Computer-Aided Software Engineering (CASE) and in particular IDEs (Integrated Development Environments) tools play a major role in the software development and maintenance process. They promise to assist software engineers in achieving several complex software development tasks while increasing their productivity and performance. However, the complexity of their interfaces has made these tools not always useful and very difficult to learn and master. One of the causes for this complexity is the fact that these tools are functionality-oriented rather than human-centric. The interface of these tools has not been developed according to the real users' characteristics, and there is a gap between the user's conceptual model and CASE tool features. In this thesis, we proposed a framework to simplify the complexity of the interface. Our approach starts from the development of an effective set of developers' personae that model developers' behaviors and characteristics. Using these personae, we developed a method to reduce the complexity of CASE tools. This method combines a task-sensitive user interface metaphor with visual communication design principles. Several empirical studies were conducted while building and validating our framework. (Rozita Naghshin)