It is often very important to convey the idea of a project plan or proposed new service in a very realistic way if expensive pitfalls are to be avoided. In a number of cases, even the key players involved in a new project do not share the same view of the way the system will eventually look. Some get so involved with details they completely overlook what the whole project is intended to deliver. Unfortunately this statement can apply.
What is the difference between a project and a race?
In a race, when the starting pistol fires, everyone runs in the same direction.

A project or concept demonstrator can let everyone clearly see what it is they are involved with. The demonstrator should be more than one single thing. It should use a variety of appropriate approaches and provide a range of deliverables which together show everyone involved, clearly and unambiguously, what it is they are collectively striving to achieve.
The demonstrator may use a core artificial environment to show what the eventual system will look like and it may use this environment to stage typical scenarios from the future. This of course, will depend on what type of project or vision is being developed. Each case needs to be given the respect of a fresh approach designed just for that case. Other demonstrator deliverables should be created using this fresh approach.
The demonstrator should deliver something or rather, some things, which can be used to satisfy a range of needs. Such needs can include:
Scenarios are examples of typical events which are likely to occur when the vision has been realised. Although, a scenario could also be something that is not wanted and could serve as a warning about the new system. Scenarios are likely to be simplified examples which can make a range of points about how the new system will feel when operational. Scenarios are likely to involve typical players within the new environment.
A scenario can be useful to design because it forces detailed thought about for instance, what might be said when something happens or what might happen if something out of the ordinary occurs. Most scenarios will clearly explain the behaviour of the new system in a typical set of cases.
The design of project requirements is the domain of requirements engineers. However, requirements engineers must work from what they are told about the future system and from what detailed plans exist. The demonstrator and accompanying scenarios will show requirements in action and may also highlight missing or incorrect requirements. The demonstrator and scenarios are another way for a requirements engineer to construct requirements.
The demonstrator and scenarios could be used to identify a limited set of requirements for the future system or ultimate vision.