Working in a software project is a challenge. People with different backgrounds are together working towards the goal of delivering a run able piece of software. As the development proceeds, different guidelines such as: Technology, quality directives, user goals, customer goals, style guides etc. will influence the design. This report will focus on the design of the graphical user interface and discuss how it benefits from making the guidelines explicit in the design process. Today it is identified that interaction design has a problem of reaching practical use in software industry. This thesis will present an approach to interaction design that can be used in practice in the complex nature of software development. The approach stresses the importance of not having only one perspective on design. A design group needs to have more than the end user’s perspective when developing an interactive product. In order to fit reality and fulfill user goals in the design, it is important to make the design process and its guidelines explicit to the developers. During this spring I have been involved in a large software engineering project, developing the interface design of an instant messaging application. In this Master thesis, I will explain how I developed my approach to interaction design in the organization of a project. I will also describe my experiences of working with the method of persona in order to make the user goals explicit in the design. The main purpose of this report is to show a practical way of working with interface design. The work resulted in traceability of design decisions, which was not the goal of this project, merely the result of an approach to design.