Abstract
Task-complete activity-oriented user interfaces require the processing of knowledge that is based on front-line tasks and user characteristics. This type of knowledge enables the support of end users along the flow of work they are part of. Task completeness requires a development process that allows developers to trace the analysis, design, and implementation for particular user interface solutions, starting out with a transparent model of work in a consistent and understandable way. The Task Analysis/Design/End User Systems (TADEUS) project has led to a development technique and an environment that meets both objectives. The key concepts of TADEUS are (a) the unifying, but semantically rich notation for the representation of the results from task analysis and design; and (b) the executable specification of user interfaces. A workflow-based interpreter implements the latter concept, enabling early feedback on task-based artifacts by end users. This way, the stringent TADEUS methodology together with the tool support lead to a significant increase of quality in use and a reduction of overall development effort to achieve user acceptance through task-complete design and implementation.