User analysis and user modeling provide important information for the development of usable interactive computersystems. The Usability Engineering Repository (UsER), a web-based collaboration platform, supports analysis,design, and evaluation in the corresponding processes. In order to take specific users into account, UsER integratesmodules covering various methods for user modeling within a development process. Users can be modeled onseveral levels of abstraction as personas, stereotypes or user classes. How they fulfill their tasks within their workenvironment may be outlined in organizational charts, task models, or scenarios. Mapped onto a lineardocumentation structure, model entities and descriptions can be interlinked to point out semantic relationships, easenavigation and allow tracing of user goals and requirements throughout the user-centered development process.