Ontology-Based QoS Aggregation for Composite Web Services

Determining the QoS (quality of service) of composite Web services is of high importance for both service providers and service consumers. Heterogeneity of service descriptions, however, often hinders the aggregation of QoS parameters. We propose ontology-based QoS aggregation that integrates the semantics of QoS parameters and their aggregation into the overall aggregation process. The contribution is a QoS aggregation ontology and a QoS aggregation method that uses this ontology. We demonstrate the usefulness of our proposal for designers of composite services and assess its computational efficiency

QUALITY OF PROCESS ? A BUSINESS PROCESS PERSPECTIVE ON QUALITY OF SERVICE

The fundamental paradigm shift from a product- to a service-oriented economy implies novel technical and organizational challenges. The resulting dynamic of the technical infrastructure and the increasing development towards requesting external business services to be integrated into end-to-end business processes requires mechanisms ensuring the reliability of the organization?s composed services, workflows and business processes. From a business perspective, QoS characteristics defined based on technical services within the infrastructural layer have to be aggregated to more business-relevant Key Performance Indicators on business process layer to express the Quality of Process. These KPIs represent quality that is highly related to the business?s performance (e.g. processing time of a business service) and are crucial for achieving predefined goals in order to stay competitive in the market. The contribution of this paper is threefold: We (i) provide an in-depth requirements analysis for such a holistic quality management framework, we (ii) develop a holistic aggregation framework which enables service level aggregation incorporating the loosely coupled structure of business processes with invoked systems and services in an instance based manner. To demonstrate the expressive power of our framework we (iii) provide an exemplary industrial application scenario and illustrate the functioning and interplay of the designed artifacts

Service adaptation with probabilistic partial models

Web service composition makes use of existing Web services to build complex business processes. Non-functional requirements are crucial for the Web service composition. In order to satisfy non-functional requirements when composing a Web service, one needs to rely on the estimated quality of the component services. However, estimation is seldom accurate especially in the dynamic environment. Hence, we propose a framework, ADFlow, to monitor and adapt the workflow of the Web service composition when necessary to maximize its ability to satisfy the non-functional requirements automatically. To reduce the monitoring overhead, ADFlow relies on asynchronous monitoring. ADFlow has been implemented and the evaluation has shown the effectiveness and efficiency of our approach. Given a composite service, ADFlow achieves 25 %–32 % of average improvement in the conformance of non-functional requirements, and only incurs 1 %–3 % of overhead with respect to the execution time.No Full Tex

INVESTIGATION OF THE ROLE OF SERVICE LEVEL AGREEMENTS IN WEB SERVICE QUALITY

Context/Background: Use of Service Level Agreements (SLAs) is crucial to provide the value added services to consumers to achieve their requirements successfully. SLAs also ensure the expected Quality of Service to consumers. Aim: This study investigates how efficient structural representation and management of SLAs can help to ensure the Quality of Service (QoS) in Web services during Web service composition. Method: Existing specifications and structures for SLAs for Web services do not fully formalize and provide support for different automatic and dynamic behavioral aspects needed for QoS calculation. This study addresses the issues on how to formalize and document the structures of SLAs for better service utilization and improved QoS results. The Service Oriented Architecture (SOA) is extended in this study with addition of an SLAAgent, which helps to automate the QoS calculation using Fuzzy Inference Systems, service discovery, service selection, SLA monitoring and management during service composition with the help of structured SLA documents. Results: The proposed framework improves the ways of how to structure, manage and monitor SLAs during Web service composition to achieve the better Quality of Service effectively and efficiently. Conclusions: To deal with different types of computational requirements the automation of SLAs is a challenge during Web service composition. This study shows the significance of the SLAs for better QoS during composition of services in SOA

Verification of functional and non-functional requirements of web service composition

Abstract. Web services have emerged as an important technology nowadays. There are two kinds of requirements that are crucial to web service composition, which are functional and non-functional requirements. Functional requirements focus on functionality of the composed service, e.g., given a booking service, an example of functional requirements is that a flight ticket with price higher than $2000 will never be purchased. Non-functional requirements are concerned with the quality of service (QoS), e.g., an example of the booking service’s non-functional requirements is that the service will respond to the user within 5 sec-onds. Non-functional requirements are important to web service composition, and are often an important clause in service-level agreements (SLAs). Even though the functional requirements are satisfied, a slow or unreliable service may still not be adopted. In our paper, we propose an automated approach to verify combined functional and non-functional requirements directly based on the semantics of web service composition. Our approach has been implemented and evaluated on the real-world case studies, which demonstrate the effectiveness of our method.

Dealing with Web service QoS factors using constraint hierarchy

Functionality and non-functional properties are two critical factors in web service technology, but non-functional properties (quality factors) are often ignored. Usually, these are articulated as statements of objectives, as opposed to prepositional assertions. A key challenge in dealing with objectives is that there is no obvious means to decide when they are satisfied. In effect, these objectives are never fu lly satisfied, but satisficed to varying degrees. Alternative design decisions need to trade-off varying degrees of satisfaction of potentially mutually contradictory non-functional requirements. In some circumstances, non-Junctional properties are crucial; they do affect the design decision. Upon a request, there are a range o f web services that might provide the required functionality, so the web service selection can only be done based on their Quality of Service (QoS). Therefore, a quality-based web service model is in high demand. The key contribution of this paper is the use of the hierarchical constraint logic programming framework [9, 10] in dealing with quality factors. We show how quality factors can be formulated as soft constraints and how the machinery associated with constraint hierarchies can be used to evaluate the web services