||It has been proposed to make architectural design decisions first-class entities in software architecture representation. The actual means of capturing, representing and managing architectural design decisions is still an open issue of research. We present an approach for capturing requirements and design decisions during design and development. We integrate design decisions, requirements, scenarios, and their relationships along with other architectural elements directly in a single, consistent, and formally defined architecture model. Capturing, visualizing, and tracing of architectural knowledge are supported by an integrated set of tools working on this model. The approach supports comprehensive tracing between requirements, design decisions, other architectural elements, and implementation artifacts, impact analysis, and architecture analysis and evaluation.