Automatic quality of service adaptation for composite web services

Quality of Services (QoS) management has become an important issue for Web services. Indeed, QoS is becoming a crucial and a distinguishing criterion among functionally equivalent Web services. QoS Management consists of two complementary tasks: monitoring and adaptation. Both are very challenging because of the unpredictable and dynamic nature of Web service composition. We are motivated to solve the QoS problem by taking advantage of some characteristics of composite Web services, such as their similarity to traditional workflows. In this thesis, we propose a broker based architecture that enables dynamic QoS monitoring and adaptation for composite Web services. Our approach consists of dynamically changing the execution paths of composed Web services by instrumenting the BPEL process. A new construct flexPath is introduced for supporting alternate execution paths definition in BPEL. We developed a BPEL compiler allowing automatic instrumentation for BPEL definition files. The BPEL process is deployed using the instrumented definition files in order to interact with the QoS broker during execution. The QoS broker is a key component in our architecture and is responsible of monitoring the QoS and managing the adaptation. We propose a broker that enables runtime monitoring of QoS, prediction of potential QoS violation, and the selection of the best execution path of the process in order to improve QoS when needed. We developed a prototype to evaluate our proposed architecture. A case study is also presented through an example BPEL process and a number of partner Web services. The performance of the QoS adaptation has been analyzed and the results showed that the QoS of the BPEL process has been considerably adapted and improved comparing to the original one. In addition, we analyzed the major factors that affect the performance of our prototype tool

A Survey on Service Composition Middleware in Pervasive Environments

The development of pervasive computing has put the light on a challenging problem: how to dynamically compose services in heterogeneous and highly changing environments? We propose a survey that defines the service composition as a sequence of four steps: the translation, the generation, the evaluation, and finally the execution. With this powerful and simple model we describe the major service composition middleware. Then, a classification of these service composition middleware according to pervasive requirements - interoperability, discoverability, adaptability, context awareness, QoS management, security, spontaneous management, and autonomous management - is given. The classification highlights what has been done and what remains to do to develop the service composition in pervasive environments

Proactive SLA negotiation for service based systems: Initial implementation and evaluation experience

This paper describes a framework that we have developed to integrate proactive SLA negotiation with dynamic service discovery to provide cohesive runtime support for both these activities. The proactive negotiation of SLAs as part of service discovery is necessary for reducing the extent of interruptions during the operation of a service based system when the need for replacing services in it arises. The developed framework discovers alternative candidate constituent services for a service client application, and negotiates/agrees but does not activate SLAs with these services until the need for using a service becomes necessary. A prototype tool has been implemented to realize the framework. This prototype is discussed in the paper along with the results of the initial evaluation of the framework

EVEREST IST - 2002 - 00185 : D23 : final report

Deliverable públic del projecte europeu EVERESTThis deliverable constitutes the final report of the project IST-2002-001858 EVEREST. After its successful completion, the project presents this document that firstly summarizes the context, goal and the approach objective of the project. Then it presents a concise summary of the major goals and results, as well as highlights the most valuable lessons derived form the project work. A list of deliverables and publications is included in the annex.Postprint (published version

Dynamic integration of context model constraints in web service processes

Autonomic Web service composition has been a challenging topic for some years. The context in which composition takes places determines essential aspects. A context model can provide meaningful composition information for services process composition. An ontology-based approach for context information integration is the basis of a constraint approach to dynamically integrate context validation into service processes. The dynamic integration of context constraints into an orchestrated service process is a necessary direction to achieve autonomic service composition

The simplicity project: easing the burden of using complex and heterogeneous ICT devices and services

As of today, to exploit the variety of different "services", users need to configure each of their devices by using different procedures and need to explicitly select among heterogeneous access technologies and protocols. In addition to that, users are authenticated and charged by different means. The lack of implicit human computer interaction, context-awareness and standardisation places an enormous burden of complexity on the shoulders of the final users. The IST-Simplicity project aims at leveraging such problems by: i) automatically creating and customizing a user communication space; ii) adapting services to user terminal characteristics and to users preferences; iii) orchestrating network capabilities. The aim of this paper is to present the technical framework of the IST-Simplicity project. This paper is a thorough analysis and qualitative evaluation of the different technologies, standards and works presented in the literature related to the Simplicity system to be developed

Multi-criteria content adaptation service selection broker

In this paper, we propose a service-oriented content adaptation framework and an approach to the Content Adaptation Service Selection (CASS) problem. In particular, the problem is how to assign adaptation tasks (e.g., transcoding, video summarization, etc) together with respective content segments to appropriate adaptation services. Current systems tend to be mostly centralized suffering from single point failures. The proposed algorithm consists of a greedy and single objective assignment function that is constructed on top of an adaptation path tree. The performance of the proposed service selection framework is studied in terms of efficiency of service selection execution under various conditions. The results indicate that the proposed policy performs substantially better than the baseline approach.<br /

QoS-Aware Middleware for Web Services Composition

The paradigmatic shift from a Web of manual interactions to a Web of programmatic interactions driven by Web services is creating unprecedented opportunities for the formation of online Business-to-Business (B2B) collaborations. In particular, the creation of value-added services by composition of existing ones is gaining a significant momentum. Since many available Web services provide overlapping or identical functionality, albeit with different Quality of Service (QoS), a choice needs to be made to determine which services are to participate in a given composite service. This paper presents a middleware platform which addresses the issue of selecting Web services for the purpose of their composition in a way that maximizes user satisfaction expressed as utility functions over QoS attributes, while satisfying the constraints set by the user and by the structure of the composite service. Two selection approaches are described and compared: one based on local (task-level) selection of services and the other based on global allocation of tasks to services using integer programming