Construction Of Petri Nets Research Articles

CONCEPT OF BUILDING A LIBRARY OF TASKS AND SOLUTIONS

The article develops the concept of building a library of tasks and their solutions in the form of computational processes (CPs) and Petri nets (PNs) with the preliminary transformation of CPs into PNs. The conversion includes the extraction of macro operations (MOs) from CPs as a result of their analysis, the construction of PNs and their fragments as models of CPs and MOs, and the modeling of PNs and their fragments. The architecture, structure and interface of the library are proposed. Computational process is a sequence of time-ordered operations and procedures of varying degrees of complexity. The set of PNs, as well as the set of problems for which PNs are solutions, is divided into classes and subclasses. A class includes problems such as Combinatorial, Linear Algebraic Equations, etc.; the Combinatorial class includes subclasses of problems such as Sorting, Search, Sets, Graphs, etc. A macro operation is a fragment of a GP that is a functionally complete computational construct. MOs can have different levels of complexity, starting with the elementary one; they can be built hierarchically. A Petri net is a bipartite graph with two interconnected objects: event-condition, process-resource, etc. Fragments of the PN are models of the MO. The components of the library are tree nodes supplemented with files of their verbal descriptions built according to certain rules. The architecture, structure, interface, and operations of the library provide convenient management, editing, and expansion of knowledge about computational processes and macro operations, making the library open for further research and development by the developer. All files are available to the user, but without the right to edit. The paper presents an example of the initial filling of the library for the Sorting task.

Manufacturing Maps, a Novel Tool for Smart Factory Management Based on Petri Nets and Big Data Mini-Terms

This article defines a new concept for real-time factory management—manufacturing maps. Manufacturing maps are generated from two fundamental elements, mini-terms and Petri nets. Mini-terms are sub-times of a technical cycle, the time it takes for any component to perform its task. A mini-term, by definition, is a sub-cycle time and it would only make sense to use the term in connection with production improvement. Previous studies have shown that when the sub-cycle time worsens, this indicates that something unusual is happening, enabling anticipation of line failures. As a result, a mini-term has dual functionality, since, on the one hand, it is a production parameter and, on the other, it is a sensor used for predictive maintenance. This, combined with how easy and cheap it is to extract relevant data from manufacturing lines, has resulted in the mini-term becoming a new paradigm for predictive maintenance, and, indirectly, for production analysis. Applying this parameter using big data for machines and components can enable the complete modeling of a factory using Petri nets. This article presents manufacturing maps as a hierarchical construction of Petri nets in which the lowest level network is a temporary Petri net based on mini-terms, and in which the highest level is a global view of the entire plant. The user of a manufacturing map can select intermediate levels, such as a specific production line, and perform analysis or simulation using real-time data from the mini-term database. As an example, this paper examines the modeling of the 8XY line, a multi-model welding line at the Ford factory in Almussafes (Valencia), where the lower layers are modeled until the mini-term layer is reached. The results, and a discussion of the possible applications of manufacturing maps in industry, are provided at the end of this article.

Disentangling a complex response in cell reprogramming and probing the Waddington landscape by automatic construction of Petri nets

We analyzed the developmental switch to sporulation of a multinucleate Physarum polycephalum plasmodial cell, a complex response to phytochrome photoreceptor activation. Automatic construction of Petri nets representing finite state machines assembled from trajectories of differential gene expression in single cells revealed alternative, genotype-dependent interconnected developmental routes and identified reversible steps, metastable states, commitment points, and subsequent irreversible steps together with molecular signatures associated with cell fate decision and differentiation. Formation of cyclic transits identified by transition invariants in mutants that are locked in a proliferative state is remarkable considering the view that oncogenic alterations may cause the formation of cancer attractors. We conclude that the Petri net approach is useful to probe the Waddington landscape of cellular reprogramming, to disentangle developmental routes for the reconstruction of the gene regulatory network, and to understand how genetic alterations or physiological conditions reshape the landscape eventually creating new basins of attraction. Unraveling the complexity of pathogenesis, disease progression, drug response or the analysis of attractor landscapes in other complex systems of uncertain structure might be additional fields of application.

Modular construction of compact Petri net models

The use of modelling formalisms for the design of discrete event systems presents many advantages, such as the possibility of structural analysis of the model or performance evaluation. However, the difficulty of the process to obtain an appropriate model of the system requires the use of methodologies to ease the work of the designers. In this paper, two main subjects are discussed. On the one hand, the modular construction of Petri nets alleviates the design process by the use of blocks that can be assembled to build up a complete Petri net model. On the other hand, the development of decision support systems may require the assessment of the performance and properties of complete models obtained from different combinations of modular blocks. The formalism of the alternatives aggregation Petri net may help in the development of compact and efficient models that may reduce the use of scarce computer resources.

Modular construction of compact Petri net models

The use of modelling formalisms for the design of discrete event systems presents many advantages, such as the possibility of structural analysis of the model or performance evaluation. However, the difficulty of the process to obtain an appropriate model of the system requires the use of methodologies to ease the work of the designers. In this paper, two main subjects are discussed. On the one hand, the modular construction of Petri nets alleviates the design process by the use of blocks that can be assembled to build up a complete Petri net model. On the other hand, the development of decision support systems may require the assessment of the performance and properties of complete models obtained from different combinations of modular blocks. The formalism of the alternatives aggregation Petri net may help in the development of compact and efficient models that may reduce the use of scarce computer resources.

A Method of Sample Models of Program Construction in Terms of Petri Nets

In the article a method of automated construction of Petri nets simulating the behaviour of imperative programs is considered from the formal point of view. Petri net samples with certain characteristics are necessary in programming new algorithms for program analysis; in particular, they can be used for developing or optimizing algorithms of Petri nets compositions and decompositions, building the reachability tree, checking invariants and so on. The generation process consists of two stages. At the first stage, construction templates for a resulting net and parameters for construction are described. With the help of these parameters it is possible to regulate the final size and the absolute or relative amount of certain structures in the resulting net. At the second stage, iterative process of automated net construction is used for Petri net generation of any size, limited only by an available computer memory. In the first section of the article the minimum necessary definitions are given and a new version of Petri nets composition operation by places is introduced. Commutative and associative properties of introduced binary operation allow to synchronize any number of Petri nets in arbitrary order. Then construction template is defined as a marked Petri net with input and output interfaces and rules for templates composition using this interfaces. A number of construction templates can be united in a collection, for which the evolution rules are defined. The completeness property of a collection guarantees that the collection evolution results in a Petri net that simulates the imperative program behavior. The article provides a version of the construction templates complete collection and an example of Petri net simulating sequential imperative program construction.

A Petri Net-based Approach for Event Detection in Pedestrian Crossing Sequence

In this paper we present an approach to automatically detect anomalous traffic events like pedestrians crossing the junction, based on traffic video of low-level features such as size of the blob, spatial location, and velocity. The construction of Petri-Nets was used for both semantic description and event detection within traffic videos. The major novelties of this paper are extensions to both the modeling and the recognition capacities of Object Petri-Nets (PN). The detection of object level features are done with the help of state of art techniques like Gaussian Mixture of Models (GMM), and a series of Petri-Nets composed of various objects is proposed to describe the video content. The expected outcome of the proposed framework is that we can easily build semantic detectors based on PNs to search within traffic videos and identify interesting events. Experimental results based on recorded traffic video data sets and synthetic data sets are used to illustrate the potential of this framework.

Semantic Analysis of Field Sports Video using a Petri-Net of Audio-Visual Concepts

The most common approach to automatic summarization and highlight detection in sports video is to train an automatic classifier to detect semantic highlights based on occurrences of low-level features such as action replays, excited commentators or changes in a scoreboard. We propose an alternative approach based on the detection of perception concepts (PCs) and the construction of Petri-Nets, which can be used for both semantic description and event detection within sports videos. Low-level algorithms to detect PCs using visual, aural and motion characteristics are proposed, and a series of Petri-Nets composed of PCs is formally defined to describe video content. We call this a perception concept network–Petri-Net (PCN–PN) model. Using PCN–PNs, personalized high-level semantic descriptions of video highlights can be facilitated and queries on high-level semantics can be achieved. A particular strength of this framework is that we can easily build semantic detectors based on PCN–PNs to search within sports videos and locate interesting events. Experimental results based on recorded sports video data across three types of sports games (soccer, basketball and rugby), and each from multiple broadcasters, are used to illustrate the potential of this framework.

Transformations of Petri Nets

The aim of this paper is an introduction to the area of Petri net transformations, a rule-based approach for dynamic changes of the net structure of Petri nets. This is especially important for the stepwise construction of Petri nets in the sense of the software development process in software engineering. The concept of Petri net transformations is based on that of graph transformations and high-level replacement systems and it is introduced within a small case study logistics.

Automatic Unit Number Binding with Refrigeration Circuit Identification for Air-Conditioner Control Network

This paper proposes an automatic unit number binding method so that a number of logical subsystems are defined in the whole control network for distributed air-conditioners. Each air-conditioner unit starts the proposed algorithm at random timing to allocate its own unit number without any server. Then each outside unit one by one broadcasts the check signal and flows refrigerant gas to the refrigerant circuit between units to make each inside unit discover its piping connection. As a result, a number of logical subsystems are defined in the whole control network. A Petri net model was constructed for verification of our proposed system. For the case of two outside units and three inside units, the reachability to the required states and the deadlock free property were verified. The generalized module-by-module Petri net construction procedure shows applicability to general cases of arbitrary number of units.

A re-configurable multi-agent system architecture for error recovery in production systems

Multi-agent systems for manufacturing systems appear to provide adequate response to abrupt disturbances on the shop floor. To date, most of the work has been focused on planning and scheduling but very little work has been done on issues pertaining to monitoring, diagnostics and error recovery. Our approach addresses the issue of combining the discipline of hierarchical systems with the agility of multi-agent systems. Within the context of a hierarchy, the focus is on the workstation level and, in particular, the construction of a re-configurable system having production agents, error recovery agents, and a mediator agent structure connecting production and recovery agent hierarchies. In addition, the relationship to a multi-level, multi-layer hierarchy control is established. This latter hierarchy, based on Petri Net constructs, serves, in one sense, as a retrieval based resource for process planning and generation of recovery plans for production and recovery agents within the proposed multi-agent system. An objective of this effort is to provide a test-bed for comparison of hierarchical systems, heterarchical, and a hybrid combination which is the focus of the investigation presented here.

MODELING AND CONTROLLER SYNTHESIS FOR RESOURCE BOOKING PROBLEMS USING BDDS

Mixed Process algebra and Petri Nets (MPPN) combine Petri net constructs and Process algebra. The modeling language implies a compact representation of complex systems. For general resource booking problems MPPN is used for routing specifications and modeling of resources. These models are formally converted into ordinary Petri nets. The Petri net representations are easily converted into efficient Binary Decision Diagram (BDD). The BDDs are then used used for controller synthesis. It is shown that in specific cases very few boolean variables are required in the BDD representation based on MPPN. This is crucial in order to calculate a controller efficiently.

AN ALTERNATIVE APPROACH FOR MODELING OF INTERFERENCE IN DISCRETE-EVENT SYSTEMS

Simulation modeling represents a framework within which discrete-event systems such as construction processes can be analysed, designed and improved. Modeling of some characteristics inherent in general construction processes, however, is difficult. One such characteristic is interference. This paper proposes a construction process-based methodology developed from a Petri Net approach for the modeling of the behavior. This new methodology provides an intuitive approach by the addition of three new modeling elements to basic Petri Net constructs. The functionality of the new elements is described and the implementation of the proposed methodology is provided. The approach provides a means of reflecting reality and practicality in construction-process modeling. It properly addresses the consequences of interference in terms of what happens to the interfered activities and to the involved resources.

Approximate real-time decision making: Concepts and rough fuzzy Petri net models

This paper considers the construction of Petri nets to simulate the computation performed by decision systems. Algorithms are given to construct Petri nets which correspond to decision rules, information systems, and real-time decision systems. Rough as well as rough fuzzy Petri net extensions of colored and generalized fuzzy Petri nets are used to create highly parallel programs to simulate reasoning system computations. Constructed nets make it possible to evaluate the design of decision system tables, and to trace computations in rules derived from decision tables. Start places of nets are connected to Dill process receptors which await input from the environment. Time consumption during the propagation of outputs from sensors in a decision system is monitored with timers called approximate time windows, which measure durations between firings of decision transitions relative to time granules with names such as early, ontime, and late. Guards on decision transitions are propositional functions which permit a rule to fire for some sensor values and not for others. In addition, the design of guards makes allowance for multivalued logic, where conditional sensor readings are assessed in terms of their degree of membership in sensor measurement granules. In some cases, a rule can fire if the degree of truth of its guard (premise) is above some threshold. Through simulation, designers can arrive at reasonable estimates of the period of timers on decision transitions. The approach to simulating computations by decision systems presented in this paper results in fast, massively parallel programs implementable on a multiprocessor. © 1999 John Wiley & Sons, Inc.

Constructing petri net models using genetic search

The problem considered is that of constructing a Petri Net model of a particular device, process, or system described by observations of its interactions with its environment. The algorithm proposed for achieving a solution employs the principles of genetic search. Also presented is a detailed investigation of its operation, thereby affording a theoretical justification of its design. The expressive and representational power of Petri Nets renders them ideally suited to the modelling of many complex event systems. As a modelling language, they directly support the intrinsically difficult concepts of concurrent and parallel activities, synchronisation of events and the distribution of various resources. However, the development of a model of a significant system is laborious and circumstances of limited knowledge of the system's internal structure compound the difficulty. By composing the perceived stimuli and responses of the system under study as a set of behavioural requirements, the Petri Net construction problem can be examined. The inherently difficult nature of this problem renders most other approaches inapplicable or inadequate; the quest for a satisfactory solution leads instead to the development of an algorithm employing genetic search technology. Built around a genetics-based machine learning architecture, the first algorithm developed shows a deficiency in its dependence on the particular order in which various options are explored. Alleviating this difficulty through a simple modification may also hold a lesson for other classifier systems.