Minimize conceptual load:

The best way to minimize conceptual load is to design a simple set of commands and operations that gives good coverage in the problem domain. Then, instead of adding a lot of bells and whistles to cover special cases, just stop. The challenge is to find simple sets of commands with good coverage and power. Most of the conceptual complexity of many systems is created by nonessential commands and operations that could be integrated into the rest or just eliminated. Consider allowing the bounds to be set by the choice of a (powerful) external myth. We suggest building systems that have direct commands with 80 percent of the basic actions, and leaving it at that. Of course, completeness requires that the remaining 20 percent of functions, if really required by the application, be achievable through simple combinations of the basic operations.

• nathan
• February 14, 2010
• Human Factor
• Page 49
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States in conceptual models:

There are two requirements with respect to states: that they be few in number, and highly visible to the user. States must be minimized because they are a source of complexity in the user interface, and thus in the conceptual model. The more states there are, the more situations the user has to recognize and learn to use. The user's conceptual model needs to contain information about what defines a state, what changes it, and what remains constant from one state to the next. States must be visible by inspection to keep the user informed about what's going on. The visible indication of state can be spatial as well as verbal. It is easy for people to recognize configurations on the screen or in lights without much conscious attention.

If users don't recognize it for what it represents, it might as well not ...

• nathan
• February 14, 2010
• Human Factor
• Page 46-47
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Couple notes from the chapter on conceptual models:

A system is the designer's way of communicating an idea to the user.

To allow the user to create the intended conceptual model, the designer must construct an effective external myth.

Consistency of myth, then, is the foundation of a clear conceptual model.

Users must be able to develop a set of expectations that are met by the system, even in new situations. In other words, the system must behave predictably.

People have a much harder time dealing with variable response times than with slower but predictable responses. Variability in response times results in many unfulfilled expectations, and thus frustration.

• nathan
• February 14, 2010
• Human Factor
• Page 42-45
• Reply