International Journal of Web Services Practices, Vol. 3, No.3-4 (2008), pp. 129-135 ISSN 1738-6535 © Web Services Research Foundation, Seoul, Korea 129 Abstract— Rapid growth of published Web services makes their discovery more and more difficult. Many approaches are proposed to solve this discovery issue. Most of them are interested only in Web service’s description itself and neglect the user-centric aspect of the discovery process. User’s involvement may be seen as contributing information, after using or testing a service, which marks the personal opinion on service’s functionality, quality or invocation cost. This kind of contribution is perceived as a participative aspect inside the Web 2.0 environment and can enhance the Web service discovery process. We illustrate in this research work, a collaborative tagging-based environment for Web service discovery, allowing users to tag or annotate a Web service using keyword or free-text. Our system proposes consequently two types of query to search tagged Web services: keyword-based and free-text. We put in place an advanced mode in the discovery by keyword which offers different ways to combine keywords together inside a query to make it more flexible and accurate. In both types of look-up (by keyword and by free-text), synonym relation between terms is processed in order to improve the similarity computing between a query and the tagged web services. The Web services found after a discovery process are ranked according to their tags’ weight, in the case of discovery by keywords. Index Terms— Web Service Discovery, Collaborative Tagging System, Vector Space Model, WordNet I. INTRODUCTION ROWNING into a great number of publicly accessible Web services, a user (a neophyte Web user who needs to start with Service Oriented Computing, a designer or developer of Service Oriented Applications) can be confronted with a difficult exercise when trying to find a Web service relevant to a requirement. Generally, these users have difficulties in Manuscript received 5 th December 2008. Uddam CHUKMOL is a doctoral student of INSA Lyon and he is conducting his research activity within the SOC (Service Oriented Computing) team of LIRIS laboratory – Université de Lyon, INSA-Lyon, LIRIS, UMR5205, F-69621, FRANCE (e-mail: uddam.chukmol@insa-lyon.fr). Aïcha – Nabila BENHARKAT is an Associate Professor in the Information Technology and Computer Engineering Department of INSA Lyon and she is also a researcher in the SOC (Service Oriented Computing) team of LIRIS laboratory – Université de Lyon, CNRS, INSA-Lyon, LIRIS, UMR5205, F-69621, FRANCE (e-mail: nabila.benharkat@insa-lyon.fr). Youssef AMGHAR is a Professor in the Information Technology and Computer Engineering Department of INSA Lyon and he is also a researcher in the SOC (Service Oriented Computing) team of LIRIS laboratory – Université de Lyon, CNRS, INSA-Lyon, LIRIS, UMR5205, F-69621, FRANCE (e-mail: youssef.amghar@insa-lyon.fr). exploring Web services in a few steps and, to the best that we know, nothing is available yet to facilitate the construction of their requests in a free-style, flexible, intuitive but efficient way. Most of the time, users discover Web services through a search interface using text based query with some advanced features or they have to construct their queries in a complicated formalism to express their searches’ requirement. We argue that both styles of query do not facilitate the Web service discovery. The reasons behind this affirmation are: firstly, simple keyword based discovery mechanism frequently offers low matching result in the current environments because they deal with poorly described Web services (insufficient textual description of Web services within WSDL files). Secondly, complicated formalisms used to construct discovery’s queries are often description logic based, which require efforts from not only the users while constructing their queries but also from the service’s providers to enrich their published services with description logic or ontological information. The search algorithms, in this case, have recourse to ontology usage and demand standardized ontology definition. Besides, we can consider the Web as the simplest environment for neophyte users to explore Web services as if they were executing an information lookup process. In effect, after the official shutdown of UDDI project in 2006, Internet has gained a real popularity as a global repository of Web services. We are able to find different Web sites providing access to Web services such as XMethods [23], WebServiceX.NET [25], StrikeIron [24], etc. Different existing works emphasize and confirm this statement. In [26], Internet is perceived as a natural source of Web services because Web service’s descriptions are hosted in various Web servers accessible by Web crawlers. A collection of Web services crawled from the Web is provided in [22]. In a simpler way, [28] uses different general purpose search engines in the service discovery process. These works allow us to argue that there are several interesting access points to active Web services that can be found on the Internet and using this world wide environment will bring Web services a large step closer to mass public users. Despite the fact that there are no sufficiently rich hyperlink structures between WSDL documents (Web service’s description), a Web based crawler can still be operational to collect this kind of files from the Internet [27]. Building a collection of Web services that are extracted from the Web can assure not only the public access to the services but also the regular update of services. We, henceforth, will focus our work Enhancing Web Service Discovery by using Collaborative Tagging System Uddam CHUKMOL, Aïcha-Nabila BENHARKAT and Youssef AMGHAR D