition and order. Using this characterization, we obtain decidability and complexity results for a number of classical decision problems for continuous Petri nets. In particular, we settle the open problem about the precise complexity of reachability set inclusion. Finally, we show how continuous Petri nets can be incorporated inside the classical backward coverability algorithm for discrete Petri nets as a pruning heuristic to tackle the symbolic state explosion problem. The cornerstone of the approach we present is that our logical characterization enables us to leverage the power of modern SMT-solvers to yield a highly performant and robust decision procedure for coverability in Petri nets. We demonstrate the applicability of our approach on a set of standard benchmarks from the literature.

Statistical Model Checking for Hybrid Petri Nets with Multiple General Transitions

Abstract: The modeling formalism of hybrid Petri nets allows investigating the dependability of e.g. critical infrastructures with hybrid characteristics. Hybrid Petri nets can model random delays with so-called general transitions. Approaches for analyzing such Petri nets are available for models with one or two general transitions, which change the discrete marking of the system by firing only once. We extend the formalism to more general transitions that possibly fire multiple times. This work provides a definition of the probability space for the evolution of hybrid Petri nets over time and presents an efficient approach to discrete-event simulation. Statistical Model Checking techniques are introduced to verify complex properties on hybrid Petri nets. The presented methods are implemented in Java and we show their feasibility in a case study that also serves to validate our results.

Dynamical Scheduling and Robust Control in Uncertain Environments with Petri Nets for DESs

Abstract: This paper is about the incremental computation of control sequences for discrete event systems in uncertain environments where uncontrollable events may occur. Timed Petri nets are used for this purpose. The aim is to drive the marking of the net from an initial value to a reference one, in minimal or near-minimal time, by avoiding forbidden markings, deadlocks, and dead branches. The approach is similar to model predictive control with a finite set of control actions. At each step only a small area of the reachability graph is explored: this leads to a reasonable computational complexity. The robustness of the resulting trajectory is also evaluated according to a risk probability. A sufficient condition is provided to compute robust trajectories. The proposed results are applicable to a large class of discrete event systems, in particular in the domains of flexible manufacturing. However, they are also applicable to other domains as communication, computer science, transportation, and traffic as long as the considered systems admit Petri Nets (PNs) models. They are suitable for dynamical deadlock-free scheduling and reconfiguration problems in uncertain environments.

Property-Preserving Generation of Tailored Benchmark Petri Nets

Abstract: Bottleneck of the validation and evaluation of analysis and verification tools for distributed systems is the shortage of benchmark problems. Specifically designed benchmark problems are typically artificial, rare, and small, and it is difficult to guarantee challenging properties of realistic benchmarks. This paper shows how to systematically construct arbitrarily complex Petri Nets with guaranteed safety properties. Key to our construction is a top-down parallel decomposition based on lightweight assumption commitment specifications. We will illustrate how a specific strategy for design choices, which may well be automated, leads to benchmarks that grow exponentially with the number of its parallel components, and that are very difficult to verify. In particular, we will report numbers from a systematic sequence of concrete corresponding verification attempts using today's leading verification technology.

Evaluation of Cyber Security and Modelling of Risk Propagation with Petri Nets

Abstract: This article presents a new method of risk propagation among associated elements. On thebasis of coloured Petri nets, a new class called propagation nets is defined. This class providesa formal model of a risk propagation. The proposed method allows for model relations betweennodes forming the network structure. Additionally, it takes into account the bidirectional relationsbetween components as well as relations between isomorphic, symmetrical components in variousbranches of the network. This method is agnostic in terms of use in various systems and it canbe adapted to the propagation model of any systems’ characteristics; however, it is intentionallyproposed to assess the risk of critical infrastructures. In this paper, as a proof of concept example, weshow the formal model of risk propagation proposed within the project Cyberspace Security ThreatsEvaluation System of the Republic of Poland. In the article, the idea of the method is presented aswell as its use case for evaluation of risk for cyber threats. With the adaptation of Petri nets, it ispossible to evaluate the risk for the particular node and assess the impact of this risk for all relatednodes including hierarchic relations of components as well as isomorphism of elements.

Petri Net Models and Collaborativeness for Parallel Processes with Resource Sharing and Message Passing

Abstract: Petri nets are widely used to model and analyse concurrent systems There exist two distinct classes of Petri nets that focus on different features of concurrent systems The first one features multiple parallel processes sharing a group of common resources but not interacting/collaborating with each other The second one allows multiple parallel processes to interact/collaborate with each other via message exchange but does not share any common resources However, in many distributed environments, multiple processes both interact/collaborate with each other and share some common resources To model and analyse such systems, this article defines a new class of Petri nets called Parallel Process Nets (P2Ns) that may be viewed as a generalization of the two mentioned above We propose collaborativeness and close collaborativeness for P2Ns The former guarantees that a modelled system is both deadlock-free and livelock-free, and the latter guarantees that it is deadlock-free, livelock-free, and starvation-free These concepts and ideas are illustrated through some classical examples such as Producer-Consumer Problem and Dinning Philosophers Problem Algorithms are developed to decide them At last, P2Ns are applied to the modelling and analysis of two real systems: hospital information system and elevator scheduling system

Petri Nets Repository: A Tool to Benchmark and Debug Petri Net Tools

Abstract: For a given scientific community, being able to use a common and rich accepted benchmark for the evaluation of algorithms and prototypes is an added value. The goal of this paper is to present Petri Nets Repository, an open Petri nets models database. It offers two main ways to navigate through the benchmark using criteria related to Petri net properties: a Web interface, and a Web service API (REST). So far, this database embeds the models from the Model Checking Contest, as well as those of the discontinued Petriweb.

Petri nets and dynamic causality for service-oriented computations

Abstract: When dealing with service oriented computations the dependencies among the various distributed activities may be complex and difficult to represent statically. Recently Event Structures where the causality may change dynamically have been introduced and have been related with many other kind of Event Structures (with a particular focus on expressivity). In this paper we relate them to a kind of (labeled) Petri net which turns out to cover these new Event Structures. This relationship empowers the usage of all the available verification tools based on Petri nets, giving practical and usable means for the verification of the complex and distributed system whose behavior is modeled by this kind of event structures.

Liveness Analysis of $\omega $ -Independent Petri Nets Based on New Modified Reachability Trees

Abstract: Liveness of Petri nets means all activities in a modeled system can potentially take place and thus implies deadlock freedom. The research on liveness analysis approaches is inadequate. This paper proposes a liveness judgment reachability graph (LJRG) approach to analyze the liveness of $ {\omega }$ -independent Petri nets. Such nets can be loosely explained as a class of unbounded Petri nets in which the changes of tokens in unbounded places are not related to each other. This paper proposes several algorithms to transform a new modified reachability tree to a new modified reachability graph and then transform it to an LJRG. It then develops the application of LJRG into the liveness analysis of $ {\omega }$ -independent unbounded Petri nets. The proposed method provides a new theoretical method and important tool for the liveness analysis of unbounded Petri nets. It is illustrated via some examples.

Unified enhanced time Petri net models for development of the reactive applications

Abstract: The reactive application development requires models that comprise continuous and logic variables, and reacts continuously and asynchronously to external and internal events. The newly proposed models called Unified Enhanced Time Petri Nets (UETPNs) endow the transitions of Time Petri Nets (enhanced with input and output channels) with mappings that include fuzzy logic features and arithmetic operations. The mappings are used to control the flow of the execution and to calculate the model states. The places have assigned real variables and so the contained tokens are real numbers. Extending the classical fuzzy logic sets with the empty set allows the construction of fuzzy logic rule sets that can model besides the fuzzy Petri nets capabilities the inhibitor arcs and reset arcs. The UETPN can model concurrency, selection, reaction to internal and external events and temporal behavior with fixed and variable delays. An algorithm to execute the UETPN models is provided with some examples of its use for application developments.

Composition of Logical Petri Nets and Compatibility Analysis

Abstract: Logical Petri nets (LPNs) can well describe and analyze batch processing functions and pass the value indeterminacy in cooperative systems. Their structure is simpler than their equivalent inhibition PNs. To analyze them, a vector matching method was given previously. We present interactive LPNs (ILPNs) in this paper. Their liveness and boundedness are analyzed for the first time. Compatibility is analyzed for a composed system and reflects the possibility of correct/proper interactions among its subsystems. To characterize different cooperative abilities in practice, compatibility is defined for ILPNs. Some relationships among compatibility, liveness, boundedness, and conservativeness are revealed. An example is presented to discuss the effectiveness of the proposed method.

A Minimal Supervisory Structure to Optimally Enforce Liveness on Petri Net Models for Flexible Manufacturing Systems

Abstract: This paper presents a new method of computing a minimal supervisory structure that optimally enforces liveness on the Petri net models for flexible manufacturing systems (FMSs). The proposed method utilizes the structural properties of a Petri net model to avoid the computation of its reachability graph, which in general leads to the state explosion problem. This paper aims to design a single control place for each concurrent process of a Petri net model or a sub-net model, which thus provides a constant number of control places in a supervisor regardless of the number of resource places in a Petri net or sub-net model. It is shown that the structural size of a supervisor is minimal as the number of control places depends on the number of concurrent processes in the Petri net model. Precisely, two algorithms are developed in this paper. The first aims to compute active uncontrolled transitions and the second is concerned with a method to compute the generalized mutual exclusion constraints (GMECs) for each process of the Petri net model of an FMS. Furthermore, it provides an approach to design control places for each computed GMEC without solving integer linear programming problems, which greatly reduces the computational costs. When the computed control places are coupled with the uncontrolled Petri net model for an FMS, it optimally enforces liveness behavior of the Petri net model, and hence ensures the high utilization of resources in a considered system.

Business process modelling using ARIS: process architecture

Abstract: Purpose Academic libraries have witnessed huge changes due to internal and external factors. Recent evidence shows that there is a lack of interest in process analysis within academic libraries. There is a lot written on the need to change academic libraries but there is little analytical research that investigates processes, in terms of the process architecture. The paper aims to discuss this issue. Design/methodology/approach The modelling tool used is Architecture of Integrated Information Systems (ARIS). Findings ARIS can provide a process architecture and design for academic libraries that might raise questions later about procedures and some inefficiencies. Research limitations/implications Library managers might need to learn new techniques. Originality/value There is a lot written on the need to change academic libraries but there is little analytical research that investigates processes, in terms of the process architecture. This research examines business process modelling for academic libraries, focusing on the process architecture, as a way of visualizing, understanding and documenting processes.

Synthesis and Analysis of Process Networks by Joint Application of P-graphs and Petri Nets

Abstract: Due to the increasing complexity of human developed systems computer aid plays key role in engineering design involving process synthesis and analysis. The P-graph framework provides effective algorithms implemented in software to synthesize optimal process systems constructed from potential building blocks leading from the available resources to the desired targets. P-graph software computes both the optimal structure and the optimal parameter values of a process system, however, does not provide information on the dynamics of the system synthesized. In contrast Petri nets are tools for simulation and analysis of complex systems’ dynamic behavior. They can model the operation of a preliminarily well-defined process network, but they are inappropriate for synthesizing the optimal process structure.

Model checking multi-level and recursive nets

Abstract: With the increasing complexity of the problems and systems arising nowadays, the use of multi-level models is becoming more frequent in practice. However, there are still few reports in the literature concerning methods for analyzing such models without flattening the multi-level structure. For instance, several variants of multi-level Petri nets have been applied for modeling interaction protocols and mobility in multi-agent systems and coordination of cross-organizational workflows. But there are few automated tools for analyzing the behavior of these nets. In this paper we explain how to detect faults in models based on a representative class of multi-level nets: the nested Petri nets. We translate a nested net into a verifiable model that preserves its modular structure, a PROMELA program. This allows the use of SPIN model checker to verify properties related to termination, boundedness and reachability.

Computation of an Optimal Transformed Linear Constraint in a Class of Petri Nets With Uncontrollable Transitions

Abstract: Deciding how to prevent discrete event systems (DESs) from reaching forbidden states is an important problem in the field of DES supervisory control. For DESs with uncontrollable events, linear constraint transformation becomes a popular technique for solving the forbidden state problem when Petri nets are used as a modeling tool and control specifications are given in the form of linear constraints. This paper proposes a novel linear constraint transformation approach that is applicable to PT-ordinary Petri nets with uncontrollable subnets being forward-concurrent-free. For such nets, a linear constraint can be transformed into an optimal transformed one (i.e., a linear constraint that exactly characterizes the admissible marking set) by using the proposed approach, which is computationally shown to be of polynomial complexity with respect to the net size. An example is presented to illustrate the developed technique.

Efficient modeling and performance analysis for IEEE 802.15.4 with coloured Petri nets

Abstract: IEEE 802.15.4 is the standard protocol for low-rate, low-power wireless personal area networks, including the physical layer and media access control layer specifications. Particularly, some mechanisms for certain purposes, such as transmission efficiency and power saving, are introduced. It is worthwhile to evaluate how the protocol can fulfill the quality of service requirements. Coloured Petri nets are chosen for the modeling and analyzing purposes because of the enhanced modeling power and abundant analysis techniques. The modeling method for wireless network protocols using coloured Petri nets is summarized, which is general enough and can be directly used to model various wireless network protocols like IEEE 802.15.4. During the modeling process, some modeling techniques are utilized, e.g., building the model in the hierarchical and modular way, reducing the model by the folding technique, and normalizing the modeling process by the modeling patterns. Simulation is conducted on the coloured Petri net model to compute some performance metrics such as throughput, delivery ratio, delay, and energy cost. All the above show that coloured Petri nets can play an important role in modeling and analyzing wireless network protocols.

Fractal Petri nets

Abstract: During the last decade a new kind of dynamic architectural models and algorithms for system scalability has emerged. The dynamic scalability is one of the most important design goals for developers of distributed systems and cloud computing. We introduce Fractal Petri nets (FP-nets) that takes into account the dynamically scalable distributed architectures. FP-nets are a backward compatible extension of Petri Nets on the base of algebraic structure. FP-nets are synthesized from the initial marking Petri net by replication. FP-nets are considered as distributed. Well-known techniques for analysis of Petri net theory are adjusted to FP-nets. New techniques for modeling distributed resources named “token-stub” are suggested. The distributed IT resources are integrated into the architectures of FP-nets. Three FP-nets architectures such as layered, folded, and unfolded are proposed. A FP-net avoids the scalability problems. There are properties of FP-nets: scalability, self-similarity, and token-stub dependences. FP-nets can be highly recommended for automatic modeling dynamically scalable distributed architectures.

Matrix Representations for Ordinary Restricted Place Transition Nets

Abstract: Matrix representation provides for a concise representation of restricted or simple Petri nets and place transition nets. This main property is often ignored. Matrices are useful for identifying basic fundamental properties that are mainly related to the static structure of a net as presented in this work. Matrices can be used for identifying some very important basic properties. This paper contains the following sections: i) introduction, ii) motivation and problem why matrices can be used to represent basic petri nets iii) incidence matrix representation types for Petri nets iv) basic Petri net properties in terms of matrices are defined, discussed and explained v) simple examples of the properties observed from the matrices are given. Finally vi) some useful observations and vii) conclusions are given.

Quantifying the advantage of a kitting system using Petri nets: a case study in Turkey, modeling, analysis, and insights

Abstract: In case a paradigm is introduced to improve the operation of manufacturing systems, it is important to anticipate the performance of the system before expensive and time-consuming implementation. In this study, we provide the use of Petri nets in order to quantify the possible advantage of kitting feeding method in an assembly line through a case study. In particular, Petri nets have been developed through the integration of the resource-oriented and process-oriented modeling approaches and then a detailed quantitative analysis of the current and proposed system have been performed. The results and the analysis obtained from the Petri nets are used to give an idea about the anticipated performance of the proposed system before a possible implementation. Therefore, results can easily be used to aid decision-making.