41,527 research outputs found

    A comparative study of structured and un-structured remote data access in distributed computing systems

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    Recently, the use of distributed computing systems has been growing rapidly due to the result of cheap and advanced microelectronic technology. In addition to the decrease in hardware costs, the tremendous development in machine to machine communication interfaces, especially in local area networking, also favours the use of distributed systems. Distributed systems often require remote access to data stored at different sites. Generally, two models of access to remote data storage exist: the un structured and structured models. In the former, data is simply stored as row of bytes, whereas in the latter, data is stored along with the associated access codes. The objective of this thesis is to compare these two models and hence determines the tradeoffs of each model. First of all, an extended review of the field of distributed data access is provided which addressing key issues such as the basic design principles of distributed computing systems, the notions of abstract data types, data inheritance, data type system and data persistence. Secondly, a distributed system is implemented using the persistent programming language PS-algol and the high level language C in conjunction with the remote procedure call facilities available in Unix(^1) 4.2 BSD operating system. This distributed system makes extensive use of Unix's software tools and hence it is called DCSUNIX for Distributed Computing System on UNIX. Thirdly, two specific applications which employ the implemented system will be given so that a comparison can be made between the two remote data access models mentioned above. Finally, the implemented system is compared with the criteria established earlier in the thesis. keywords: abstract data types, class, database management, data persistence, information hiding, inheritance, object oriented programming, programming languages, remote procedure calls, transparency, and type checking

    Object-oriented Tools for Distributed Computing

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    Distributed computing systems are proliferating, owing to the availability of powerful, affordable microcomputers and inexpensive communication networks. A critical problem in developing such systems is getting application programs to interact with one another across a computer network. Remote interprogram connectivity is particularly challenging across heterogeneous environments, where applications run on different kinds of computers and operating systems. NetWorks! (trademark) is an innovative software product that provides an object-oriented messaging solution to these problems. This paper describes the design and functionality of NetWorks! and illustrates how it is being used to build complex distributed applications for NASA and in the commercial sector

    A metaobject architecture for fault-tolerant distributed systems : the FRIENDS approach

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    The FRIENDS system developed at LAAS-CNRS is a metalevel architecture providing libraries of metaobjects for fault tolerance, secure communication, and group-based distributed applications. The use of metaobjects provides a nice separation of concerns between mechanisms and applications. Metaobjects can be used transparently by applications and can be composed according to the needs of a given application, a given architecture, and its underlying properties. In FRIENDS, metaobjects are used recursively to add new properties to applications. They are designed using an object oriented design method and implemented on top of basic system services. This paper describes the FRIENDS software-based architecture, the object-oriented development of metaobjects, the experiments that we have done, and summarizes the advantages and drawbacks of a metaobject approach for building fault-tolerant system

    Implementing fault tolerant applications using reflective object-oriented programming

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    Abstract: Shows how reflection and object-oriented programming can be used to ease the implementation of classical fault tolerance mechanisms in distributed applications. When the underlying runtime system does not provide fault tolerance transparently, classical approaches to implementing fault tolerance mechanisms often imply mixing functional programming with non-functional programming (e.g. error processing mechanisms). The use of reflection improves the transparency of fault tolerance mechanisms to the programmer and more generally provides a clearer separation between functional and non-functional programming. The implementations of some classical replication techniques using a reflective approach are presented in detail and illustrated by several examples, which have been prototyped on a network of Unix workstations. Lessons learnt from our experiments are drawn and future work is discussed

    Service-Oriented Architecture for Space Exploration Robotic Rover Systems

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    Currently, industrial sectors are transforming their business processes into e-services and component-based architectures to build flexible, robust, and scalable systems, and reduce integration-related maintenance and development costs. Robotics is yet another promising and fast-growing industry that deals with the creation of machines that operate in an autonomous fashion and serve for various applications including space exploration, weaponry, laboratory research, and manufacturing. It is in space exploration that the most common type of robots is the planetary rover which moves across the surface of a planet and conducts a thorough geological study of the celestial surface. This type of rover system is still ad-hoc in that it incorporates its software into its core hardware making the whole system cohesive, tightly-coupled, more susceptible to shortcomings, less flexible, hard to be scaled and maintained, and impossible to be adapted to other purposes. This paper proposes a service-oriented architecture for space exploration robotic rover systems made out of loosely-coupled and distributed web services. The proposed architecture consists of three elementary tiers: the client tier that corresponds to the actual rover; the server tier that corresponds to the web services; and the middleware tier that corresponds to an Enterprise Service Bus which promotes interoperability between the interconnected entities. The niche of this architecture is that rover's software components are decoupled and isolated from the rover's body and possibly deployed at a distant location. A service-oriented architecture promotes integrate-ability, scalability, reusability, maintainability, and interoperability for client-to-server communication.Comment: LACSC - Lebanese Association for Computational Sciences, http://www.lacsc.org/; International Journal of Science & Emerging Technologies (IJSET), Vol. 3, No. 2, February 201

    Mentat: An object-oriented macro data flow system

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    Mentat, an object-oriented macro data flow system designed to facilitate parallelism in distributed systems, is presented. The macro data flow model is a model of computation similar to the data flow model with two principal differences: the computational complexity of the actors is much greater than in traditional data flow systems, and there are persistent actors that maintain state information between executions. Mentat is a system that combines the object-oriented programming paradigm and the macro data flow model of computation. Mentat programs use a dynamic structure called a future list to represent the future of computations

    EOS: A project to investigate the design and construction of real-time distributed embedded operating systems

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    The EOS project is investigating the design and construction of a family of real-time distributed embedded operating systems for reliable, distributed aerospace applications. Using the real-time programming techniques developed in co-operation with NASA in earlier research, the project staff is building a kernel for a multiple processor networked system. The first six months of the grant included a study of scheduling in an object-oriented system, the design philosophy of the kernel, and the architectural overview of the operating system. In this report, the operating system and kernel concepts are described. An environment for the experiments has been built and several of the key concepts of the system have been prototyped. The kernel and operating system is intended to support future experimental studies in multiprocessing, load-balancing, routing, software fault-tolerance, distributed data base design, and real-time processing
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