The power of an object type T can be measured as the maximum number n of processes that can solve consensus using only objects of T and registers. This number, denoted cons(T), is called the consensus power of T. This...
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The power of an object type T can be measured as the maximum number n of processes that can solve consensus using only objects of T and registers. This number, denoted cons(T), is called the consensus power of T. This paper addresses the question of the weakest failure detector to solve consensus among a number k > n of processes that communicate using shared objects of a type T with consensus power n. In other words, we seek for a failure detector that is sufficient and necessary to "boost" the consensus power of a type T from n to k. It was shown in Neiger (Proceedings of the 14th annual ACM symposium on principles of distributed computing (PODC), pp. 100-109, 1995) that a certain failure detector, denoted Omega (n) , is sufficient to boost the power of a type T from n to k, and it was conjectured that Omega (n) was also necessary. In this paper, we prove this conjecture for one-shot deterministic types. We first show that, for any one-shot deterministic type T with cons(T) <= n, Omega (n) is necessary to boost the power of T from n to n + 1. Then we go a step further and show that Omega(n) is also the weakest to boost the power of (n + 1)-ported one-shot deterministic types from n to any k > n. Our result generalizes, in a precise sense, the result of the weakest failure detector to solve consensus in asynchronous message-passing systems (Chandra et al. in J ACM 43(4):685-722, 1996). As a corollary, we show that Omega (t) is the weakest failure detector to boost the resilience level of a distributed shared memory system, i.e., to solve consensus among n > t processes using (t - 1)-resilient objects of consensus power t.
Background: With Bio-jETI, we introduce a service platform for interdisciplinary work on biological application domains and illustrate its use in a concrete application concerning statistical data processing in R and ...
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Background: With Bio-jETI, we introduce a service platform for interdisciplinary work on biological application domains and illustrate its use in a concrete application concerning statistical data processing in R and xcms for an LC/MS analysis of FAAH gene knockout. Methods: Bio-jETI uses the jABC environment for service-oriented modeling and design as a graphical process modeling tool and the jETI service integration technology for remote tool execution. Conclusions: As a service definition and provisioning platform, Bio-jETI has the potential to become a core technology in interdisciplinary service orchestration and technology transfer. Domain experts, like biologists not trained in computer science, directly define complex service orchestrations as process models and use efficient and complex bioinformatics tools in a simple and intuitive way.
An almost synchronous stream consists of a sequence of proper messages and pauses transmitted over a directed channel. The paper presents the transformational design of a communicating component which coordinates two ...
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A sequential memory component stores and retrieves data in addressable locations. A fault tolerant implementation suspends read commands to locations without a prior assignment until data becomes available at the requ...
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ISBN:
(纸本)9781604232356
A sequential memory component stores and retrieves data in addressable locations. A fault tolerant implementation suspends read commands to locations without a prior assignment until data becomes available at the requested location. The paper studies the systematic top-down design of a fault tolerant sequential memory component in the setting of stream functions and state transition machines. We formally refine the communication-oriented input/output behaviour into a state-based implementation. The transformation employs a history abstraction function which extracts the component's internal state from the input history. Beyond the particular case study, we explicate generally applicable formal methods for the functional specification and systematic design of interactive components in distributed systems with asynchronous communication.
Modern computer systems are composed of software components which store information and provide services through interfaces. A component-based distributed system evolves by an ongoing interaction [1] between the compo...
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In this paper, we present hybrid testing, a method that combines replay-testing (static testing) with automata learning techniques that generate models of black box systems (dynamic testing). This combination helps br...
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ISBN:
(纸本)9781605580524
In this paper, we present hybrid testing, a method that combines replay-testing (static testing) with automata learning techniques that generate models of black box systems (dynamic testing). This combination helps bridging the gap towards model based testing also for legacy systems. Webtest is an implementation of hybrid testing that builds on top of preexisting technology such as the LearnLib, a framework for automata learning, and the jABC, a framework for modeldriven and service-oriented design, that we use here for modelling, executing, and managing test suites for and models of the web applications under analysis. In particular we intend to move towards Rich Internet Applications (RIAs), that include e.g. advanced client side capabilities and access to heavy resources (e.g. database access) over the Web. Copyright 2008 ACM.
We advocate a new teaching direction for modern CS curricula: extreme model-driven development (XMDD), a new development paradigm designed to continuously involve the customer/application expert throughout the whole s...
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ISBN:
(纸本)9783540884781
We advocate a new teaching direction for modern CS curricula: extreme model-driven development (XMDD), a new development paradigm designed to continuously involve the customer/application expert throughout the whole systems life cycle. Based oil the One-Thing Approach', which works by successively enriching and refining one single artifact, system development becomes in essence a user-centric orchestration of intuitive service functionality. XMDD differs radically from classical software development, which, in our opinion is no longer adequate For the bulk of application programming - in particular when it comes to heterogeneous;cross Organizational systems which must adapt to rapidly changing market requirements. Thus there is a need for new curricula addressing this model-driven, lightweight, quid cooperative development paradigm that puts the user process in the center of the development and the application expert in control of the process evolution.
Web-based access to sensitive and confidential data is realized today via different approaches, using a variety of methods to specify and combine access control policies. In an optic of change management and evolution...
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ISBN:
(纸本)9781605580524
Web-based access to sensitive and confidential data is realized today via different approaches, using a variety of methods to specify and combine access control policies. In an optic of change management and evolution, a structured and flexible model is needed to handle dynamicity, particularly when handling rights in systems with many users which hold different roles. Furthermore the validation of security constraints is an important key to warrant the reliability of control mechanisms. This paper compares the temporal logic-based approach for modeling access control used by the jABC framework with two popular XML-based description languages (XACML and WS-Policy), which are quasi-standards for policy expression in Web applications. Its usage is illustrated here on the example of the web-based Online Conference Service (OCS). The respective functionalities are described and examined in consideration of their ability to validate and enforce the needed policies. Copyright 2008 ACM.
In this paper we show how to apply a tableau-based software composition technique to automatically generate the mediator's service logic. This uses an LTL planning (or configuration) algorithm originally embedded ...
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In this paper we show how to apply a tableau-based software composition technique to automatically generate the mediator's service logic. This uses an LTL planning (or configuration) algorithm originally embedded in the ABC and in the ETI platforms. The algorithm works on the basis of the existing jABC library of available services (SIB library) and of an enhanced description of their semantics given in terms of a taxonomic classification of their behaviour (modules) and abstract interfaces/messages (types).
Extensibility, flexibility, easy maintainability, and long-term robustness are core requirements for modern, highly distributed information and computation systems. Such systems in turn show a steady increase in compl...
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