Yongwang Zhao

An adaptive heuristic approach for distributed QoS-based service composition

QoS-based service selection becomes a commonly accepted procedure to support rapid and dynamic web service composition. In this paper, we study the problem of QoS-based service selection in distributed QoS management environments where QoS values of alternative services are maintained by distributed QoS registries. A distributed heuristic approach is proposed to solve the problem efficiently with a high approximation ratio, and enable adaptability in distributed cross-organization environments with data privacy protection and a low cost of communication. The proposed approach consists of four stages in which variable elimination is used to reduce the size of the problem; constraint decomposition allows performing service selection independently on each QoS registry; supplementary service selection and concentrated optimization improve the approximation ratio. Performance analyses and simulation experiments show that the proposed approach performs efficiently with close-to-optimal results and fits well to distributed QoS management environments.

MIAPS: A web-based system for remotely accessing and presenting medical images

MIAPS (medical image access and presentation system) is a web-based system designed for remotely accessing and presenting DICOM image. MIAPS is accessed with web browser through the Internet. MIAPS provides four features: DICOM image retrieval, maintenance, presentation and output. MIAPS does not intent to replace sophisticated commercial and open source packages, but it provides a web-based solution for teleradiology and medical image sharing. The system has been evaluated by 39 hospitals in China for 10 months.

Medical Image Retrieval with Query-Dependent Feature Fusion Based on One-Class SVM

Due to the huge growth of the World Wide Web, medical images are now available in large numbers in online repositories, and there exists the need to retrieval the images through automatically extracting visual information of the medical images, which is commonly known as content-based image retrieval (CBIR). Since each feature extracted from images just characterizes certain aspect of image content, multiple features are necessarily employed to improve the retrieval performance. Meanwhile, experiments demonstrate that a special feature is not equally important for different image queries. Most of existed feature fusion methods for image retrieval only utilize query independent feature fusion or rely on explicit user weighting. In this paper, we present a novel query dependent feature fusion method for medical image retrieval based on one class support vector machine. Having considered that a special feature is not equally important for different image queries, the proposed query dependent feature fusion method can learn different feature fusion models for different image queries only based on multiply image samples provided by the user, and the learned feature fusion models can re¿ect the different importances of a special feature for different image queries. The experimental results on the IRMA medical image collection demonstrate that the proposed method can improve the retrieval performance effectively and can outperform existed feature fusion methods for image retrieval.

Collaborative Visualization of Large Scale Datasets Using Web Services

Visualization and collaboration of large scale data sets on Internet is still one of biggest challenges in scientific visualization. A distributed, real-time, collaborative system for large scale data like seismic model can be a valuable tool to support scientific research. In this paper, we present a new approach for Web-based synchronized collaborative visualization of large scale data using Web services and rich Web clients which supports collaborative visualization in Web browsers. We use WS-resources in WSRF (Web services resource framework) to maintain states collaborative server. On client side, we design an Ajax-based (asynchronous JavaScript and XML) application using standard Web technologies. A collaborative demonstration of 3D seismic model which is 2GB size is presented and experimental results are showed finally.

Event-based formalization of safety-critical operating system standards: An experience report on ARINC 653 using Event-B

Standards play the key role in safety-critical systems. Errors in standards could mislead system developers understanding and introduce bugs into system implementations. In this paper, we present an Event-B formalization and verification for the ARINC 653 standard, which provides a standardized interface between safety-critical real-time operating systems and application software, as well as a set of functionalities aimed to improve the safety and certification process of such safety-critical systems. The formalization is a complete model of ARINC 653, and provides a necessary foundation for the formal development and verification of ARINC 653 compliant operating systems and applications. Three hidden errors and three cases of incomplete specification were discovered from the verification using the Event-B formal reasoning approach.

An AADL-Based Modeling Method for ARINC653-Based Avionics Software

Avionics software is safe-critical embedded software and its architecture is evolving from traditional federated architectures to Integrated Modular Avionics (IMA) to improve resource usability. ARINC653, as a standard widely employed in the avionics industry, supports partitioning concepts in accordance with the IMA philosophy. To insure the development of the avionics software constructed on ARINC653 operating system with high reliability and efficiency, we propose a model-driven design methodology based on Architecture Analysis &Design Language (AADL) for ARINC653 system. This paper focus on the modeling parts of this methodology which main feature is separating the abstract application function logic represented by AADL Platform-Independent Model (AADL PIM) from the concrete execution architecture represented by AADL Model for ARINC653 (AADL653). Additionally, we provide a refined transformation framework with formally transformation rules to transform AADL PIM to AADL653 automatically and the transformation result model AADL653 can then be used for analysis, verification and code generation.

Towards adaptive web services QoS prediction

Quality of Service (QoS) has been widely used to support dynamic Web Service (WS) selection and composition. Due to the volatile nature of QoS parameters, QoS prediction has been put forward to understand the trend of QoS data volatility and estimate QoS values in dynamic environments. In order to provide adaptive and effective QoS prediction, we propose a WS QoS prediction approach, named WS-QoSP, based on the technique of forecast combination. Different from the existing QoS prediction approaches that choose a most feasible forecasting model and predict relying on this “best” model, WS-QoSP selects multiple potential forecasting models, combines the results of the selected models to optimize the overall forecast accuracy. Results of real data experiments demonstrate the diversified forecast accuracy gains by using WS-QoSP.

A Policy-Based Architecture for Web Services Security Processing

With the development of the Internet, Web Services technology has gradually become the development direction of the e-business, e-government and other fields, and the corresponding security mechanism has received unprecedented attention, while how to design an integrated architecture to enhance web services security remains a problem very difficult to tackle with, and there are no good solutions to support individualized security requirements. As a result of our study we present in this paper a policy-based architecture termed PBA4WSSP for web services security processing. In PBA4WSSP, the processes of all security problems are based on security policy in service stage to enable system security and flexibility. Moreover, this architecture provides the five security services including as integrity, confidentiality, non-repudiation, authentication and authorization. In PBA4WSSP, a web service security module have been designed and implemented.

SEDA4BPEL: A staged event-driven architecture for high-concurrency BPEL engine

Current BPEL engine products are difficult to meet the highly concurrent demands of increasing mission-critical business processes application. We follow the ideas of SEDA and propose a new architecture for high-concurrency BPEL engine, which we call SEDA4BPEL. In SEDA4BPEL, the implementation of BPEL related web services protocols is encapsulated into four primary event-driven stages, to provide independence, isolation and modularity. We also introduce two controllers to manage excessive concurrent process instances. We present the SEDA4BPEL design and the implementation of a BEPL engine based on this architecture. The evaluation results show that SEDA4BPEL applications exhibit high performance and robustness when handling massive concurrency.

Reasoning About Information Flow Security of Separation Kernels with Channel-Based Communication

Assurance of information flow security by formal methods is mandated in security certification of separation kernels. As an industrial standard for separation kernels, ARINC 653 has been complied with by mainstream separation kernels. Security of functionalities defined in ARINC 653 is thus very important for the development and certification of separation kernels. This paper presents the first effort to formally specify and verify separation kernels with ARINC 653 channel-based communication. We provide a reusable formal specification and security proofs for separation kernels in Isabelle/HOL. During reasoning about information flow security, we find some security flaws in the ARINC 653 standard, which can cause information leakage, and fix them in our specification. We also validate the existence of the security flaws in two open-source ARINC 653 compliant separation kernels.