Nowadays, UML is the most successful model-based approach to supporting software development. However, during the evolution of UML little attention has been paid to supporting user interface design and development. In the meantime, the user interface has become a crucial part of most software projects, and the use of models to capture requirements and express solutions for its design, a true necessity. Within the community of researchers investigating model-based approaches for interactive applications, particular attention has been paid to task models. ConcurTaskTrees is one of the most widely used notations for task modelling. This paper discusses a solution for obtaining a UML for interactive systems based on the integration of the two approaches and why this is a desirable goal.