Do you really need to do all of this?
You are probably thinking that this all sounds like an awful lot of work, and you probably want to get started on the actual use-case modeling without producing reams and reams of additional documentation.
Well, projects are typically in one of four states when the use-case modeling activities are scheduled to commence:
A formal Vision document has been produced.
The information has already been captured but not consolidated into a single Vision document.
There is a shared vision, but it has not been documented.
There is no vision.
If your project is in one of the first two states, and the information is available to all the stakeholder representatives, then you are in a position to proceed at full speed with the construction and completion of the use-case model. If your project is in one of the last two states, then you should be very careful not to spend too much effort on the detailed use-case modeling activities. This does not mean that use-case modeling cannot be startedit simply means that any modeling you do must be undertaken in conjunction with other activities aimed at establishing a documented vision for the product. In fact, in many cases, undertaking some initial use-case modeling can act as a driver and facilitation device for the construction of the vision itself.
Our recommendation would be to always produce a Vision document for every project and to relate the information it contains to the use-case model to provide focus, context, and direction to the use-case modeling activities. For-mally relating the two sets of information also provides excellent validation of their contents and quality. If there is sufficient domain knowledge and agreement between the stakeholder representatives, then producing and reviewing the Vision document can be done very quickly. If there isn't, then there is no point in undertaking detailed use-case modeling; the resulting specifications would be ultimately worthless as they would not be a reflection of the product's true requirements.