Interviewing techniques are one of the simplest, yet most effective methods of requirements elicitation. Interviews can either be structured around a specific set of questions, or
open-ended with the intention of gathering as much useful information as possible. In most cases both techniques are used in a single interview. Structured interviews have the advantage that all interviewees are asked the same questions and that critical questions are not inadvertently forgotten. In an unstructured interview the interviewer may ask a few leading questions but then allow the interview to develop in a less rigid fashion. This approach may unearth entirely new areas of discussion that had previously been overlooked. As both methods have their own advantages, it is often beneficial to combine both techniques in a single interview. Interviews are often conducted in stages, so that responses from the first round can be used to generate a deeper set of more focused questions for the second round. It is often useful to target the second round of interviews to stakeholders with specific responsibilities or interests related to the more targeted questions.