Chapter 2: Implementation Models and Mental Models

The computer industry makes frequent use of the term computer literacy. Pundits talk about how some people have it and some don't, how those who have it will succeed in the information economy, and those who lack it will inevitably fall between the socioeconomic cracks. Computer literacy, however, is nothing more than a euphemism for making the user stretch to understand an alien logic rather than having software-enabled products stretch to meet the user's way of thinking.

In this chapter, we discuss how a lack of understanding of users and the way they approach digital products has fueled the computer-literacy divide, and how software that better matches how people think and work can help solve the problem.

Implementation Models

Any machine has a mechanism for accomplishing its purpose. A motion picture projector, for example, uses a complicated sequence of intricately moving parts to create its illusion. It shines a very bright light through a translucent, miniature image for a fraction of a second. It then blocks out the light for a split second while it moves another miniature image into place. Then it unblocks the light again for another moment. It repeats this process with a new image twenty-four times per second. Software-enabled products don't have mechanisms in the sense of moving parts; these are replaced with algorithms and modules of code that communicate with each other. The representation of how a machine or a program actually works has been called the system model by Donald Norman (1989) and others; the authors prefer the term implementation model because it describes the details of the way a program is implemented in code.