About face 3.0/3

"The way engineers must build software is often a given, dictated by various technical and business constraints. The model for how the software actually works is called the implementation model. The way users perceive the jobs they need to do and how the program helps them do it is their mental model of interaction with the software. It is based on their own ideas of how they do their jobs and how computers might work. The way designers choose to represent the working of the program to the user is called the represented model, which, unlike the other two models, is an aspect of software over which designers have great control. One of the most important goals of the designer should be to make the represented model match the mental model of users as closely as possible. It is therefore critical that designers understand in detail the way their target users think about the work they do with the software."

User interfaces should be based on user mental models rather than implementation models.



"Real-world mechanical systems have the strengths and weaknesses of their medium, such as pen and paper. Software has a completely different set of strengths and weaknesses, yet when mechanical representations are replicated without change, they combine the weaknesses of the old with the weaknesses of the new."

Don’t replicate Mechanical-Age artifacts in user interfaces without Information-Age enhancements.


"Most occupants of the beginner end of the curve will either migrate into the center bulge of intermediates, or they will drop off of the graph altogether and find some product or activity in which they can migrate into intermediacy. Most users thus remain in a perpetual state of adequacy striving for fluency, with their skills ebbing and flowing like the tides depending on how frequently they use the product. Larry Constantine first identified the importance of designing for intermediates, and in his book Software for Use, he refers to such users as improving intermediates. We prefer the term perpetual intermediates, because although beginners quickly improve to become intermediates, they seldom go on to become experts."

The users of a digital product mostly are neither beginners nor experts,the intermediates are the majority of the user group,so design for the intermediates is a quite important principle of the interactive design.


For Beginners
"A separate guide facility— displayed within a dialog box — is a fine means for communicating overview, scope, and purpose. As the user begins to use the product, a dialog box can appear that states the basic goals and tools of the product, naming the main features. As long as the guide stays focused on beginner issues, like scope and goals, and avoids perpetual intermediate and expert issues (discussed below), it should be adequate for assisting beginners."

For Experts
"Expert users constantly, aggressively seek to learn more and to see more connections between their actions and the product’s behavior and representation. Experts appreciate new, powerful features. Their mastery of the product insulates them from becoming disturbed by the added complexity."

For Intermediates
"Perpetual intermediates need access to tools. They don’t need scope and purpose explained to them because they already know these things. ToolTips (see Chapter 23) are the perfect perpetual intermediate idiom. ToolTips say nothing about scope and purpose and meaning; they only state function in the briefest of idioms, consuming the least amount of video space in the process."

What are these three different groups separately need.