There is a need to adopt a situated design perspective in designing computer-based tools that support knowledge work to better understand what it means for users, developers, and stakeholders to approach and capture the tacit knowing within the work context. The design situation is characterized as explorative and iteratively interpreted, a pursuit of the vision of the future system guided by local circumstances. Formal engineering methods, reducing development work to engineering endeavors based on a rationalistic perspective, are not sufficient. The situated design perspective is presented as a conceptual model of the design practice, highlighting its constituent worlds, processes, and relations. The model depicts designing as an explorative and sense-making process, navigating between what is wanted or envisioned and what may be negotiated and discovered. It emphasizes the importance of the artifact being designed as a means to capture, communicate, and discover what is possible in the work context. The model makes clear that the design process is highly situated, that it cannot take place outside the work context because of interdependent relationships. It is designing within the living work context, not design for an objectified one.