This paper presents a mobile agent approach that aims at satisfying the following requirements of open Internet-based electronic service markets: the mobile agent system should be usable by any Internet user without a...
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(纸本)3540628037
This paper presents a mobile agent approach that aims at satisfying the following requirements of open Internet-based electronic service markets: the mobile agent system should be usable by any Internet user without a need for specifically configurated non-standard software tools. It should reduce costs in mobile computing environments and therefore enhance overall efficiency. It should suit well to an electronic service market where local services are commercially offered and business transactions predominate the interaction between customers and suppliers. As a part of the project OSM (Open Service Model), mobile agents are built on top of two well-established technologies: CORBA and Java. The first is used as a conceptual framework for interoperability, the latter as the programming environment. Since Java does not provide the necessary persistency of execution state, the concept of OSM service profiles is used to embed Java classes and to transfer a coarse-grained execution context in a secure and efficient manner.
In mobile collaborative applications, collaborating agents can move across heterogeneous networks. The collaborating agents also keep changing their roles depending on the work to be performed at that time. I n such s...
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Advances in directory services, caching and replication, and multicasting technologies promise to improve the speed and robustness of the Web's infrastructure. This article examines the technical issues of two imp...
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Advances in directory services, caching and replication, and multicasting technologies promise to improve the speed and robustness of the Web's infrastructure. This article examines the technical issues of two important approaches - Caching and replication.
By integrating the many different technologies and approaches involved in electronic education and commerce, we can effectively support advanced applications in these areas. This paper describes an architecture which ...
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By integrating the many different technologies and approaches involved in electronic education and commerce, we can effectively support advanced applications in these areas. This paper describes an architecture which can be used to facilitate the specification, execution, and distribution of incremental trade documents among heterogeneous interchanges. We argue that the conventional, top-down, centralized approach to workflow, in its current state, is not suitable to support the undetermined nature of an advanced trade application. What this approach lacks is a unified object-oriented model which can be used to design interoperable trading systems with a single set of well-defined abstractions. This paper, in an attempt to overcome the limitations imposed by the conventional approach, presents an overview of principles relating to object interoperability, semantic heterogeneity, and the document-centric paradigm associated with trade documents. A view object model and its relevant components are also discussed.
Parallel programming on loosely coupled distributedsystems is becoming a viable approach with the rapid increase in network speeds and availability of large amounts of unused CPU capacity on individual workstations. ...
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Parallel programming on loosely coupled distributedsystems is becoming a viable approach with the rapid increase in network speeds and availability of large amounts of unused CPU capacity on individual workstations. Parallel programs are often written for a specific configuration of the distributed system such as the number of nodes, their relative speeds and their network connections. These programs perform poorly when there is a change in the configuration or when they are taken to a system other than what they are intended for. We propose a new paradigm which can express the scale of a program as a part of the program itself. The scale of the program is specified in an abstract manner for an arbitrary number of nodes, their relative speeds and their network connections. The runtime system uses this information to decide the actual scale of program on a given distributed system.
In this paper we investigate the efficiency of two solution approaches to infinite stochastic Petri nets: the matrix-geometric method and the spectral expansion method. We first informally present infinite stochastic ...
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In this paper we investigate the efficiency of two solution approaches to infinite stochastic Petri nets: the matrix-geometric method and the spectral expansion method. We first informally present infinite stochastic Petri nets, after which we describe, using uniform notation, the matrix-geometric and the spectral expansion method. We put special emphasis on the numerical aspect of the solution procedures. Then, we investigate the suitability of these approaches to account for batch-movements of tokens. We then compare the two solution approaches when applied to a larger modelling study of a fault-tolerant computer system. It turns out that the spectral expansion method is favorable in all cases, especially when more heavily loaded systems are studied and when batch arrivals are incorporated in the model. To the best of our knowledge, this paper is the first to compare the spectral expansion method, as advocated by Mitrani and Chakka, with the Latouche-Ramaswami algorithm for the matrix-geometric case. Furthermore, our comparisons go well beyond the usual textbook cases, since we are able to generate, with our tool SPN2MGM, models that are much larger than those that have been assessed in the past.
In mobile collaborative applications, collaborating agents can move across heterogeneous networks. The collaborating agents also keep changing their roles depending on the work to be performed at that time. In such si...
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In mobile collaborative applications, collaborating agents can move across heterogeneous networks. The collaborating agents also keep changing their roles depending on the work to be performed at that time. In such situations, a simple and flexible handling of the transition between heterogeneous environments and roles is required. This paper proposes PolyConstraints, a design pattern to handle the generic problem of transitions across multiple network environments and roles.
This report presents a method to collect statistics about unidirectional delays in packet-switched inter- and intranetworks. The necessary synchronization of the computer clocks on source and target host is performed ...
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This report presents a method to collect statistics about unidirectional delays in packet-switched inter- and intranetworks. The necessary synchronization of the computer clocks on source and target host is performed via a new approach that first determines the relative clock drift between these hosts, i.e. the difference in the frequency drifts of the oscillators. This measure is used to adjust the clock timestamps delivered by the target host. Upon synchronization of the clock phases a very accurate time offset between the network hosts can be estimated. Finally, the time-stamps obtained via the exchanged probe packets can be re-evaluated to compute the one-way delays on both transmission paths between the respective hosts.
Comprehensive distributed garbage collection in object-oriented distributedsystems has mostly been addressed via distributed versions of graph-tracing algorithms, a legacy of centralised garbage collection techniques...
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Comprehensive distributed garbage collection in object-oriented distributedsystems has mostly been addressed via distributed versions of graph-tracing algorithms, a legacy of centralised garbage collection techniques. Two features jeopardise the scalability of these approaches: the bottleneck associated with having to reach a global consensus before any resource can actually be reclaimed; and the overhead of eager log-keeping. This paper describes an alternative approach to comprehensive distributed garbage collection that entails computing the vector-time characterising the causal history of some relevant events of the mutator processes computations. Knowing the causal histories of these events makes it possible to identify garbage objects that are not identifiable by means of per-site garbage collection alone. Computing the vector-times necessary to identify garbage is possible without the unbounded space overheads usually associated with dynamically reconstructing vector-times of arbitrary events of distributed computations. Our approach integrates a lazy log-keeping mechanism and therefore tackles both of the aforementioned stumbling blocks of distributed garbage collection.
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