As applications based on web increasing rapidly in terms of both scale and complexity, it has been well recognized that web has evolved from a hypermedia information medium into a new distributed application platform and it is proper and prospective to view web applications as software. Developing and maintaining large and complex web applications demands a systematic process and an effective engineering methodology. A suitable model of web application that can capture its features is crucial and fundamental to the establishment of such approaches. In this paper, based on our understanding of web applications as software, we propose a component oriented web application model, in which a web application is regarded as a collection of components, each having its own functionality and cooperating with others through certain interfaces. It is aimed at establishing a foundation for an engineering methodology of more effective web application development and maintenance that can benefit from the notion of component-oriented approach.