JOURNAL OF COMPUTING, VOLUME 1, ISSUE 1, DECEMBER 2009, ISSN: 2151-9617 119 HTTPS://SITES.GOOGLE.COM/SITE/JOURNALOFCOMPUTING/ Analysis on the Study of QoS-Aware Web Services Discovery T. Rajendran and Dr. P. Balasubramanie Abstract— Web service technology has gained more important role in developing distributed applications and systems on the Internet. Rapid growth of published Web services makes their discovery more and more difficult. There exist many web services which exhibit similar functional characteristics. It is imperative to provide service consumers with facilities for selecting required web services according to their non-functional characteristics or QoS. The QoS-based web service discovery mechanisms will play an essential role in SOA, as e-Business applications want to use services that most accurately meet their requirements. However, representing and storing the values of QoS attributes are problematic, as the current UDDI was not designed to accommodate these emerging requirements. To solve the problems of storing QoS in UDDI and aggregating QoS values using the tModel approach. The aim is to study these approaches and other existing QoS tModel representation for their efficiency and consistency in service discovery. This paper discusses a broad range of research issues such as web service discovery or web service selection based on QoS in the E-Business domain. Index Terms— Quality of Service (QoS), UDDI, Web Services, Web Services Discovery. —————————— —————————— 1 INTRODUCTION ERVICE-Oriented Architecture (SOA) supports soft- vision calls for a seamless integration of business proc- Sware to be composed from services dynamically. The esses, applications, and Web services over the Inter- SOA is “an architecture that represents software func- net.Web service technology enables e-business and e- tionality as discoverable services on the network” [4]. commerce to become a reality. It has become a competi- SOA provides methods for systems development and tive tool of companies by reducing cost through fast, ef- integration where systems group functionality around fective, and reliable services to customers, suppliers, and business processes and package these as interoperable partners over the Internet. It enables more efficient busi- services. An SOA infrastructure allows different applica- ness operations via the Web and enhances business op- tions to exchange data with one another as they partici- portunities to companies. With the widespread prolifera- pate in business processes. Web Services form the core of tion of Web services, quality of service (QoS) will become e-business and hence, have experienced a rapid develop- a significant factor in distinguishing the success of service ment in the past few years. Web Services, which are based providers. Due to the dynamic and unpredictable nature on XML-based open standards, promise the interoperabil- of the Web, providing the acceptable QoS is really a chal- ity of various applications running on heterogeneous lenging task. Applications with very different character- platforms. They enable dynamic connections and automa- istics and requirements compete for scarce network re- tion of business processes within and across enterprises sources. Changes in traffic patterns, denial-of-service at- for enterprise application integration and business-to- tacks and the effects of infrastructure failures, low per- business integration. Building on the ubiquitous and formance of Web protocols, and security issues over the lightweight standards that are supported by major soft- Web create a need for Internet QoS standards. Often, un- ware vendors, Web services enable application integra- resolved QoS issues cause critical transactional applica- tion via the publishing of application's functionality as tions to suffer from unacceptable levels of performance services, as well as location and invocation of services degradation. With the growing popularity and an exten- over the Internet. sive deployment of Web services, the consumers of Web Web Services are based on a collection of standards services will rather want a means to distinguish QoS- and protocols that allow us to make processing requests aware Web services from QoS-unaware Web services. to remote systems by speaking a common, non- According to the specification designed by the World proprietary language and using common transport proto- Wide Consortium (W3C), QoS requirements for Web ser- cols such as HTTP and SMTP. The dynamic e-business vices include the following ten major requirements: per- formance, reliability, scalability, robustness, accuracy, ———————————————— integrity, accessibility, availability, interoperability and • T.Rajendran is an Assistant Professor cum Research Scholar, Department security. Given that the QoS-aware Web services can of Computer Science & Engineering, SNS College of Technology, Coimba- carry a higher business value than other Web services, the tore, Tamilnadu and India. • Dr.P.Balasubramanie is a Professor, Department of Computer Science & Web service providers and requesters would benefit from Engineering, Kongu Engineering College, Perundurai, Tamilnadu and In- this kind of services. Web services are new forms of dia. © 2009 Journal of Computing http://sites.google.com/site/journalofcomputing/ JOURNAL OF COMPUTING, VOLUME 1, ISSUE 1, DECEMBER 2009, ISSN: 2151-9617 120 HTTPS://SITES.GOOGLE.COM/SITE/JOURNALOFCOMPUTING/ Internet software which can be invoked using standard formed after the above matching step. Because different Internet protocols. Web Services, as it is defined by the service providers and requesters may use different lan- World Wide Web Consortium (W3C), is a software sys- guages [5], [6], [7], [8] and models [9], [10], [11],[12], [13] tem designed to support interoperable machine-to- for QoS advertisements and requirements, it is necessary machine interaction over a network. Web services interact to find a way for a system understanding different QoS with each other, fulfilling tasks and requests that, in turn, concepts in QoS descriptions. Besides that, different do- carry out parts of complex transactions or workflows. mains and applications may require different QoS proper- UDDI is a platform-independent, XML-based registry ties; therefore we need a more efficient and flexible for businesses worldwide to list them on the Internet. method to express QoS information. A study of Web ser- UDDI is an open industry initiative, enabling businesses vice discovery system is needed to explore existing tech- to publish service listings and discover each other and niques and to highlight the advantages and disadvan- define how the services or software applications interact tages of each system. over the Internet. UDDI defines a registry for service pro- The rest of the article is as follows. The section 2 intro- viders to publish their services. UDDI is like a registry duces the background of Web service model, the Web rather than like a repository. A registry contains only ref- services description languages and the UDDI registry erence information. WSDL is used to describe a web ser- with QoS. Section 3 provides the QoS requirements for vice’s capabilities and the interface to invoke it. A WSDL web services. Section 4 describes the area of web services document is self-describing so that a service consumer discovery. The section 5 presents the issues related to can examine the functionality of the web service at run- Web services Discovery with QoS, followed by the con- time and generate corresponding code to automatically clusion in the section 6. invoke the service. The interface definition (WSDL) speci- fies the syntactic signature for a service but does not spec- 2 WEB SERVICE MODEL ify any semantics or non-functional aspects.All these standards are XML-based (eXtensible Markup Language), In a Web service model, a service provider offers Web which allows applications to interact with each other over services which provide functions or business operations networks, no matter what languages and platforms they which can be deployed over the Internet, in the hope that are using. The two features, self-description and lan- they will be invoked by partners or customers; a Web guage- / platform-independence, distinguish web ser- service requester describes requirements in order to locate vices from other distributed computing technologies, like service providers. Publishing, binding, and discovering CORBA and DCOM. Web services are three major tasks in the model. Discov- Fundamentally, standards like WSDL can support ser- ery is the process of finding Web services provider loca- vice providers describe their services’ functionality tions which satisfy specific requirements. Web services through standard interfaces and advertise them in some are useless if they cannot be discovered. So, discovery is UDDI registries. When a service request is issued, avail- the most important task in the Web service model. The able Web service descriptions and the service request de- Web service model in Fig. 1 shows the interaction be- scription is matched together in order to find the services tween a service requester, service providers, and a service that can provide expected functionality (the matching discovery system. step). However, Web service functional descriptions are 1. The service providers offer Web services which not sufficient for service discovery process. There are sev- provide functions or business operations. They eral reasons for this fact. Firstly, a key advantage