This paper presents the development of REF-WS an approach to enable a Web Service provider to reliably evolve their service through the application of refactoring transformations. REF-WS is intended to aid service pro...
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This paper presents the development of REF-WS an approach to enable a Web Service provider to reliably evolve their service through the application of refactoring transformations. REF-WS is intended to aid service providers, particularly in a reliability and performance constrained domain as it permits upgraded 'non-backwards compatible' services to be deployed into a performance constrained network where existing consumers depend on an older version of the service interface. In order for this to be successful, the refactoring and message mediation needs to occur without affecting functional compatibility with the services' consumers, and must operate within the performance overhead expected of the original service, introducing as little latency as possible. Furthermore, compared to a manually programmed solution, the presented approach enables the service developer to apply and parameterize refactorings with a level of confidence that they will not produce an invalid or 'corrupt' transformation of messages. This is achieved through the use of preconditions for the defined refactorings.
Data-centric and service-oriented workflows are commonly used in scientific research to enable the composition and execution of complex analysis on distributed resources. Although there are a plethora of orchestration...
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Testing Web services performance and their Fault Tolerance Mechanisms (FTMs) are crucial for the development of today's applications. Testing the performance and FTMs of composed service systems is hard to measure...
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Testing Web services performance and their Fault Tolerance Mechanisms (FTMs) are crucial for the development of today's applications. Testing the performance and FTMs of composed service systems is hard to measure at design time because service instability is often caused by the nature of the network. Using a real internet environment for testing is difficult to set up and control. We have developed a fault injection toolkit that emulates a WAN within a LAN environment between composed service components and offers full control over the emulated environments in addition to the ability to inject network-related and application specific faults. The tool also generates background workloads on the tested system for producing more realistic results. We describe an experiment that has been carried out to test the impact of fault tolerance protocols deployed at a service client by using our fault injection toolkit.
Compared to the conventional physical cluster, the virtual cluster technology has features such as flexible configuration, easy management and high system security, which provides users with an easily customized compu...
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Compared to the conventional physical cluster, the virtual cluster technology has features such as flexible configuration, easy management and high system security, which provides users with an easily customized computing environment. Virtual machine image files as the most important stored objects in the virtual computing environment include all the information about the whole life cycle of virtual machine. The storage of the virtual machine images is an important part of virtual computing. There are mainly two ways to store the images, which include local storage and networking storage. This paper proposes a mechanism to manage the distributed image files to support the virtual computing environment. It uses the computing nodes` local storage as a chunk server in a distributed file system, and regards the distribution of the image files as a primary factor to choose the computing node to deploy virtual machine and to implement a backup mechanism of distributed images based on historical records of image files. Functional test and performance test results show that it can effectively support the virtual computing environment and has great values of applications and research.
Many recent applications involve processing and analyzing uncertain data. Recently, several research efforts have addressed answering skyline queries efficiently on massive uncertain datasets. However, the research la...
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Many recent applications involve processing and analyzing uncertain data. Recently, several research efforts have addressed answering skyline queries efficiently on massive uncertain datasets. However, the research lacks methods to compute these queries on uncertain data, where each dimension of the uncertain object is represented as an interval or an exact value. In this paper, we extensively study the problem of skyline query on these interval based uncertain objects, which has never been studied before. We first model the problem of querying the skylines on interval datasets. Typically, we address two efficient algorithms with I/O optimal for the conventional interval skyline queries and constrained interval skyline queries, respectively. Extensive experiments demonstrate the efficiency of all our proposed algorithms.
作者：
Kay KlobedanzWolfgang MuellerAchim RettbergC-LAB
Faculty of Electrical Engineering Computer Science and Mathematics University of Paderborn Paderborn Germany Faculty II
Department Computer Science Carl von Ossietzky University슠of슠Oldenburg Oldenburg Germany
In this paper we present an approach for the self reconfiguration of distributed micro-controllers for increased fault tolerance. Based on a modified distributed system topology utilizing a time division multiple acce...
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In this paper we present an approach for the self reconfiguration of distributed micro-controllers for increased fault tolerance. Based on a modified distributed system topology utilizing a time division multiple access (TDMA) protocol, i.e., Flex Ray, we present a self-organized distributed coordinator concept which performs the self-reconfiguration in the case of node failures. We introduce a distributed coordinator, which utilizes redundant slots in the Flex Ray communication schedule and combines messages in configured protocol frames and slots to avoid a complete bus restart. As such, the self-reconfiguration is realized by means of predetermined information about resulting changes in the communication dependencies and (re-)assignments determined in the design phase. To retrieve the necessary information, we present an analytical approach, which determines a combined solution for the initial configuration and all possible reconfigurations for the remaining nodes of the Flex Ray network in case of node failures. Hence, through this method we can design self-reconfiguring network-based systems enabling the handling of node failures for an increased fault tolerance.
As the foundation of cloud computing, Server consolidation allows multiple computer infrastructures running as virtual machines in a single physical node. It improves the utilization of most kinds of resource but memo...
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Long before formation of the Java Community Process, a paper discussing issues of real-time Java and a companion paper proposing a draft API for real-time Java were distributed via a web server hosted by Iowa State Un...
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ISBN:
(纸本)9781450316880
Long before formation of the Java Community Process, a paper discussing issues of real-time Java and a companion paper proposing a draft API for real-time Java were distributed via a web server hosted by Iowa State University [1, 2]. Nearly nine hundred copies of the draft API were downloaded in the first eight months following its release in January 1996. Industry response was overwhelmingly enthusiastic, with multiple real-time operating system companies approaching the author of the papers with offers to fund implementation of the proposed concepts. Ultimately, the author left Iowa State University to found NewMonics, with initial financial backing from an angel investor who helped the company eventually receive more than $15 million of venture capital funding. But the fortunes of real-time Java have not lived up to the promise of the initial enthusiasm. Now, over fifteen years after the initial real-time Java reports were published, and over ten years after initial publication of the real-time Specification for Java (RTSJ) [3], real-time Java is still an oddity within the domains of embedded real-timecomputing. There are only a relatively small number of reported real-time Java success stories. And the only two projects based on the RTSJ have been defense applications, with severe limitations on information about their experience. In the past few years, both IBM and Oracle have backed away from their originally aggressive support for the RTSJ. In recent months, Atego has been approached by an aerospace customer who is requesting access to the technologies described in the original Perc real-time API (PRTAPI) document that had been first published in 1996. A review of that original API document serves to remind the real-time Java community of the ideals that initially attracted such strong industry interest in the promise of real-time Java. This paper describes a possible modern incarnation of the original PRTAPI and discusses why its features are considered pre
Memory management in Safety-Critical Java (SCJ) is based on time bounded, non garbage collected scoped memory regions used to store temporary objects. Scoped memory regions may have different life times during the exe...
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Memory management in Safety-Critical Java (SCJ) is based on time bounded, non garbage collected scoped memory regions used to store temporary objects. Scoped memory regions may have different life times during the execution of a program and hence, to avoid leaving dangling pointers, it is necessary to check that reference assignments are performed only from objects in shorter lived scopes to objects in longer lived scopes (or between objects in the same scoped memory area). SCJ offers, compared to the RTSJ, a simplified memory model where only the immortal and mission memory scoped areas are shared between threads and any other scoped region is thread private. In this paper we present how, due to this simplified model, a single scope nesting level can be used to check the legality of every reference assignment. We also show that with simple hardware extensions a processor can see some improvement in terms of execution time for applications where cross-scope references are frequent. Our proposal was implemented and tested on the Java Optimized Processor (JOP).
Agent-based modeling and simulation is a way to model the behavior of populations of components and their interactions within a system. The key of this approach is to model the components of the system as autonomous a...
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