- Web-based information systems (WBIS) include the website part and the system part, and easy-to-use website is particular critical to the success of WBIS. This paper argues that the easy-to-use website can only be developed based on the need of use in the user perspective and such need must be captured and modelled as communicational requirements in WBIS analysis. However current analysis and modelling techniques do not enable modelling of communicational requirements in WBIS development. This chapter addresses this problem and proposes a new modelling technique (dialogue act modelling technique) for modelling of communicational requirements by user-website interactive communication analysis. It shows that the user-website interactive communication model built for the website part of WBIS by the analysis is also useful in modelling of the system part of WBIS with object orientation. It concludes that user-website interactive communication analysis is significant in developing WBIS tow...