Catálogo de publicaciones - libros

Network congestion and look-up times are of prime concern in peer-to-peer networks and Gnutella is no exception to this problem. A number of proposals and suggestions have been made to improve the scalability and performance and to reduce the congestion in Gnutella networks. An improvement would be to query a subgroup of positive respondents of the PING message that is exchanged among peers prior to the QUERY message. We discuss possible ways in order to determine “profitable” peers which could result in a successful transfer of a requested file and further highlight issues which we think would reduce congestion in the network.

We describe compiler optimizations for object-based Software Transactional Memory (STM) systems designed to make STM more accessible and efficient than is possible in the context of a purely library-based approach. Current object-based STM libraries are faced with a difficult tradeoff: offer an efficient but complex programming model or, as some recent libraries have done, sacrifice efficiency for ease-of-use. In this paper, we show that this dichotomy is not necessary. Our research suggests that an STM-enabled optimizing compiler can achieve performance comparable to that of the most efficient STM algorithms coded by a programmer, while still supporting a nearly transparent programming model. We also propose novel language extensions to support transactional boosting, a powerful new technique for transforming existing linearizable objects into transactional objects, thus permitting highly concurrent objects such as those found in the java.util.concurrent package to participate in STM transactions. When applied in conjunction with compiler support, we show that transactional boosting is both a flexible and natural way to escape the standard transactional model, and thus offers a promising alternative to existing “expert” approaches, such as open nesting and early release. Based on our results, we conclude that appropriate language support and high quality compiler optimizations are necessary parts of any STM system.

Web Services have become more and more important in these years, and BPEL4WS (BPEL) is a de facto standard for the web service composition and orchestration. It contains several distinct features, including the scope-based compensation and fault handling mechanism.

The denotational semantics and operational semantics have been explored for BPEL. The two approaches should be consistent. This paper considers the unifying of these two semantics. Our approach is to derive the denotational semantics from operational semantics for BPEL, which aims for the consistency of the two models. Moreover, the derivation can be applied in exploring the program equivalence easily, especially for parallel programs.

Using Peer-to-Peer networks is a way to distribute large scale scientific problems. But the P2P networks are very heterogeneous, highly dynamic and volatile. The objective of our work is to offer one P2P network based on high availability. We propose our PHAC framework to improve the dependability of applications. And we present the first results with case computing.

Web forms are commonly used to capture data on the web. With Asynchronous Javascript and XML (Ajax) programming, interactive web forms can be created. However, Ajax programming is complex in a way that the model-view-controller (MVC) code is not clearly separated. This paper discusses about a MVC-oriented web form development called “Webformer” that we develop to simplify and streamline web form development with Ajax. We introduce a scripting language called Web Form Application Language (WebFAL) for modeling web forms. Webformer hides the programming complexity by generating Ajax code directly from the web form models.

Skyline queries, which return the objects that are better than or equal in all dimensions and better in at least one dimension, are useful in many decision making and real-time monitor applications. With the number of dimensions increasing and continuous large volume data arriving, mining the thin skylines over data stream under control of losing quality is a more meaningful problem. In this paper, firstly, we propose a novel concept, called , which uses a skyline object that represents its nearby skyline neighbors within -distance (acceptable difference). Then, two algorithms are developed which prunes the skyline objects within the acceptable difference and adopts correlation coefficient to adjust adaptively thin skyline query quality. Furthermore, our experimental performance study shows that the proposed methods are both efficient and effective.

In composing and using services, user’s requirements are subject to uncertainty and changes. It can be difficult for users to maintain an overview of all available services and to make good choices among them. This paper proposes an approach to proactively recommending suitable services to users. Our major contribution is to have devised a novel user-interest model to describe user’s interests adaptively. A reasonable way is put forward for picking up suitable services timely and its key problem is defined formally. Important properties of the model are theoretically proved, and the effectiveness of recommendations is verified with prototypical implementation and tryouts in public service area.

GridDoc is a Web-based application, which aims to support the instant data integration by end users. This paper presents a service virtualization approach to aggregating Web services into virtual data services, and constructing user-customized data services to support the GridDoc application. Some key mechanisms of the service virtualization, namely the semantics annotation, service aggregation and virtualization operations are discussed. The service virtualization approach has been implemented and its application is illustrated. The paper concludes with a comparative study with other related works.

A domain-specific service registry should satisfy two requirements at least: coping with diverse service description requirements from different services; supporting semantic description on service interfaces for interoperation in a specific domain. This paper proposes an adaptive metadata model that supports flexible semantic description of service interfaces. It uses a simple inheritance mechanism to provide multiple metadata models on a light-weight generic metadata model and semantic annotation templates to facilitate interface semantic description for domain-specific services. The implementation and application of this metadata model in a real-world domain-specific service registry promises that a user can customize a metadata model and add interface semantic metadata in an easy-to-use way.

In this paper globalization is analyzed from the electronic information and communication perspective. Two kinds of communities are distinguished: traditional territorial communities and new kind of content communities. Content communities are the results of human communication via Internet. Content communities group people round a particular information content that is of interest to them. Features of both kinds of communities are analyzed, showing their fundamental differences. Basing on those differences, a conclusion is that global society is a myth, while information society is a reality.