observation | the development of large systems, with which potential users will be performing complex tasks, because observation, and analysing the resulting information, can consume a large amount of time | a lot of time | taking a notebook and 'shadowing' important potential users as they do their work, writing down everything they do, asking users to talk as they work and explain what they are doing, and perhaps videotaping the session so you can analyze it in more detail later | | to gather subtle information that stakeholders may not think of telling you | requirements gathering |