Glossary » Design Principles

design for manufacture

a term from industrial design that emphasizes the importance of making tradeoffs so that designs are actually practical to manufacture at reasonable costs, in a reasonable amount of time, given the resources, personnel, and tools available. User interface designers need…

device independence

the ability for software to work with a variety of different input or output devices without having to worry about which ones exactly the user is using. This enables users, such as the disabled, to use whatever devices are most…

direct manipulation

performing operations by making changes to data directly, such as clicking on it, dragging it, resizing it, and typing over it, as opposed to indirect operations, such as typing in commands on a command line or using menus and dialog…

display inertia

the principle that when the display must be changed (during user input or a change in system state), the change is kept to the minimum necessary to reflect the changing information. Rather than updating the entire display, keep changes localized…

distraction

anything that draws a users attention away from their current focus or desired focus, usually sounds or moving visual displays (such as blinking text, automatically scrolling text, animations, and flashing menubars).

On rare occasions, distractions can actually be useful for…

distributed cognition

the notion of people thinking and solving problems collectively, rather than simply as isolated individuals. Those interested in distributed cognition are interested in how people communicate and jointly use artifacts to accomplish joint work.

diversion

any technique used to distract the user from the fact that the computer is busy processing so that the user doesn’t get bored, impatient, or frustrated. Techniques include presenting text to read, a picture, an animation, or a satisfying alternate…

diversity

things vary more than you’d ever expect. Users vary by preferences, skills, impairments, interests, language, and culture. Computers vary by operating system, processor speed, screen size, memory, and networking abilities.

Design for diversity, or expect to succeed with only a…

drag and drop

a direct manipulation capability that allows you to select and drag and object and drop it into another location, specifically referring to dragging from one application to another. This is a more direct approach than the traditional cut and paste…

dwell

the property of a control that keeps it from activating until it has been ‘held’ (or manipulated) for a certain period of time, thus preventing accidental activation from being briefly hit unintentionally.

dwell time

the time a user lingers at a certain step of a task, such as the time that a user holds the pointer over a button, or the time spent viewing an individual web page.

DWIM

do what I mean; an interface that allows flexible styles of user input and lets the user ask the computer to interpret “what-I-mean” (not what I say), generally involving a simple heuristic for guessing what the user is most likely…

ease of use

effectiveness at achieving a person’s goals in a way that is satisfying to that person, and is fast and error-free.

economy of effort

a principle of design process that says that design and production time should be in proportion to the value it produces in the quality of the final product serving users’ needs.

Also, a principle of interaction design that says that…

economy of expression

a design principle advocating that characteristics of a visual display should be maximally efficient in representing information — that things that are different should be represented differently and that each distinction should be a meaningful one.

effectiveness

the degree to which an interface facilitates a user in accomplishing the task for which it was intended. This normally refers to the degree to which errors are avoided and tasks are successful, measure by “success rate” or “task completion…

efficiency

the rate or speed at which an interface enables a user to accurately and successfully complete a task. While faster response time is usually better, consistent response time is also important.

ephemeral awareness

information about others and their activities that changes quickly, such as their current facial expression, location, or posture; as opposed to more permanent awareness information about them, such as their current address, job position, or favorite food.

error

(human error) the result of any action whose consequences are not what was intended by the person performing the action. Errors are commonly classified as slips (automatic processes interfering with an action) or mistakes (failures in reasoning or selection of…

escape key

a key on the keyboard used to exit a mode. This can apply to moving upwards through a hierarchy of screens or stopping the execution of a program. Also used to break out of a command mode (where typing issues…

event handler

a central software routine for applications in graphical user interfaces that processes events as they arrive, primarily user input such as keystrokes and mouse clicks, but also system events such as time-based triggers. The events arrive in an event buffer.…

explicit destruction

a design principle that suggests that anytime information is permanently deleted (or for that matter, any irreversible action is performed), the user should be required to explicitly indicate that the deletion/destruction is actually desired. This is important when deleting files,…

eye contact

in conversations, people are aware of when people are looking into their eyes or not, and they use eye contact to signal turn-taking and attentiveness. In conventional videoconferencing systems, the camera is spatially offset from the monitor for viewing other…

fail-safe

a property of a device or system that inherently prevents certain failure modes or errors. An example is the inability to start your car when it isn’t in ‘park’.

familiarity

the degree to which a user recognizes user interface components and views their interaction as natural; the similarity of the interface to concrete objects the user has interacted with in the past. User interfaces can be familiar by mimicking the…