Glossary » l

landmark

a screen that is sufficiently distinct from others that users can easily remember it and, upon recognizing it, use it to establish their context and location.

language disorder

any of a variety of common cognitive impairments (that limit the production and understanding of language), such as dyslexia, and speech impairments. Many of these impairments can be assisted by reducing the linguistic complexity of the interface (which also helps…

lasso-tap

circling and tapping on an object with a pen — used as a selection technique in pen-based systems.

latching

the capability of a control to be set in a specific position (or state) and to remain in that position; the opposite of a spring-loaded mode.

latecomer

in groupware systems, a person who joins a session after the session was first started. In some groupware architectures, supporting new people joining a session after the initial session setup may be difficult.

latency

same as delay — a measure of the time it takes for a message to be transmitted across a network. The variance of the latency is also an important measure.

layout manager

a program that automatically determines the layout of graphics and user interface elements based on relationships and restrictions specified by the designer/programmer. A layout manager is particularly useful for handling layouts when a programmer cannot be certain of what graphic…

learn mode

a state in which the computer is “learning” by observing the user’s behavior. The term is often used to refer to the period when a macro is being defined by having each action the user performs added to the macro,…

learnability

a measure of the degree to which a user interface can be learned quickly and effectively. Learning time is the typical measure. User interfaces are typically easier to learn when they are designed to be easy to use based on…

learned helplessness

when a person has repeated experiences of failure at a task or skill and learns to assume that they aren’t capable, when in fact they may simply need to be taught from a different point of view or to break…

learner-centered design

designing around the specific needs of a learner; designing to foster learning. Similar to user-centered design (UCD), learner-centered design focuses on the tasks and goals of someone who is learning, motivates them, and helps them grow as they use the…

learning curve

used informally, the “learning curve” is simply the amount of time and effort people will need to master a new skill (such as a new piece of software). A “steep learning curve” is a more time-consuming learning period that may…

learning time

the amount of time it takes to acquire a new skill or piece of knowledge up to a given level of mastery. Since nothing is ever learned perfectly, target levels of mastery must be defined, such as the ability to…

legacy system

an old hardware or software system which is generally out-dated in some way, either based on obsolete hardware or using an older user interface (such as a character-based interface). The term is usually used when planning a new system to…

legibility

the clarity of visually-presented text, affected for instance by the size of the text, the contrast between similar letters, the quality of printing or display (whether the text is damaged or blurred), the line-spacing and word-spacing, and the shape and…

lens

a movable region on the screen (such as a large magnifying glass) that transforms information below it. Typical transformations might include magnification, fisheye views, information filters (by showing street names on a map, for instance), and graphics filters (blurring, tinting,…

lexicon

the set of terminology used in an application, including the set of commands and terms used for the objects in the application. A lexicon should be chosen that is as consistent as possible and that uses the natural terminology of…

light pen

an input device for selecting regions on a screen or drawing. Light pens are generally held up to the monitor and determine their position by detecting the timing of the monitor refresh at their location. Because of the need for…

Likert scale

a type of survey question where respondents are asked to rate the level at which they agree or disagree with a given statement. For example:

I find this software easy to use.
strongly disagree 1 2 3 4 5 6

…

line-oriented interface

A user interface based on a user editing individual lines of text at a time, especially with regard to early text editors. In such systems, instead of moving around in the document as in screen-oriented editors or graphical user interfaces,…

link

or hyperlink; a button within a document (hilited text or images) that allows people to move to another document, and thus to navigate through a set of documents, such as clicking through various sites on the web.

link rot

because websites are frequently appearing and disappearing (and moving to new addresses), some fraction of links to outside websites will become invalid links over time. The slow degeneration of a web page with many links, due to the occasional link…

little arrows

small up and down arrows that are used to increment and decrement a value, such as for adjusting a date or as part of a spin box, which is a text entry field for entering numbers.

live dragging

visibly moving an object as it is being dragged; for instance, moving a slider knob as someone drags it, instead of simply moving the outline of the knob (which is called a ghost indicator).

load testing

testing a software system to verify that it can handle high-volume use; for instance, checking that a website can handle a large number of simultaneous users, checking that a game can handle a large number of players, or confirming that…

locator

a general way of referring to any input device or input method for specifying a location (an x,y position) on a screen. Typically includes devices associated with moving a screen pointer, such as a light pen, mouse, trackball, pen or…

locked-in syndrome

a level of paralysis where people can make no voluntary movements other than direction of eye gaze, despite their consciousness and awareness. Communication channels are thus extremely limited, and a brain-computer interface is one possible computer interface that can work.…

lockin

a process that keeps running unless a person takes overt action to remove a constraint to before telling it to stop.

locking

in groupware and database systems, restricting access to an object that someone else is editing to prevent conflicts, such as inconsistent changes.

lockout

an error-prevention technique that keeps somebody from doing something until they’ve made an overt action to remove a constraint to doing it, such as cases where a login is required for dangerous actions (which might also be for security reasons).…

locus of attention

or focus of attention; the single source or location of sensory input that a person attends to at a given time, such as the point in space that they’re looking at and able to devote mental resources to interpreting. In…

logical input device

a hardware-independent way of expressing the functionality of an input device. Also useful as an abstract way of discussing the functionality of widgets on the screen. Though other logical devices are popular (such as a 3D input device), the 5…

logical punctuation

a recommended approach to placing punctuation where the punctuation is logically grouped with the part of the sentence it applies to, rather than where arbitrary rules imply it should go. For instance, your grammar teachers said to put commas and…

look and feel

The appearance (look) and interactive style (feel) of software whose uniqueness to a particular platform or application defines the aesthetics and values of that application and how users subjectively respond to it. The look-and-feel is considered the front end of…

loss-of-activation error

forgetting; an error that occurs when, after beginning a goal-directed behavior, the reason for starting it is forgotten.

Lotus Notes

Lotus Notes is a groupware system that provides users with email, workflow, calendars, task lists, and document-sharing. Its infrastructure allows convenient flexibility in delivering these features. Lotus Notes is primarily restricted to asynchronous groupware features, and not real-time communication capabilities.…

low vision

limitations of eyesight short of complete blindness. Low vision may include myopia, blurred vision, limited visual angle, spotted vision, darkened eyesight, fractured images, and blindspots. Approaches to helping this situation include using large fonts and imagery, using screen magnification tools,…

low-fidelity prototype

a prototype that is sketchy and incomplete, that has some characteristics of the target product but is otherwise simple, usually in order to quickly produce the prototype and test broad concepts.

luddite

a person who is anti-technology, even violently so; a person who is a critic of the overuse, misuse, or abuse of technology. The term is derived from the name of Ned Ludd, an 18th century riot leader who led workers…

luminance ratio

for displays, the ratio of the brightness of ambient light to screen brightness, which affects the legibility of the display.

lurking

participating in an electronic conference (chat, mailing list, bulletin board, etc.) as only an observer and not a contributor to the discussion/interaction. Lurkers are quite common and probably a valuable use of conferencing except where the level of participation is…