- To define how the interface will work.
- is a concept from the real world that is used as a model for the computer system.
- helps the user to understand the system and enables the user to predict what features the interface might provide, even without actually using the system.
- For example, uses a checkbook metaphor for its interface, even to the point of having the users type information into an on-screen form that looks like a real check register.
- In other cases, the metaphor is implicit, or unstated, but it is there nonetheless. Many Windows systems use the paper form or table as a metaphor.