The Internet and the World Wide Web are no doubt the great developments in the history of Information Technology. Traditional websites have progressively evolved from the browsable and static information repositories to web-based distributed systems integrating databases and complex business functionalities with multimedia technologies. The popularity of web-based systems has grown manifold. Legacy information and database systems are being migrated to the Internet and web environment. These web-based systems have a significant impact on business and industry as well as on the daily lives of the people in the modern society. Electronic business is rapidly growing and making every business a global business removing its boundaries.

However, the development approach used for web-based systems has been ad hoc and lacks a systematic engineering process. As the complexity and sophistication of the web-based systems grow, there is a legitimate and growing concern for a systematic approach to specify and develop these systems since abstraction and modeling can manage complexity in a better way. So, several approaches have been proposed to address this concern. Currently there is no standard notation accepted industry wide for specifying the web applications. Many tool vendors adopt the UML to the web context making extensions to it; even then this adoption is not trivial. This article is organized as follows. Section 2 discusses the nature of web applications that makes it different from the traditional software systems and shows how the existingmodeling approaches fit in the requirements. Section 3 briefly discusses the efforts put in to extend the UML to capture different aspects of the web applications. Then it concludes.

In the early days of WWW, websites were considered as hypermedia information repositories. With the popularity of the web, the requirements changed a lot. These websites have evolved to web applications having many business functions carried over them [1]. They are sophisticated and complex like any other traditional software systems in an organization. They are different from the traditional software systems in several ways like concurrency, availability, unpredictable load, evolutionary nature, security, information presentation, navigation and aesthetics [2]. To accommodate these aspects a modeling language for web applications should facilitate the requirements capture, documentation, specification, design, visualization, construction, maintenance and evolution efficiently. Since a web application is regarded as an extension of the early day websites, modeling of it should address two broad aspects.