Comparison with the Nielsen-Molich Evaluation Method

After settling on the term “usability engineering” and writing down all but one of the design rules in the previous section, we discovered that there had been one previous attempt widely respected among specialists in the field to capture what is known about software interface design in a collection of rules. This was a set of heuristics proposed in a 1990 paper [Nielsen&Molich] and further developed in Jakob Nielsen's 1994 book Usability Engineering [Nielsen].

Upon inspection, we discovered that our approach converges with Nielsen's to a remarkable degree. The few marked differences are as instructive as the similarities. We'll therefore walk through Nielsen's heuristics here, and later in this book we'll propose an adaptation of the Nielsen-Molich heuristic evaluation method that should be readily applicable even given the decentralized organization characteristic of many of today's Unix projects.

Visibility of system status

The system should always keep users informed about what is going on, through appropriate feedback within reasonable time.

Comment: Corresponds to our Rule of Transparency.

Match between system and the real world

The system should speak the users' language, with words, phrases and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order.

Comment:Corresponds to our Rule of Least Surprise.

User control and freedom

Users often choose system functions by mistake and will need a clearly marked "emergency exit" to leave the unwanted state without having to go through an extended dialogue. Support undo and redo.

Comment: Corresponds to our Rule of Reversibility

Consistency and standards

Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions.

Comment: Corresponds to our Rule of Modelessness.

Error prevention

Even better than good error messages is a careful design which prevents a problem from occurring in the first place.

Comment: We have no rule that directly corresponds.

Recognition rather than recall

Make objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate.

Comment: Corresponds to our Rule of Transparency.

Flexibility and efficiency of use

Accelerators — unseen by the novice user — may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.

Comment: We have no rule that directly corresponds.

Aesthetic and minimalist design

Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.

Comment: Corresponds to our Rule of Silence.

Help users recognize, diagnose, and recover from errors

Error messages should be expressed in plain language (no codes), precisely indicate the problem, and constructively suggest a solution.

Comment: Corresponds to our Rule of Failure

Help and documentation

Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user's task, list concrete steps to be carried out, and not be too large.

Comment: Corresponds to our Rule of Documentation and Rule of Failure, adding mores specific advice about documentation style.

Missing from Nielsen's heuristics are the Rule of Bliss, the Rule of Distraction, the Rule of Flow, the Rule of Seven, the Rule of Confirmation, the Rule of Automation, the Rule of Defaults, the Rule of Respect, and the Rule of Reality; however, the Rule of Reality is strongly implicit in the rest of the Nielsen-Molich method. We have no rule that directly corresponds to Nielsen's heuristics “Error prevention” and “Flexibility and efficiency of use

Part of the reason we set more rules is that we have a decade more of experience, during which some fundamentals of the problem have become clearer. Another reason, though, is that Nielsen's approach is like that of most other interface design gurus (such as Bruce Tognazzini, today's principal exponent of the Macintosh style) in that it works from the outside inwards, where ours works from the inside outwards. We are more influenced both by the Unix tradition of system design from the internals outwards, and by attacks on the UI design problem like [Raskin] that seek to generate design rules not just by empirical observation but from considerations of the deep structure of human cognition.

As we learn more, the similarities between outside-in prescriptions like Jakob Nielsen's and Bruce Tognazzini's (on the one hand) and inside-out prescriptions like ours and Jef Raskin's (on the other) increase. The most basic thing both approaches have in common is the understanding that, ultimately, excellence in user-interface design comes from identifying with the user's experience.