1.6 Create a Mock-Up or Prototype

After thinking through the paper description of the design, it's time to build something more concrete that can be shown to users and that can act as a more detailed description for further work. In the early stages of a simple design, this concrete product might be as simple as a series of paper sketches showing the interface while a user steps through one of the representative tasks. A surprising amount of information can be gleaned by showing the paper mock-up to a few users. The mock-up may even reveal hidden misunderstandings among members of the design team.

For further analysis, the design can be prototyped using a system such as HyperCard, Dan Bricklin's Demo Package, or any of an increasing number of similar prototyping tools. It may even be possible to build a prototype using the User Interface Management System (UIMS) that will be the foundation of the final product. This approach can be especially productive, not only because it reduces the amount of work needed to create the production system, but also because interface techniques tested in a stand-alone prototyping system may be difficult to duplicate in the production UIMS.

The entire design doesn't need to be implemented at this stage. Initial efforts should concentrate on parts of the interface needed for the representative tasks. Underlying system functionality, which may still be under development, can be emulated using "Wizard of Oz" techniques. That is, the designer or a colleague can perform the actions that the system can't, or the system can be preloaded with appropriate responses to actions that a user might take. (The design team needs to take care that users and management aren't misled into thinking the underlying system is finished.)