1,652 research outputs found

    Systematic composition of distributed objects: Processes and sessions

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    We consider a system with the infrastructure for the creation and interconnection of large numbers of distributed persistent objects. This system is exemplified by the Internet: potentially, every appliance and document on the Internet has both persistent state and the ability to interact with large numbers of other appliances and documents on the Internet. This paper elucidates the characteristics of such a system, and proposes the compositional requirements of its corresponding infrastructure. We explore the problems of specifying, composing, reasoning about and implementing applications in such a system. A specific concern of our research is developing the infrastructure to support structuring distributed applications by using sequential, choice and parallel composition, in the anarchic environment where application compositions may be unforeseeable and interactions may be unknown prior to actually occurring. The structuring concepts discussed are relevant to a wide range of distributed applications; our implementation is illustrated with collaborative Java processes interacting over the Internet, but the methodology provided can be applied independent of specific platforms

    A Peer-to-Peer Middleware Framework for Resilient Persistent Programming

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    The persistent programming systems of the 1980s offered a programming model that integrated computation and long-term storage. In these systems, reliable applications could be engineered without requiring the programmer to write translation code to manage the transfer of data to and from non-volatile storage. More importantly, it simplified the programmer's conceptual model of an application, and avoided the many coherency problems that result from multiple cached copies of the same information. Although technically innovative, persistent languages were not widely adopted, perhaps due in part to their closed-world model. Each persistent store was located on a single host, and there were no flexible mechanisms for communication or transfer of data between separate stores. Here we re-open the work on persistence and combine it with modern peer-to-peer techniques in order to provide support for orthogonal persistence in resilient and potentially long-running distributed applications. Our vision is of an infrastructure within which an application can be developed and distributed with minimal modification, whereupon the application becomes resilient to certain failure modes. If a node, or the connection to it, fails during execution of the application, the objects are re-instantiated from distributed replicas, without their reference holders being aware of the failure. Furthermore, we believe that this can be achieved within a spectrum of application programmer intervention, ranging from minimal to totally prescriptive, as desired. The same mechanisms encompass an orthogonally persistent programming model. We outline our approach to implementing this vision, and describe current progress.Comment: Submitted to EuroSys 200

    CORBA: a middleware for an heterogeneous cooperative system

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    Two kinds of heterogeneities interfere with the integration of different information sources, those in systems and those in semantics. They generate different problems and require different solutions. This paper tries to separate them by proposing the usage of a distinct tool for each one (i.e. CORBA and BLOOM respectively), and analizing how they could collaborate. CORBA offers lots of ways to deal with distributed objects and their potential needs, while BLOOM takes care of the semantic heterogeneities. Therefore, it seems promising to handle the system heterogeneities by wrapping the components of the BLOOM execution architecture into CORBA objects.Postprint (published version

    TIGRA - An architectural style for enterprise application integration

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    Interworking Methodologies for DCOM and CORBA.

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    The DCOM and CORBA standards provide location-transparent access to network-resident software through language independent object interfaces. Although the two standards address similar problems, they do so in incompatible ways: DCOM clients cannot use CORBA objects, and CORBA clients cannot utilize DCOM objects, due to incompatible object system infrastructures. This thesis investigates the performance of bridging tools to resolve the incompatibilities between DCOM and CORBA, in ways that allow clients to cross object system boundaries. Two kinds of tools were constructed and studied: tools that bind clients to services at compile time, and tools that support dynamic client-server bindings. Data developed in the thesis shows that static bridges are on the order of five times faster than dynamic bridges. Measurements conducted with remote clients also showed that with increased network delays, performance differences between static and dynamic bridges become negligible

    Monitoring extensions for component-based distributed software

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    This paper defines a generic class of monitoring extensions to component-based distributed enterprise software. Introducing a monitoring extension to a legacy application system can be very costly. In this paper, we identify the minimum support for application monitoring within the generic components of a distributed system, necessary for rapid development of new monitoring extensions. Furthermore, this paper offers an approach for design and implementation of monitoring extensions at reduced cost. A framework of basic facilities supporting the monitoring extensions is presented. These facilities handle different aspects critical to the monitoring process, such as ordering of the generated monitoring events, decoupling of the application components from the components of the monitoring extensions, delivery of the monitoring events to multiple consumers, etc.\ud The work presented in this paper is being validated in the prototype of a large distributed system, where a specific monitoring extension is built as a tool for debugging and testing the application behaviour.\u

    An approach to building a secure and persistent distributed object management system

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    The Common Object Request Broker Architecture (CORBA) proposed by the Object Management Group (OMG) is a widely accepted standard to provide a system level framework in design and implementation of distributed objects. The core of the Object Management Architecture (OMA) is an Object Request Broker (ORB), which provides transparency of object location, activation, and communications. However, the specification provided by the OMG is not sufficient. For instance, there are no security specifications when handling object requests through the ORBs. The lack of such a security service prevents the use of CORBA from handling sensitive data such as personal and corporate financial information; In view of the above, this thesis identifies, explores, and provides an approach to handling secure objects in a distributed environment along with a persistent object service using the CORBA specification. The research specifically involves the design and implementation of a secured distributed object service. This object service requires a persistent service and object storage for storing and retrieving security specific information. To provide a secure distributed object environment, a secure object service using the specifications provided by the OMG has been designed and implemented. In addition, to preserve the persistence of secure information, an object service has been implemented to provide a persistent data store; The secure object service can provide a framework for handling distributed object in applications requiring security clearance such as distributed banking, online stock tradings, internet shopping, geographic and medical information systems

    A persistent object manager for HEP

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    We propose to perform research in the area of a Persistant Object Manager for HEP. Persistant Objects are those which continue to exist upon process termination and may be accessed by other processes. It is expected that any system based upon this research will work primarily but not necessarily exclusively in an Object Oriented environment. Target applications include follow on or replacement products for existing packages such as GEANT, HEPDB, FATMEN, BHBOOK, experiment specific code event storage. In this respect, it is expected that more functionality will be required than simple persistance. It will be one of the goals of the of the project to define this extra layer of functionality. Strong emphasis will be placed on the use of standards and/or existing solutions wherever possible
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