Consider the problem: Design a cordless powered screwdriver for use in home or small shop environments.
As a result of a situation brainstorming session, a team might end up with a list of statements about the product as shown below.
The SD provides plenty of power to drive screws
The SD makes it easy to start a screw
The SD works with a variety of screws
The SD can access most physical locations
The SD turns screws that are in poor condition
The SD feels good in the user's hand
The SD is easy to control while turning screws
The SD is easy to set up and use
The SD power is convenient
The SD lasts a long time
The SD is easy to store
The SD has a pleasant sound when in use
The SD looks like a professional quality tool
The SD is safe
Note that these statements are grouped into two or three levels. The main level identifies key issues, and the second level details out what the team (and presumably the client also) means by the main level issues, and the third level identifies key questions.
This three-level form often occurs naturally. A team member will identify some key factor, say convenience, and the facilitator3) of the brainstorming session will guide a short discussion (say, five minutes) on that one topic. Once the discussion dies down, the facilitator will move on to another topic, usually derived from the previous discussion.