If you’ve read “About Face” (Cooper, Reimann, Cronin) you’ll recognise this diagram. It’s a great description of how a product can be closely related to the way it was built (the implementation model), or the way a user relates to it (the mental model).

Here are some products that are close to the implementation model:

• The command line
• IRC
• Opening files with VLC

Here are some ideas that pull implementation closer to a mental model:

• An email inbox
• A desktop in your operating system
• Folder icons in Explorer / Finder / GNOME

It never occurred to me that the same could happen in real life, but here it is, from a gym in Birmingham, UK. This is a sheet that members use to refer their friends (presumably in return for a discount).