"Any event which has not been provided with some symbol will remain fortuitous and unrepeatable."
Designers of gestural interfaces face the same problem illustrators and artists have faced for several millennia: how do you display three-dimensional movement in a two-dimensional format? Luckily for us, our tool set is broader than just paper, although paper is still our major format for documentation and will likely continue to be for some time to come.
This chapter covers documentation for those on the development team (sometimes called specifications or requirements), not for end-users, although some of the documentation can certainly be repurposed for users. Chapter 7 covers communicating to users.
A current school of thought advocates skipping documentation entirely and heading straight into prototyping. If that's your philosophy and process (and you have the team or skills to do that), simply jump ahead to Chapter 6.
The difference between documentation and prototyping can be blurry. Often, one goes back and forth between them. One could also prototype first and document second if the purpose of documentation is to spell out the final design. For the purposes of this book, a prototype is an object that a user can interact with in some manner, not just view.
There are, however, good reasons for doing documentation. As Dan Brown explains in his book, ...