Generalized Stochastic Petri Nets Models Research Articles

An Evaluation Framework for Comparative Analysis of Generalized Stochastic Petri Net Simulation Techniques

Availability of a common, shared benchmark to provide repeatable, quantifiable, and comparable results is an added value for any scientific community. International consortia provide benchmarks in a wide range of domains, being normally used by industry, vendors, and researchers for evaluating their software products. In this regard, a benchmark of untimed Petri net models was developed to be used in a yearly software competition driven by the Petri net community. However, to the best of our knowledge there is not a similar benchmark to evaluate solution techniques for Petri nets with timing extensions. In this paper, we propose an evaluation framework for the comparative analysis of generalized stochastic Petri nets (GSPNs) simulation techniques. Although we focus on simulation techniques, our framework provides a baseline for a comparative analysis of different GSPN solvers (e.g., simulators, numerical solvers, or other techniques). The evaluation framework encompasses a set of 50 GSPN models including test cases and case studies from the literature, and a set of evaluation guidelines for the comparative analysis. In order to show the applicability of the proposed framework, we carry out a comparative analysis of steady-state simulators implemented in three academic software tools, namely, GreatSPN , PeabraiN , and TimeNET . The results allow us to validate the trustfulness of these academic software tools, as well as to point out potential problems and algorithmic optimization opportunities.

Modeling and Performance Evaluation of Multistage Serial Manufacturing Systems with Rework Loops and Product Polymorphism

This paper studies multistage serial manufacturing systems with the integrated consideration of machine failures, process defects, multiple rework loops, etc. In particular, multiple rework loops and product polymorphism lead to a more complex conversion of internal material flows, and therefore it's difficult to model and analyse such manufacturing systems. A modular modeling method based on Generalized Stochastic Petri Nets (GSPN) is presented to characterize the material flows, it is capable of representing the processing differences resulting from product polymorphism comparing with traditional Markov model or Queuing network model. By analysing the model, the processing ratio of each workstation is inferred. Using 2M1B (two-machine and one-buffer) Markov cell model as the building blocks, which is obtained based on the GSPN models for their isomorphism, an overlapping decomposition method is then developed for evaluating the performance of the multistage serial systems with rework loops. Numerical experiments and a case study of a powertrain assembly line illustrate the efficiency of the proposed method.

GSPN-Based Analysis of Storage Infrastructures for Rendering System

By taking transmission delay into account, the optimization of distributed rendering environment (DRE) was concerned in this paper. Considering distributed animation rendering environment as the object of study, two Generalized Stochastic Petri Nets (GSPN) models for “completely distributed storage” infrastructure (CDSI) and “hybrid distributed storage” one (HDSI) were constructed respectively. Moreover, by choosing average time delay as the performance index, analysis was conducted by applying the equivalent formulas for solving Stochastic Petri Nets (SPN) models of serial and parallel types to these two GSPN models. Based on comparison of such models’ numerical simulation results, conclusion on these two infrastructures’ advantages and disadvantages is deprived thereby. It offers important quantitative foundations for choosing appropriate storage schemes and scheduling algorithms.

Distributed Response Time Analysis of GSPN Models with MapReduce

Generalized stochastic Petri nets (GSPNs) are widely used in the performance analysis of computer and communications systems. Response time densities and quantiles are often key outputs of such analysis. These can be extracted from a GSPN’s underlying semi-Markov process using a method based on numerical Laplace transform inversion. This method typically requires the solution of thousands of systems of complex linear equations, each of rank n, where n is the number of states in the model. For large models substantial processing power is needed and the computation must therefore be distributed. In this paper we describe the implementation of a response time analysis module for the Platform Independent Petri net Editor (PIPE2) which interfaces with Hadoop, an open-source implementation of Google’s MapReduce distributed programming environment, to provide distributed calculation of response time densities in GSPN models. The software is validated with results calculated analytically as well as simulated results for larger models. Excellent scalability is shown.

Performance Evaluation of Workflows Using Continuous Petri Nets with Interval Firing Speeds

In this paper, we study performance evaluation of workflow-based information systems. Because of state space explosion, analysis by stochastic models, such as stochastic Petri nets and queuing models, is not suitable for workflow systems in which a large number of flow instances run concurrently. We use fluid-flow approximation technique to overcome this difficulty. In the proposed method, GSPN (Generalized Stochastic Petri Nets) models representing workflows are approximated by a class of timed continuous Petri nets, called routing timed continuous Petri nets (RTCPN). In RTCPN models, each discrete set is approximated by a continuous region on a real-valued vector space, and variance in probability distribution is replaced with a real-valued interval. Next we derive piecewise linear systems from RTCPN models, and use interval methods to compute guaranteed enclosures for state variables. As a case study, we solve an optimal resource assignment problem for a paper review process.

An Empirical Performance Study on PSIM

It is well known that errors caught in the early stages of system development life cycle greatly helped reduce the expense for later error fixing and mitigate risks and complications. Performance analysis is one of the methods to ensure satisfactory system performance that can avoid redesign and patch in the later stage of system development when performance problems emerge. Much work has been done to address such concerns collectively known as the ‘performance engineering’ problem. However, a comprehensive method is still needed to provide an end-to-end support for performance evaluation on software architecture design. Automated tools to support the method must be developed, and its validation must be carefully planned and conducted. In response to this need, we propose our approach, PSIM (performance simulation and modeling). PSIM is a performance simulation and modeling tool that integrated performance properties into software architecture specifications expressed in several major UML diagrams. PSIM models can be transformed into Colored GSPN (colored generalized stochastic Petri nets) via an automated tool. As a result, the Colored GSPN models can be simulated to perform model-based performance evaluation. In this paper PSIM is first briefly reviewed and illustrated through modeling a web-based electronic conferencing system, called M-Net, to derive performance metrics. We then conduct runtime performance testing to the implementation of M-Net and compare the simulation results against the runtime testing data. PSIM is shown to be effective in predicting system performance and in identifying system performance bottlenecks through this experimentation.

High Assurance Software Systems

The last few decades are marked by an unprecedented increase in the complexity and consequence of information technology systems. High assurance software systems must satisfy basic functional service properties that the system intends to deliver, as well as guarantee desirable system properties such as security, safety, timeliness and reliability. Examples of high assurance software systems include command and control systems, nuclear power plants, electronic banking, aerospace systems, automated manufacturing and medical systems. One of the major challenges in high assurance software engineering is to develop well-founded methods for system construction, verification and validation, so they provide critical services with a high degree of confidence in their correctness and quality. The goal of the special issue is to bring together innovative research ideas and advances in the field of high assurance software systems to address these challenges. To this end, the guest editors invited six papers published in the 29th IEEE Annual International Computer Software and Applications Conference (COMPSAC 2005) in the conference theme of High Assurance Software Systems to submit to this special issue, from which four papers after a rigorous review process have been selected to appear in the special issue. In their paper ‘An Empirical Performance Study on PSIM’, Jinchun Xia, Carl K. Chang, Jeff Wise and Yujia Ge [1] address performance evaluation of software architecture designs. They describe a PSIM (Performance SImulation and Modeling) tool that integrates performance properties into software architecture specifications expressed in UML syntax. PSIM models can be transformed into Colored GSPN (Colored Generalized Stochastic Petri nets) via an automated tool. As a result, the Colored GSPN models can be simulated to perform model-based performance evaluation. PSIM is shown to be effective in predicting system performance and identifying system performance bottlenecks to address the timeliness property of high assurance software systems early in the development lifecycle. High assurance mobile computing systems often have fault tolerance and timeliness requirements which exceed those encountered in conventional distributed systems. The second paper ‘Design and Evaluation of a Low-Latency Checkpointing Scheme for Mobile Computing Systems’ by Guohui Li and Lihchyun Shu [2] presents a coordinated checkpointing scheme which reduces the latency in global checkpointing for failure recovery of high assurance mobile systems. The method proposed significantly reduces the latency associated with checkpoint request propagation. Experimental results indicate that an improvement of up to a 60% reduction in latency can be achieved with <2% extra overhead incurred during runtime to provide timely failure recovery for high assurance mobile systems. The third paper ‘A Blocking-Based Approach to Protocol Validation’ by Qizhi Ye, Yu Lei and David Kung [3] reports a new analysis method for protocol validation. Their method, based on reachability analysis, guarantees to detect protocol logical errors including deadlocks, unspecified receptions and channel overflows prior to actual system deployment. The authors apply the analysis method to 160 synthesized protocols as well as two real protocols to demonstrate its applicability to high assurance software systems that rely on these protocols. Its performance is especially sound when the non-blocking ratio of a protocol is high. Phishing is a form of online identity theft that aims to steal sensitive information such as online banking passwords and credit card information from users. The last paper ‘Protecting Users against Phishing Attacks’ by Engin Kirda and Christopher Kruegel [4] presents a novel method that protects users against spoofed web-based phishing attacks. Their tool called AntiPhish tracks the sensitive information of a user and generates warnings whenever the user attempts to transmit this information to a website that is considered untrusted. AntiPhish is a step in the right direction for protecting software systems against spoofed website-based phishing attacks. We would like to thank the reviewers for their superb work of refereeing and improving the quality as well as the presentation of the four papers selected in this special issue.

On the performance analysis of ABR in ATM LANs with Stochastic Petri Nets

In this paper we use Generalized Stochastic Petri Nets (GSPNs) and Stochastic Well-formed Nets (SWNs) for the performance analysis of Asynchronous Transfer Mode (ATM) Local Area Networks (LANs) that adopt the Available Bit Rate (ABR) service category in its Relative Rate Marking (RRM) version. We also consider a peculiar version of RRM ABR called Stop & Go ABR; this is a simplified ABR algorithm designed for the provision of best-effort services in low-cost ATM LANs, according to which sources can transmit only at two different cell rates, the Peak Cell Rate (PCR) and Minimum Cell Rate (MCR). Results obtained from the solution of GSPN models of simple ATM LAN setups comprising RRM or Stop & Go ABR users, as well as Unspecified Bit Rate (UBR) users, are first validated through detailed simulations, and then used to show that Stop & Go ABR is capable of providing good performance and fairness in a number of different LAN configurations. We also develop SWN models of homogeneous ABR LANs, that efficiently and automatically exploit system symmetries allowing the investigation of larger LAN configurations.

A Distributed Algorithm for GSPN Reachability Graph Generation

The applicability of generalized stochastic Petri nets (GSPNs) and other high-level modeling formalisms to real systems is often constrained by the explosion in the size of the underlying state-space representation. This paper describes a distributed program taking advantage of the large amount of memory and powerful computational resources of distributed computing systems to enable the construction of large state-space graphs generated by GSPN models. High state-space cardinalities and significant speedup with respect to sequential techniques are achieved by means of state space partitioning based on a distributed hashing function. The main algorithmic characteristics (global and local hashing and buffering of messages) are analyzed in detail and their effects are assessed by means of performance measurements on a PC cluster and a Cray T3D parallel machine. Performance results emphasize the good scalability with the number of processors of the proposed approach, even without fast interconnection networks. While the distributed reachability graph construction technique has been conceived for GSPN solution, the issues raised are relevant to other modeling systems whose common trait is the generation of state spaces with irregular and a priori unknown structure.

GSPN models of bridged LAN configurations

Communication systems comprising several local area networks (LANs) interconnected by bridges are modeled with Generalized Stochastic Petri Nets (GSPNs). GSPN models are developed at different levels of detail, progressively abstracting from the detailed behavior of real systems, and exploiting symmetries present in simple interconnected LAN topologies by “folding” the detailed GSPN models. The numerical results obtained from the solution of GSPN models are validated against results of very detailed simulation experiments, and found in good agreement, even for the most abstract GSPN models. Advantages and drawbacks of the GSPN modeling approach are discussed at the end of the paper.

Modeling ATM systems with GSPNs and SWNs

This paper overviews the work of the authors in the field of modeling and analysis of Asynchronous Transfer Mode (ATM) networks using Generalized Stochastic Petri Nets (GSPN) and a special class of high-level stochastic Petri nets known as Stochastic Well-formed Nets (SWN). These formalisms are first shown to be adequate tools for the development of models of ATM systems, provided that only one timed transition is used, together with many immediate transitions. The only timed transition in the GSPN and SWN models represents the ATM systems cell time, while immediate transitions implement the ATM systems behavior. The firing time distribution of the only timed transition is irrelevant for the computation of several interesting performance indices. The results, as well as the problems, derived from the analysis of ATM switches and Local Area Networks (LAN) that adopt the Available Bit Rate (ABR) service category are summarized and discussed, providing references to the works containing the technical details.

Automated construction of GSPN models for flexible manufacturing systems

Generalized stochastic Petri nets (GSPNs) are often used to specify flexible manufacturing systems (FMSs) and their control systems. While GSPNs are a powerful tool for system modeling, their complexity can become unmanageable for all but the simplest `toy' systems. Thus, manual construction of GSPNs can quickly become unacceptably slow and error-prone. In this paper, a formal method is developed to automatically construct a GSPN model for a given FMS. An FMS description language (FMSDL) is presented as the language for the input file of a GSPN construction program named FMSPet. FMSPet translates FMSDL input files into a GSPN system model, maps the specified process plans onto the given physical system, and attaches control stubs to resolve conflicts. The output GSPN is formatted as an input file for the stochastic Petri net package (SPNP) to support the analysis and evaluation of the structural and temporal properties of the net.

Dependability modeling using Petri-nets

This paper describes a methodology to construct dependability models using generalized stochastic Petri nets (GSPN) and stochastic reward nets (SRN). Algorithms are provided to convert a fault tree (a commonly used combinatorial model type) model into equivalent GSPN and SRN models. In a fault-tree model, various kinds of distributions can be assigned to components such as defective failure-time distribution, nondefective failure-time distribution, or a failure probability. The paper describes subnet constructions for each of these different cases, and shows how to incorporate repair in these models. >

Use of GSPNs for concurrent software validation in EPOCA

The main issues related to the use of the Generalized Stochastic Petri Nets (GSPN) formalism for computer supported concurrent software comprehension and validation are discussed. A GSPN-based approach is currently under investigation in the EPOCA Project, based on the integration of the DIStributed C development system with the GreatSPN tool for editing and analysis of GSPN models.

Understanding parallel program behavior through petri net models

Generalized stochastic Petri nets (GSPN) are proposed in this paper as a way to represent and analyze programs written with process-oriented parallel languages. Following an approach that has already been proposed in the literature, parallel programs are translated into GSPN models that are used to perform a static analysis yielding information on possible deadlocks, mutual exclusion, and resource utilization. These models offer help in understanding the overall behavior of a parallel program, increase confidence in its correctness, and permit assessment of the efficiency of its implementation. The feasibility of automatic generation of Petri nets from program code is discussed and the problem of correctly modeling communications and flow control variables is addressed.

Applying generalized stochastic Petri nets to manufacturing systems containing nonexponential transition functions

Generalized stochastic Petri nets (GSPNs) are applied to flexible manufacturing systems (FMSs). Throughput subnets and s-transitions are presented. Two FMS examples containing nonexponential distributions, which were analyzed in previous papers by queuing theory and probability theory respectively, are treated using GSPNs developed using throughput subnets and s-transitions. The GSPN results agree with the previous results, and developing and analyzing the GSPN models are straightforward and relatively easy compared to other methodologies. >