Can I find a partner? Undecidability of partner existence for open nets

We study open nets as Petri net models of web services, with a link to the practically relevant language WS-BPEL. For those nets, we investigate the problem of operability which we consider as fundamental as the successful notion of soundness for workflow nets, i.e., Petri net models of business processes and workflows. While we could give algorithmic solutions to the operability problem for subclasses of open nets in earlier work, this article shows that the problem is in general undecidable.     

Verifying soundness of business processes: A decision process Petri nets approach

This paper presents a trajectory-tracking approach for verifying soundness of workflow/Petri nets represented by a decision-process Petri net. Well-formed business processes correspond to sound workflow nets. The advantage of this approach is its ability to represent the dynamic behavior of the business process. We show that the problem of finding an optimum trajectory for validation of well-formed business processes is solvable. To prove our statement we use the Lyapunov stability theory to tackle the soundness verification problem for decision-process Petri nets. As a result, applying Lyapunov theory, the well-formed verification (soundness) property is solved showing that the workflow net representation using decision process Petri nets is uniformly practically stable. It is important to note that in a complexity-theoretic sense checking the soundness property is computationally tractable, we calculate the computational complexity for solving the problem. We show the connection between workflow nets and partially ordered decision-process Petri net used for business process representation and analysis. Our computational experiment of supply chains demonstrate the viability of the modeling and solution approaches for solving computer science problems.     

Zero-Safe Nets: Comparing the Collective and Individual Token Approaches

The main feature of zero-safe nets is a primitive notion of transition synchronization. To this aim, besides ordinary places, called stable places, zero-safe nets are equipped with zero places, which in an observable marking cannot contain any token. This yields the notion of transaction: A basic atomic computation, which may use zero tokens as triggers, but defines an evolution between observable markings only. The abstract counterpart of a generic zero-safe net B consists of an ordinary P/T net whose places are the stable places of B and whose transitions represent the transactions of B. The two nets offer the refined and the abstract models of the same system, respectively, where the former can be much smaller than the latter, because of the transition synchronization mechanism. Depending on the chosen approach—collective vs individual token philosophy—two notions of transaction may be defined, each leading to different operational and abstract models. Their comparison is fully discussed on the basis of a multicasting system example. In the second part of the paper, we make use of category theory to analyze and motivate our framework. More precisely, the two operational semantics of zero-safe nets are characterized as adjunctions, and the derivation of abstract P/T nets as coreflections.     

Structural soundness of workflow nets is decidable

The problem of deciding whether a given workflow net is k-sound for some k?1 is known as structural soundness. We prove that structural soundness of workflow nets is decidable.     

Verification of Estelle-Specified Communication Protocols Using High-Level Petri Nets

Estelle specifications are considered that include certain dynamic constructs. A method of translation of these specifications into modified colored Petri nets is described. Static Estelle specifications are translated into hierarchical typed time nets (HTT nets), which are extensions of safe colored Petri nets through the introduction of the notions of time, priorities, and places (which are queues of tokens). A program complex EPV is presented that is designed for verification of static Estelle specifications of communication protocols by translating them into HTT nets. Experiments are described on simulation and search for semantic errors in protocols used in practice.     

On generating ⁎-sound nets with substitution

We present a method for hierarchically generating sound workflow nets by substitution of nets with multiple inputs and outputs. We show that this method is correct and generalizes the class of nets generated by other hierarchical approaches. The method involves a new notion of soundness which is preserved by the generalized type of substitution that is presented in this paper. We show that this notion is better suited than ⁎-soundness for use with the presented type of generalized substitution, since ⁎-soundness is not preserved by it. It is moreover shown that it is in some sense the optimal notion of soundness for the purpose of generating sound nets by the presented type of substitution.     

On the ω-language Expressive Power of Extended Petri Nets

In this paper, we study the expressive power of several monotonic extensions of Petri nets. We compare the expressive power of Petri nets, Petri nets extended with non-blocking arcs and Petri nets extended with transfer arcs, in terms of ω-languages. We show that the hierarchy of expressive powers of those models is strict. To prove these results, we propose original techniques that rely on well-quasi orderings and monotonicity properties.     

Analysis of railway stations by means of interval timed coloured Petri nets

In this paperinterval timed coloured Petri nets ((van der Aalst, 1993)) are used to model and analyse railway stations. We will show that this approach can be used to evaluate both station operating schedules and the infrastructure of a station.An interval timed coloured Petri net (ITCPN) is a coloured Petri net extended with time; time is in tokens and transitions determine a delay for each produced token. This delay is specified by an upper and lower bound, i.e. an interval. The ITCPN model allows for the modelling of the dynamic behaviour of large and complex systems, without loosing the possibility of formal analysis. In addition to the existing analysis techniques for coloured Petri nets, we use a new analysis method to analyse the temporal behaviour of the net. This method constructs a reduced reachability graph and exploits the fact that delays are described by an interval. We will also discuss other (Petri net based) methods that can be used to analyse railway stations.By order of and in co-operation with the Dutch Railway Company (NS), Department of Traffic Development.     

Artificial neural net applications in telecommunication systems

The artificial neural net development has had something of a renaissance in the last decade with an impressive range of application areas. From the viewpoint of telecommunication networks and systems, an increasing number of studies can be observed in recent literature dealing with proposed applications of neural nets in telecommunication environments, such as connection admission control in broadband networks, the control of high-speed interconnection networks, channel allocation in cellular mobile systems, adaptive routing, etc. These proposed applications largely use three main neural net classes: feed-forward nets with backpropagation learning, Hopfield feedback nets, and selforganising neural nets. In this paper, we first give an overview of neural net classes and their main properties, and then present a review of applications in telecommunication systems, where attention is devoted to numerical aspects such as the convergence property and learning speed of the proposed neural nets.     

基于工作流网的实时协同系统模拟技术

基于Petri网和工作流的概念，提出一种实时协同系统的形式化模拟与分析技术——逻辑工作流网，逻辑工作流网是抑制弧Petri网和高级Petri网的抽象和扩展，其变迁的输入／输出受逻辑表达式的约束，它与一般工作流网相比，能够在一定程度上缓解状态空间爆炸问题，且便于系统设计人员掌握和使用，该文分析了逻辑工作流网的若干性质及组合网的性质继承问题，并以网上企业销售系统为例，说明逻辑工作流网在实时协同系统模拟分析中的应用。