Starts with a brief review of the history and the application areas considered in the literature. The author then proceeds with introductory modeling examples, behavioral and structural properties, three methods of analysis, subclasses of Petri nets and their analysis. In particular, one section is devoted to marked graphs, the concurrent system model most amenable to analysis. Introductory discussions on stochastic nets with their application to performance modeling, and on high-level nets with their application to logic programming, are provided. Also included are recent results on reachability criteria. Suggestions are provided for further reading on many subject areas of Petri nets. >

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Petri nets: Properties, analysis and applications

1. Introduction 2. Background 3. Performance evaluation process algebra 4. Modelling study: multi-server multi-queue systems 5. Notions of equivalence 6. Isomorphism and weak isomorphism 7. Strong bisimilarity 8. Strong equivalence 9. Conclusions Bibliography Index.

/pdf/a-compositional-approach-to-performance-modelling-4ybheka1a7.pdf

A Compositional Approach to Performance Modelling

SPNP, a powerful GSPN package that allows the modeling of complex system behaviors, is presented. Advanced constructs are available in SPNP such as marking-dependent arc multiplicities, enabling functions, arrays of places or transitions, and subnets; the full expressive power of the C programming language is also available to increase the flexibility of the net description. Sophisticated steady-state and transient solvers are available including cumulative and up-to-absorption measures. The user is not limited to a predefined set of measures; detailed expressions reflecting exactly the measures sought can be easily specified. The authors conclude by comparing SPNP with two other SPN-based packages, Great SPN and METASAN. >

SPNP: stochastic Petri net package

The development of techniques for quantitative, model-based evaluation of computer system dependability has a long and rich history. A wide array of model-based evaluation techniques is now available, ranging from combinatorial methods, which are useful for quick, rough-cut analyses, to state-based methods, such as Markov reward models, and detailed, discrete-event simulation. The use of quantitative techniques for security evaluation is much less common, and has typically taken the form of formal analysis of small parts of an overall design, or experimental red team-based approaches. Alone, neither of these approaches is fully satisfactory, and we argue that there is much to be gained through the development of a sound model-based methodology for quantifying the security one can expect from a particular design. In this work, we survey existing model-based techniques for evaluating system dependability, and summarize how they are now being extended to evaluate system security. We find that many techniques from dependability evaluation can be applied in the security domain, but that significant challenges remain, largely due to fundamental differences between the accidental nature of the faults commonly assumed in dependability evaluation, and the intentional, human nature of cyber attacks.

/pdf/model-based-evaluation-from-dependability-to-security-50ybd7tqdv.pdf

Model-based evaluation: from dependability to security

Deadlocks constitute an important issue to be addressed in the design and operation of FMSs. It is shown that prevention and avoidance of FMS deadlocks can be implemented using Petri net models. For deadlock prevention, the reachability graph of a Petri net model of the given FMS is used, whereas for deadlock avoidance, a Petri-net-based online controller is proposed. The modeling of the General Electric FMS at Erie, PA, is discussed. For such real-world systems, deadlock prevention using the reachability graph is not feasible. A generic, Petri-net-based online controller for implementing deadlock avoidance in such real-world FMSs is developed. >

/pdf/deadlock-prevention-and-deadlock-avoidance-in-flexible-42ytodcldx.pdf

Deadlock prevention and deadlock avoidance in flexible manufacturing systems using Petri net models

An Extended Stochastic Petri Net (ESPN) model, useful for modeling systems which exhibit concurrent, asynchronous, or nondeterministic behavior is developed. Applications demonstrating the flexibility of the model for a variety of system modeling applications are presented. Analytic techniques for the representation of a class of ESPNs as Markov or semi-Markov processes are discussed, as in the simulation of more general models. Finally, DEEP (The Duke ESPN Evaluation Package) is previewed.

Extended Stochastic Petri Nets: Applications and Analysis

Current technology allows sufficient redundancy in fault-tolerant computer systems to insure that the failure probability due to exhaustion of spares is low. Consequently, the major cause of failure is the inability to correctly detect, isolate, and reconfigure when faults are present. Reliability estimation tools must be flexible enough to accurately model this critical fault-handling behavior and yet remain computationally tractable. This paper discusses reliability modeling techniques that are based on a behavioral decomposition that provides tractability by separating the reliability model along temporal lines into nearly-disjoint fault-occurrence and fault-handling submodels. An Extended Stochastic Petri Net (ESPN) model provides the needed flexibility for representing the fault-handling behavior, while a non-homogeneous Markov chain accounts for the possibly non-Poisson fault-occurrence behavior. Since the submodels are separate, the ESPN submodel, in which all the time constants are of the same order of magnitude, can be simulated. The non-homogeneous Markov chain is solved analytically, and the result is a hybrid model. The method of coverage factors, used to combine the submodels, is generalized to more accurately reflect the fault-handling effectiveness within the fault-occurrence model. However, errors can still arise in the subsequent reliability predictions due to approximations made in the aggregation of the two submodels and due to inaccurate estimation of component failure rates and other model parameters. The accuracy of the model predictions is evaluated analytically, and error bounds on the system reliability are produced. These modeling techniques have been implemented in the HARP (Hybrid Automated Reliability Predictor) program.

{\bf (Revision of CS-1983-11.)} - Hybrid Reliability Modeling of Fault-Tolerant Computer Systems

We present an effective technique for the combined performance and reliability analysis of multi-mode computer systems. A reward rate (or a performance level) is associated with each mode of operation. The switching between different modes is characterized by a continuous time Markov chain. Different types of service-interruption interactions (as a result of mode switching) are considered. We consider the execution time of a given job on such a system and derive the distribution of its completion time. A useful dual relationship, between the completion time of a given job and the accumulated reward up to a given time, is noted. We demonstrate the use of our technique by means of a simple example.

http://www.dtic.mil/dtic/tr/fulltext/u2/a148444.pdf

S K Trivedi

Papers

Extended Stochastic Petri Nets: Applications and Analysis

{\bf (Revision of CS-1983-11.)} - Hybrid Reliability Modeling of Fault-Tolerant Computer Systems

On Modeling the Performance and Reliability of Multi-Mode Computer Systems