Gurdeep S. Hura

Rule-based design methodology for solving control problems

A rule-based design methodology for solving control problems is presented. For the representation of various constraints, activities, and other dependency properties of the control problem, abstract Petri nets (APNs) which are an extended form of Petri net modeling are used as a specification and formalism tool which can be analyzed using the analysis techniques of Petri-net-based models. The APN provides a compact, consistent, and verifiable description of the dynamic behaviour of the system under consideration in a structured mode. The proposed design methodology supports specification, validation, and analysis through high-level interaction with the modeled system. The various steps which were taken towards the development of such a design paradigm are explained. An example which shows the APN modeling of an elevator system is given. >

Some design aspects of databases through Petri net modeling

The authors exploit the concepts of Petri nets for the modeling of databases through a meaningful interpretation of various database structures. This has been achieved using, specifically, the reachability and conflict concepts of Petri nets. The concept of conflict has been given a mathematical interpretation to suit its applications to database structures. Starting with a network structure, a new class of application for the reachability equation has been proposed. Based upon this, an algorithm has been postulated to access the data paths between any two specified nodes in the database model. The goal is to provide useful data for the design of databases.

Knowledge net shell (KNS): Petri net based development tool for expert systems

Abstract Starting with various design and implementation issues of rule-based expert system, this paper discusses the use of Petri net as an effective and efficient tool for shell based development of expert systems. Petri net approach provides high level interaction with domain expert for automating the construction and maintenance of expert systems. The proposed approach is simple and provides user-friendly environment for query processing and knowledge manipulation.

Determination of all hamiltonian paths and circuits and the minimal feedback set in a graph through Petri nets

Abstract This paper utilizes the reachability concept of Petri nets for the determination of all Hamiltonian paths and circuits and the minimal feedback vertex or edge set in a graph. The proposed technique for the determination of all Hamiltonian paths and all circuits requires only vector additions on the columns of a single matrix as compared to the matrix multiplications required in the existing techniques. This alleviates the computational efforts. Further, the firing characteristics of Petri nets are used for obtaining the minimal feedback vertex or edge set present in a graph. The proposed techniques are simple, applicable to both directed and undirected graphs and are amenable to digital computer implementation.

Abstract Petri net based approach to problem solving in real time applications

A rule based solution for a real time problem based on the abstract Petri net (APN) is provided. The APN provides compact and verifiable models. Certain restrictions, activities, and properties of the elevator system (a representative of a real time problem) are defined by means of a set of behavioral rules to control and manage the functioning of the elevator system. It is shown how these rules can be implemented directly in terms of entities of APN to get the model of the system which will provide an efficient solution. Any additional requirements can also be easily included into the model without affecting the overall structure, thus providing flexibility and modularity for an efficient solution of the problem.<<ETX>>

A tutorial on fault tolerance issues with applications in distributed systems

Abstract Fault tolerance is the ability of a system to perform its function reliably in the presence of faulty hardware or software components. For a system to have this property, many separate issues are involved: fault confinement, fault detection, fault masking, retry, diagnosis, reconfiguration, recovery, restart, repair, and reintegration. These issues are discussed, and are applied to two well-known fault tolerance distributed systems.

Petri net applications: Modeling software, hardware, and other systems with this powerful tool

Modeling computer software, hardware, and other systems using Petri nets is discussed. The various analysis techniques and extension of Petri nets are considered. Problems in Petri net analysis techniques are examined, and analysis techniques that solve them are given.

The role of atomic actions in a distributed system

Abstract Atomic actions play an important role in a distributed enviroment. They may be used as mechanisms to provide process structuring, process synchonization, and fault tolerance, among other functions. This paper discusses the development and definition of an atomic action. Also, identified and described are the properties possessed by atomic actions: indivisibility and recoverability. A theorteical implementation of atomic procedure. Several functions of atomic actions are discussed and implemented.

Synchronization techniques for distributed systems: An overview

Abstract This paper discusses various synchronization mechanisms and primitives which have been introduced for distributed systems and their concurrent programming languages. Distributed systems originated in the need to increase computing power through the technique of breaking a large problem into a number of smaller components (processes), running these smaller processes on separate processors, and recombining their results to solve the original larger problem. The main issues of such techniques are the splitting, interaction and recombining of these smaller processes. Each of these issues has two major components: mutual exclusion and synchronization between resources and/or processes. Generally, synchronization includes the issue of mutual exclusion. This paper provides an overview for individuals who are not overly familiar with distributed systems. The paper will then focus on synchronization primitives, and a few proposed implementations of languages utilizing these primitives.

Extended abstract Petri nets: A constraint-based model of computation

Abstract The aim of this paper is to introduce extended Petri nets (defined as Abstract Petri nets) as a declarative and constraint-based model of computation for providing a design solution for knowledge-based control problems. The control structure of an algorithm can be expressed in an Abstract Petri net-based model. Further, the approach offers flexibility which can be applied in modelling a number of areas of applicability to the overall system during the design phase. The Abstract Petri net-based model (which is based on a relational approach to programming) for constraint programming language systems is structured, and verifiable, and offers high-level interaction and a user-friendly environment to designers/programmers. These concepts and the features of APNs are explained with the help of a suitable example of knowledge-based problems.