Introduction

Abstract

The Web is a distributed, dynamic, and large information repository. It has now evolved to encompass various information resources accessible worldwide. Organizations across all spectra have already moved their main operations to the Web, which has brought about a fast growth of various Web applications. This has dramatically increased the need to build a fundamental infrastruc- ture for efficient deployment and access of the exponentially growing plethora of Web applications. The development of enabling technologies for such an infrastructure is expected to change the business paradigm on the Web. Web services have become de facto the most significant technological by-product. Simply put, a Web service is a piece of software application whose interface and binding can be defined, described, and discovered as XML artifacts [4]. It supports direct interactions with other software agents using XML-based messages exchanged via Internet-based protocols. Examples of Web services include online reservation, ticket purchase, stock trading, and auction. Stan- dards are key enablers of Web services [83]. Major industry players took a lead to set up crucial standards. This has greatly facilitated the adoption and deployment of Web services [48]. Three key XML-based standards have been defined to support Web service deployment: SOAP [85], WSDL [87], and UDDI [58]. SOAP defines a communication protocol for Web services. WSDL enables service providers to describe their applications. UDDI offers a registry service that allows advertisement and discovery of Web services.