International Journal of Computer Applications (0975 – 8887) Volume 14– No.1, January 2011 28 Comparative Study of Mechanisms for Web Service Discovery based on Centralized Approach Focusing on UDDI Netra Patil Associate Professor Sinhgad Institute of Business Administration and Research, Pune ABSTRACT A Web service is a set of related application methods that can be accessed programmatically over the Internet. Businesses can dynamically mix and match Web services to perform complex functionality with minimal programming. Web services allow buyers and sellers all over the world to find each other, connect dynamically, and execute transactions in real time with minimal human interaction. Web services are self-contained, self-describing modular applications that can be published, located, and invoked across the Web. While creating web applications using web service technology there is a need for selecting new web services which best suit our need at the moment. For doing this we require to specify our criteria for selection of web service. Apart from this, appropriateness and optimality are the challenging issues at the time of web service consumption. Web services are important for interoperability of applications and integration of large scale distributed systems irrespective of platform. Web service discovery mechanisms are equally important, especially as the latter has turn to be difficult task. This paper reviews the latest mechanism, techniques, architectures and models that have evolved in the web service discovery area. Keywords UDDI, P2P, METEOR-S, QoS, WSMX 1. INTRODUCTION There is increasing demand for dynamically integrating different business applications and services. Several architectures, techniques and mechanisms have been suggested for more flexible and scalable process environments. The growth of web services and service oriented architecture offer an attractive basis for realizing such architectures and mechanisms. Web Services have marked current web engineering methodologies and are universally supported by IT vendors and users. In short they are interoperable software components that can be used in application integration and component based application development. As the demand for web service consumption is increasing, a series of questions concerning the methods and procedures to discover the most suitable web service arises. In fact there is much hiding behind the discovery of a web service. This work aims to examine and analyze the different proposals in the area. Discovery of Web services is of great interest and is a fundamental area of research in distributed computing. Many researchers have focused on discovering web services through a centralized UDDI registry [18, 19, 26]. Although centralized registries can provide effective methods for the discovery of Web services, they suffer from problems associated with having centralized systems such as a single point of failure, and bottlenecks. In addition, other issues relating to the scalability of data replication, providing notifications to all subscribers when performing any system upgrades, and handling versioning of services from the same provider have driven researchers to find other alternatives. As Web services have begun to expand across the internet, users need to be able to efficiently access and share Web services. Production and interoperability of larger number of web services have lead to the emergence of new standards on how services can be published, discovered or used. Hence, mechanisms are required for efficient selection of appropriate web service instance in terms of quality and performance factors at the moment of the Web Service consumption. The discovery mechanism should offer a number of capabilities, recognizable at both development and execution time. During development, one may search a web service repository for information about available services. At execution, client applications may use this repository to discover all instances of a web service that match a given interface. Web service discovery mechanism in general is the task of locating a machine-processable description of a web service that may have been previously unknown and that meets certain functional criteria. 2. APPROACHES FOR WEB SERVICE DISCOVERY Traditionally, the Web service discovery processes involved manual interference. A set of Web service descriptions is discovered according to user requirements. These service descriptions are manually scanned and those services which satisfy user requirements are selected and composed. In distributed system integration environment, such manual intervention is impractical, cumbersome and time consuming. The approaches to Web services discovery can be classified as centralized and decentralized. UDDI falls under fully centralized approach that supports replication where central registries are used to store Web service descriptions. Having realized that replicating the UDDI data is not a scalable approach several decentralized approaches have been proposed. Two major operators, namely IBM and Microsoft provide public UDDI service. Web service discovery mechanisms include a series of registries, indexes, catalogues, agent based and Peer to Peer- Dr. Arpita Gopal Director MCA Sinhgad Institute of Business Administration and Research, Pune