A description and analysis of concurrent systems, such as communication systems, whose behavior is dependent on explicit values of time is presented. An enumerative method is proposed in order to exhaustively validate the behavior of P. Merlin's time Petri net model, (1974). This method allows formal verification of time-dependent systems. It is applied to the specification and verification of the alternating bit protocol as a simple illustrative example. >

Modeling and verification of time dependent systems using time Petri nets

A technique is presented for the formal specification and modeling of multimedia composition with respect to intermedia timing. The proposed model is based on the logic of temporal intervals and timed Petri nets. A strategy is evinced for constructing a database schema to facilitate data storage and retrieval of media elements based on the temporal relationship established by the proposed modeling tool. An algorithm which allows the retrieval of media elements from the constructed database in a manner which preserves the temporal requirements of the initial specification is presented. Using the proposed model, the synchronization requirements of complex structures of temporally related objects can be easily specified. >

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Synchronization and storage models for multimedia objects

Petri nets in which random firing delays are associated with transitions whose firing is an atomic operation are known under the name “stochastic Petri nets” These models are discussed, with the purpose of explaining why they were proposed in the performance evaluation field, why random delays with negative exponential probability density functions are mainly used, and what are their strong and weak points An effort is made to summarize the lines of research that are currently being pursued, and to explain what new results would be regarded as breakthroughs and have the most impact on the use of this modeling technique in the application field

Stochastic Petri nets: an elementary introduction

We have developed a Generalized Timed Petri Net (GTPN) model for evaluating the performance of computer systems. Our model is a generalization of the TPN model proposed by Zuberek [1] and extended by Razouk and Phelps [2]. In this paper, we define the GTPN model and present how performance estimates are obtained from the GTPN. We demonstrate the use of our automated GTPN analysis techniques on the dining philosophers example. This example violates restrictions made in the earlier TPN models. Finally, we compare the GTPN to the stochastic Petri net (SPN) models. We show that the GTPN model has capabilities for modeling and analyzing parallel systems lacking in existing SPN models. The GTPN provides an efficient, easily used method of obtaining accurate performance estimates for models of computer systems which include both deterministic and geometric holding times.

A Generalized Timed Petri Net Model for Performance Analysis

The class of Petri nets obtained by eliminating timing from generalized stochastic Petri net (GSPN) models while preserving the qualitative behavior is identified. Structural results for those nets are derived, obtaining the first structural analysis of Petri nets with priority and inhibitor arcs. A revision of the GSPN definition based on the structural properties of the models is presented. It is shown that for a (wide) class of nets, the definition of firing probabilities of conflicting immediate transitions does not require the information on reachable markings. Identification of the class of models for which the net-level specification is possible is also based on the structural analysis results. The procedure for the model specification is illustrated by means of an example. It is also shown that a net-level specification of the model associated with efficient structural analysis techniques can have a substantial impact on model analysis. >

Generalized stochastic Petri nets: a definition at the net level and its implications

Author(s): Razouk, Rami R.; Phelps, Charles V. | Abstract: Petri Nets have been successfully used to model and evaluate the performance of distributed systems. Several researchers have extended the basic Petri Net model to include time, and have demonstrated that restricted classes of Petri Nets can be analyzed efficiently. Unfortunately, the restrictions prohibit the techniques from being applied to many interesting systems, e.g. communication protocols. This paper proposes a version of timed Petri Nets which accurately models communication protocols, and which can be analyzed using Timed Reachability Graphs. Procedures for constructing and analyzing these graphs are presented. The analysis is shown to be applicable to a larger class of Timed Petri Nets than previously thought. The model and the analysis technique are demonstrated using a simple communication protocol.

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Charles V. Phelps

Papers

Performance analysis using timed Petri Nets