Glossary » Design Principles

scanning

for the physically disabled, the ability to move through a set of options (usually automatically) and to select one of the options. This enables an interface with only one input: “select now”. With this interface, a user can select objects…

screen pop

a feature in telephone-based customer service applications that brings up a customer record automatically on the screen of the customer service representative when they receive a call.

see-and-point interface

a user interface that displays objects and options, and a user only has to point to (and click on) the relevant object to issues commands and perform tasks. See-and-point interfaces are in contrast to remember-and-type interfaces that do not have…

semantic directness

the degree of translation required from a user’s conceived goal to the action needed to achieve the goal, based on how that action is supported by system features.

sense of presence

the degree to which people feel that they are co-located with the others they are interacting with despite the fact that they are communicating over a distance using technology. The sense of presence might be enhanced, for instance, by: more…

sensory modality

A communication channel associated with one of the human senses of sound, vision, touch, smell or taste. As used in discussing usability this may imply input to and output from the computer as well as the human user. E.g., the…

session control

the mechanism for mediating which people and which objects can belong to a given interactive session.

Important issues are the means by which users enter and leave a session, how a session is started and ended, and what resources are…

shortcuts

any means of providing a faster method to accomplish a task than the general-purpose method, such as assuming typical default values. Shortcuts can be provided for experts that novices might have difficulty using, such as inconsistent methods for common tasks,…

side effects

actions that occur as the result of a user action which do not seem to the user to be related to the primary goal of the action. For instance, when starting a game changes system configurations (such as screen and…

simplicity

the principle that user interfaces should be “simple” for users. Simplicity is used loosely to refer to the need to minimize the number of steps involved in a process, to use symbols and terminology that make the interface as obvious…

slip

(psychology) an error resulting from skilled behavior being performed at a time when it shouldn’t, such as accidentally driving to the office when you intended to drive to the store. Highly-practiced behaviors become automatic and the triggers for these automatic…

slow in and slow out

in animation, the acceleration and deceleration of action, i.e. the way that an action begins slowly, moves quickly through the main action, and then slows down as it comes to a stop rather than moving linearly from one position to…

snapping / gravity

a graphics input technique – when people draw or drag objects near a gridline, guideline, or another object, the object they are drawing or moving automatically jumps into alignment (snaps) as soon as it gets close, as if the guideline…

social responsibility

the notion that computing should be used to further the welfare of humankind, and that as designers, we ought to put strong focus on ethical issues such as safety, privacy, accessibility, respect for the users, human empowerment, achievement, and dignity.…

speech act

a view of language that treats communication as a series of actions in the form of speech, where each action is intended to cause some change in the world outside the speaker, whether it be:

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speed

a metric for human performance. How quickly does a person react to a stimulus (reaction time)? How much time does it take for someone to perform a given task (task completion time)?

Also, a metric for system performance. How quickly…

speed-accuracy tradeoff

in many types of perceptual-motor tasks, there is a tradeoff between how fast a task can be performed and how many mistakes are made in performing the task. That is, a user can either perform the task very fast with…

spring-loaded mode

also called a user-maintained mode or quasimode. A mode that must be actively maintained by the user, such as the use of the shift key on a keyboard, where other keys are only interpreted as capital letters while the shift…

squash and stretch

in animation, elastic distortions of shapes during motion, especially of living creatures, to reflect the stretch of elastic body tissue, such as cheeks stretching and bulging during chewing. These distortions may be exaggerated to clarify an action, but the common…

staging

in animation, the choice of composition, viewpoint, and acting to communicate most effectively without confusion, distracting details, or tradeoffs that sacrifice clarity.

standard

or “norm”; a rule for how user interfaces should be designed for given tasks, users, and contexts. User interface standards are usually encoded in style guides and are available for every major operating system. Standards help to ensure consistency across…

stereopsis

the perception of depth based on the differences in images that reach the 2 eyes.

stimulus-response compatibility

the degree to which what people perceive is consistent with the actions they need to take.

Saying “red” when you see a red light go on is an example of high compatibility. Having to say “green” when a red light…

subjective rating

any rating that a person gives that is based on their subjective reaction or opinion, their feelings, desires, priorities, etc. While the rating is subjective, it is often measured on a Likert scale, which allows for a quantitative measure that,…

synthetic metric

a value which is the result of combining other metrics, which are measurements of properties of designs, systems, or user performance. An example is to average the results of several subjective ratings scores that come from users responding to an…