Glossary » Design Principles

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…

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…

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…

mental integration

when the user is required to remember an item from a previous page to compare it to something on the present page, just the opposite of physical integration. Better designs will make it easier for the user to compare items…

mental map

(website navigation) a representation in a person’s mind of the structure of a website, which is likely to be incomplete and simplified. A mental map helps people simplify the job of remembering what they’ve seen to the problem of remembering…

merchantability

the degree to which a product is fit for its intended purpose, the degree to which it works correctly and is suitable for someone to purchase and use without serious risk. The term is directly about whether it is appropriate…

metaphor

the use of one idea or object to represent another; making an implicit comparison between concepts to provide insight into those concepts.

Metaphor is used widely in graphical user interfaces to help set users’ expectations and make the behavior of…

Metcalfe’s Law

the impact of a network is proportional to the square of the number of nodes, which is roughly the number of possible connections (n(n-1)/2). Proposed by Bob Metcalfe, inventor of Ethernet.

Meyer’s Law

T = A + B * SQRT(D/W)

T = time to move to a target
D = distance to target
W = width of target
A ~ -13 msec
B ~ 108 msec

Meyer’s Law is…

minesweeping

the activity of moving the pointer across icons to uncover ToolTips or rollovers in order to figure out what the icons represent. Such designs require the user to actively decipher the interface, probing and testing the meaning of each interface…

minimalism

a principle of design that advocates eliminating all unnecessary decoration, distraction, and redundancy. In task design, eliminate unnecessary steps and alternatives in order to achieve efficiency, reduce decision time, and reduce errors caused by following incorrect paths. Write concise, factual…

mistake

an error of reasoning or inappropriate subgoals, such as making a bad choice or failing to think through the full implications of an action.

modal

a type of interface where the user moves between different states, or modes. In each mode, input from the user is interpreted in a different way. When a user is in a given mode, it’s a good idea to provide…

mode error

a type of slip where a user performs an action appropriate to one situation in another situation, common in software with multiple modes. Examples include drawing software, where a user tries to use one drawing tool as if it were…

modeless

a type of interface where the user is free to perform any action in the interface and the interpretation of user input is the same at all times. That is, mouse clicks always have the same effect and keystrokes always…

netiquette

polite ways of behaving on the internet, such as:

…

obviousness

a principle that user interfaces should be clear and straightforward. Nothing should confuse the user. An interface should be simple, avoid jargon, use natural language, and avoid hiding features. It should fit a user’s task — if you want to…

opaqueness

or opacity; the property of an interface whose method of use is not at all apparent in its design and must be learned.

opportunistic goals

user goals that are formulated on the spot in reaction to prominent system events or displays that suggest those goals.

out-of-box experience

OOBE; the interactions and first impressions a user has with technology when first opening the box it comes in and installing it, as opposed to the point-of-sale experience or the interaction experience of an expert user.

The out-of-box experience affects…

performance measure

a quantitative rating on how someone performed a task, such as the time it took to complete, the number of errors they made in doing it, their success rate, time spent in a particular phase of a process, frequency with…

personalization

modifying an application with personally-relevant information for an individual user, such as providing their name, email address, or favorite color.