J.C.A. de Figueiredo

Embedding fault-tolerance properties in the design of complex software systems

Abstract A systematic way to introduce time-dependent and non-time-dependent properties into a component of a complex software system incorporating real-time restrictions is presented. The approach is based on the decomposition of an extended Petri net model, called the G -Net system. The approach to introduce non-time-dependent fault-tolerant properties is based on the analysis of G -Net systems. The idea is to avoid interference in the behavior of a component caused by faulty behavior in a hardware or software component that interacts with it, and also introduce means by which a component can detect a fault in its behavior and prevent itself from generating more errors. Performance analysis based on the introduction of fuzzy time Petri nets is used to define timing constraints. When violated, these timing constraints may trigger the execution of recovery blocks.

A fault tolerant coloured Petri net resource allocation manager for manufacturing systems

We introduce the architecture of an allocation and management system capable to deal with the complexity of flexible manufacturing systems (FMS). We show how to obtain the model of an FMS based on coloured Petri nets (CPN). This model is independent of a specific production trajectory (route), based on CPN. The introduction of fault tolerance in the model of such an allocation and management system is also discussed.

Distributed control of track-vehicle system with fault-tolerant characteristics: a Petri net based approach

In this paper we present a Petri-net-based approach to consider fault tolerance aspects in a modified control track vehicle system. The proposed approach is based on fuzzy time G-nets which is the integration of two Petri nets extensions: fuzzy time Petri net (timing Petri net extension) and G-nets (Petri net extended with object-oriented concepts). We also show how to model such system by means of fuzzy time G-nets.

Towards a multi-agent interactive learning environment oriented to the Petri net domain

This paper focus on results related to the design of a model of a Computer-based Interactive Learning Environment oriented to the Petri net domain, named PN-M. This environment adopt a a multi-agent approach based on a view about the domain knowledge structure as defined in the MATHEMA interactive learning environment. PN-M is focused on problem solving. Hence in this paper we introduce the domain of the problem, that is the design of interlocking Petri models for track vehicle systems.

An object-oriented Petri net modeling tool and abstraction mechanisms for cooperative systems

Groupware systems are inherently concurrent and complex. To formally specify such systems, designers need powerful description tools capable of dealing with concurrency and mechanisms to manage the complexity. In this paper, we present an object-oriented specification language based on Petri nets, and its application to the modeling of a cooperative editor.

An object based Petri net model application to manufacturing systems

With the increasing number and complexity of the resources in computer based systems, e.g, manufacturing systems, it is more and more important to rely on formal methods to model the components of such systems using an object based approach. The motivation to do so is to introduce structuring mechanisms in order to better manage the complexity of such systems. In this work we introduce an object based Petri net with its foundation on coloured Petri nets and G-Nets. G-CPN systems consist of concurrent, cooperating and loose coupling objects, whose main purpose is to deal with the incremental, formal and executable modeling and specifications of complex distributed software systems, encouraging both software reusability and maintenance.

An interactive Petri net tool for modeling, analysis and simulation of complex systems

In this paper we present an interactive tool for complex systems modeling, analysis and simulation using Petri nets and their temporal extensions. The proposed tool is based on user real time interaction and multiprogramming. Three user interactive steps are allowed: editing, analyzing and simulation. To introduce real time user interaction the tool uses a set of functions that allows to edit and simulate temporal behavior of the Petri net, i.e., programmable places, counters, timing and statistical routines. It executes a nonpreemptive round robin escalonator, that uses randomic functions, and implements a real-time executive, consisting in a multiprocessing system. The tool is based on the concepts given by Zhou and Dicesare (1993) for manufacturing systems, that can be used to many kinds of complex systems. Some other properties, as transition firing temporal dependency, resources addition, subtraction, enabling and disabling operations, and deterministic or stochastic task time duration can be used.

Design of distributed track-vehicle systems applying a high-level object oriented Petri net methodology

In this paper, we introduce a Petri net based methodology for the design of a track-vehicle system. The main motivation for the introduction of this methodology is to provide a firm theoretic model to be applied in the development of a system for design automation. We exemplify our presentation by defining the objects for the design of a distributed track vehicle system controller.

Functional verification methodology using Hierarchical Coloured Petri Nets-based testbenches

We present a functional verification methodology that employs hierarchical coloured petri nets (HCPN) to describe the testbench. By this way, we are avoiding the absence of formal techniques concerning the testbench description and keeping a high-level of abstraction that is required in this phase of the project. The hierarchical (de)composition is the solution to deal with large designs. The methodology prescribes a way to (de)compose the testbench that promotes incremental development and reuse of testbench elements. Furthermore, our methodology provides tool support for the testbench creation. Experimental results concerning the functional verification of the MPEG 4 video decoder are presented.

Model checking in object-oriented Petri nets

We present model checking techniques for verifying an object oriented Petri net modeling language (RPOO). Our intention is turn the application of model checking on model-based software development more feasible. In order that we provide means of specifying objects properties regardless Petri nets details. We use Petri nets semantics just to construct the models state space. We present our algorithms to evaluate properties expressed in branching-time temporal logic CTL. We deal with explicit representation of state space emphasizing its OO features. Besides, we remark the results of some applications of our model checker.