Glossary » Design Principles

Fitts’ Law

T = k log2(D/S + 0.5), k ~ 100 msec.

T = time to move the hand to a target
D = distance between hand and target
S = size of target

Fitts’ Law is a model to…

floor control

the mechanism by which access to a shared object is mediated — for instance, controlling access to a shared whiteboard (so only one person can draw at a time) or determining who can speak during a chat session (determining who…

focus+context

a principle of information visualization — display the most important data at the focal point at full size and detail, and display the area around the focal point (the context) to help make sense of how the important information relates…

forcing function

an aspect of a design that prevents a user from taking an action without explicitly performing another action. For example, writing on a PDA won’t have any effect unless you first turn it on, preventing data corruption from accidentally bumping…

forgiveness

a design principle that says people should be able to recover from their inevitable mistakes. Dialog boxes should have a Cancel button. Operations should be undoable. Long operations should allow a user to stop them in the middle.

The most…

form follows function

a design aesthetic that encourages design to be grounded on the functional, useful forms inherent in the application. This avoids gratuitous decoration but elevates the human task and the meaning of the object as the principle aesthetic.

fundamental attribution error

the tendency for people to blame themselves rather than external factors for problems they have. In computer terms, the tendency to blame the user rather than the technology or its design when users have trouble with computers.

garden path

a sequence of actions a user takes that each seem to be leading to the desired outcome but don’t produce the desired result in the end, such as navigating thru a series of apparently-relevant website links without finding the desired…

gaze awareness

the ability to tell what someone is looking at by watching the direction of their eyes. In videoconferencing systems, gaze awareness may be an important aspect of effectively communicating. For videoconferencing, gaze awareness is a more relaxed design principle than…

gee whiz factor

that aspect of a design which shows off a technical skill or a sensational design that makes people say “that’s neat!”, but really has no useful purpose.

gestalt principles

principles of perception that address the interpretation of arrangements and relationships of objects; the whole is greater than the sum of the parts. Some of the common principles are:

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glance

a view that automatically closes after a brief delay, thus freeing the user from the overhead of determining when and how to close the view. Used in videoconferencing, a glance enables a person to quickly check on the availability of…

graceful degradation

the quality of a system or design such that when something goes wrong, it happens a little at a time and with plenty of opportunity to take action to correct the problem or at least protect against its worst consequences.…

graceful flow

a design principle which advocates that a user’s experience in interacting with a computer should involve a smooth and graceful dialog. In terms of the user’s task, this means that response time should be rapid and user errors and error…

guidelines checklist

a type of usability inspection; a list of rules for interface design to confirm are followed in a user interface being evaluated. These rules may include broad principles such as simplicity, may be empirically-derived results for improving speed and accuracy,…

habituation

developing a habit, a fixed pattern of responses to given situations, which becomes fast and automatic but can lead to user errors when those patterned responses don’t apply, as in modal systems.

hacker ethic

the value system espoused by an ill-defined collection of hackers, programmers and other technologists who love working with computers. The primary value is that all information should be free, and this has been reflected in shareware and open source code…

hedonic quality

(hedonism: the unrestrained pursuit of pleasure) the aspects of a user interface that appeal to a person’s desire of pleasure and avoidance of boredom and discomfort. The aspects that are fun, original, interesting, engaging, and cool. A positive subjective experience.…

hit logs

statistics on which pages are getting visited on a website, useful for determining which pages are popular, which may be difficult to find, and which paths people are taking through the website.

The logs may contain information on what date…

hot-swappable device

any hardware input or output device that can be plugged into a computer or removed from it while the computer is “hot”, turned on and currently running software, so that the device can be detected and used by software and…

hover state

the appearance or behavior of a button or other control while the pointer is over it but the item has not been clicked or dragged; most often used to hilite buttons as the pointer moves across them to indicate that…

human anthropometry

anthropometrics; the measurement of the physical characteristics of humans, particularly length and weight measures, used for industrial design, especially the design of furniture, vehicles, and workspaces. In the domain of computer use, such measurements apply primarily in the design of…

hysteresis

resistance to applied force, e.g. viscosity. Applied to keyboard keys and the feel of resistance they give, and appropriate to all interactions where the interface resists change, lags in response, or dampens the magnitude of the input (e.g. an icon…

idiom

a common practice or conventional approach to something, often based on a metaphorical comparison to real-world activities. A standard that is followed and provides familiarity and consistency for users.

idiot-proof

a less-than-friendly term for a user-friendly system, emphasizing its minimal learning curve for novices and robustness in preventing and handling user errors.