• Journal of the Korea Society of Computer and Information
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• v.14 no.4
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• pp.77-86
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• 2009

At present, Web services become main means to construct web applications. As the number of web services grows and various kind of web services have been produced, QoS properties of web services are one of important criteria to select more appropriate web services. However, the selected web services may become inappropriate for the Requester's requirements, because QoS is kind of dynamic properties. this paper proposes a framework that proposed that finds an appropriate web service for Requester's QoS requirements, and dynamically replaces an inappropriate web service with right one. The problems which happen in substitution step are also identified and the solutions are described with an illustrative example.

• Proceedings of the Korea Society for Simulation Conference
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• 2005.11a
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• pp.39-44
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• 2005

최근 웹 서비스(Web Service)와 웹 프로세스(Web Process)는 이기종 시스템의 통합과 웹 애플리케이션 배포를 위한 대안으로 주목받고 있으며, 이에 따라 웹 서비스의 QoS(Quality of Services)의 중요성도 증가하고 있다. 본 논문에서는 웹 서비스의 QoS 분석 방법을 제안하고, QoS 중심의 웹 서비스 조합 도구인 SimQom4W (Simulation-based QoS-aware Composer for Web Services)를 소개한다. SimQom4W는 첫째, 웹 서비스와 웹 프로세스의 구성을 시각으로 기술하고, 둘째, 웹 프로세스에 대한 테스트 코드와 시뮬레이션 코드를 자동 생성하여 실행시킴으로써 QoS를 분석한다. 셋째, 다양한 QoS 요구사항을 만족하는 최적의 웹 프로세스를 선택할 수 있도록 하며, 넷째, 웹 서비스의 QoS 분석 및 평가 데이터의 보고서를 생성하여 제공한다.

• The Journal of Society for e-Business Studies
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• v.14 no.4
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• pp.149-166
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• 2009

With the rapid development of Web Service technology, the number of Web Service providers which provide same Web Services are increasing. As a result, the QoS elements become more and more important factors for Web Service matchmaking. But, most of previous research efforts do not consider various QoS elements including Service-specific QoS elements during the matchmaking process. In this paper, we propose a Web Service matchmaking scheme which allow dynamic QoS adaptation using the RSS technique. We first classify various QoS elements and describe an extensible QoS model. We then explain a matchmaking scheme, which can utilize the proposed QoS elements. We also show how to dynamically add user-specific QoS elements using the RSS mechanism, thus improving the correctness of web service matchmaking process. Finally, we implemented the proposed schemes and showed the usefulness of our methods through some experiments.

• Journal of the Korea Society of Computer and Information
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• v.16 no.2
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• pp.243-248
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• 2011

According to increasing of accessing multimedia stream contents, Web services have become popular. However, these Web services are not supported with the same quality to Web clients who frequently access multimedia services. This paper proposes ontological technique to apply client level Quality of Service(QoS) that provides two different levels to serve Web service with proper quality by contribution value. And, it describes with UML(Unified Modeling Language) how to relate QoS and SLA(Service Level Agreement). Main contribution of this paper is to support client level QoS and SLA and to use Ontology for it. Therefore, this work uses an ontology-based approach to organize QoS and SLA, enabling semantic classification of all Web services based on domains and QoS and SLA attributes.

• The KIPS Transactions:PartD
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• v.19D no.4
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• pp.299-306
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• 2012

To fulfill the complex user requirement, composition web service comprised of existing services is considered from the efficient and reusable point of view instead of making entirely new web service. However, with the growing the number of web services which provide the same functionality but differ in quality value, the service composition becomes a decision problem on which component services should be selected such that end-to-end QoS constraints by the client and overall QoS of the composition service are satisfied. QoS of service aspects is a determinant factor for selecting the services, since the performance of the composed service is determined by the performance of the involved component web service. In this paper, hybrid genetic algorithm is presented to select component services to take part in the QoS-aware composition. The local search method is used to be combined with the genetic algorithm to improve the individuals (component service) in population as well as composed service. The paper also presents a set of experiments conducted to evaluate the efficiency of selection algorithm using the real web service data.

• Journal of the Korea Society of Computer and Information
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• v.19 no.12
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• pp.209-218
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• 2014

The more mobile devices consuming web services, the more QoS-aware selection of mobile web services, we need. A QoS(Quality of Service) contract is an agreement between the web service provider and the mobile user that specifies the level of the service quality. Web services users can be assured of the level of the service quality specified by the QoS contract. We propose a broker-based framework for QoS-aware mobile web services selection in this work. Under this architecture, the mobile users can request the web services through the service broker on the wireless networks. The service broker utilizes agents to monitor the web services quality and manages the service quality by notifying the service provider and mobile user of the service contract violation. Reliability, response time, and cost were the metrics used for QoS monitoring. Futhermore mobile users can select a web service best suited for his/her needs through the service broker.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.3
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• pp.971-989
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• 2015

With the development of cloud computing, more and more Web services are deployed on geo-distributed datacenters and are offered to cloud users all over the world. Through service composition technologies, these independent fine-grain services can be integrated to value-added coarse-grain services. During the composition, a number of Web services may provide the same function but differ in performance. In addition, the distribution of cloud datacenters presents a geographically dispersive manner, which elevates the impact of the network on the QoS of composite services. So it is important to select an optimal composition path in terms of QoS when many functionally equivalent services are available. To achieve this objective, we first present a graph model that takes both QoS of Web services and QoS of network into consideration. Then, a novel approach aiming at selecting the optimal composition path that fulfills the user's end-to-end QoS requirements is provided. We evaluate our approach through simulation and compare our method with existing solutions. Results show that our approach significantly outperforms existing solutions in terms of optimality and scalability.

• Journal of KIISE:Software and Applications
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• v.34 no.5
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• pp.431-446
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• 2007

Executable composite Web services are selected by binding a given abstract workflow with the specific Web services that satisfy given QoS requirements. Considering the rapidly increasing number of Web services and their highly dynamic QoS environment, the fast selection of composite services is important. This paper presents a method for quality driven comosite Web services selection based on a workflow partition strategy. The proposed method partitions an abstract workflow into two sub-workflows to decrease the number of candidate services that should be considered. The QoS requirement is also decomposed for each partitioned workflow. Since the decomposition of a QoS requirement is based on heuristics, the selection might fail to find composite Web services. To avoid such a failure, the tightness of a QoS requirement is defined and a workflow is determined to be partitioned according to the tightness. A mixed integer linear programming is utilized for the efficient service selection. Experimental results show that the success rate of partitioning is above 99%. Particularly, the proposed method performs faster and selects composite services whose qualities are not significantly different (less than 5%) from the optimal one.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.7
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• pp.1252-1273
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• 2011

In Web Service Composition (WSC) area, services selection aims at selecting an appropriate candidate from a set of functionally-equivalent services to execute the function of each task in an abstract WSC according to their different QoS values. In despite of many related works, few of previous studies consider transactional constraints in QoS-aware WSC, which guarantee reliable execution of Composite Web Service (CWS) that is composed by a number of unpredictable web services. In this paper, we propose a novel global selection-optimal approach in WSC by considering both transactional constraints and end-to-end QoS constraints. With this approach, we firstly identify building rules and the reduction method to build layer-based Directed Acyclic Graph (DAG) model which can model transactional relationships among candidate services. As such, the problem of solving global optimal QoS utility with transactional constraints in WSC can be regarded as a problem of solving single-source shortest path in DAG. After that, we present Graph-building algorithms and an optimal selection algorithm to explain the specific execution procedures. Finally, comprehensive experiments are conducted based on a real-world web service QoS dataset. The experimental results show that our approach has better performance over other competing selection approaches on success ratio and efficiency.

• Annual Conference of KIPS
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• 2012.04a
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• pp.586-589
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• 2012

Web Services have been utilized in a wide variety of applications and have turned into a key technology in developing business operations on the Web. Originally, Web Services can be exploited in an isolated form, however when no single Web Service can satisfy the functionality required by a user, there should be a possibility to compose existing services together in order to fulfill the user requirement. However, since the same service may be offered by different providers with different non-functional Quality of Service (QoS), the task of service selection for Web Service composition is becoming complicated. Also, as Web Services are inherently unreliable, how to deliver reliable Web Services composition over unreliable Web Services should be considered while composing Web Services. In this paper, we propose an approach on a QoS-aware Web Service selection for reliable Web Service composition. In our approach, we select and classify Web Services using Decision Tree based on QoS attributes provided by the client. Service classifier will improve selection of relevant Web Services early in the composition process and also provide flexibility to replace a failed Web Services with a redundant alternative Web Services, resulting in high availability and reliability of Web Service composition. We will provide an implementation of our proposed approach along with efficiency measurements through performance evaluation.