Glossary » p

paddle

a small round input device that a user can spin clockwise or counterclockwise (either mounted, or usually held in the opposite hand). The direction and speed of movement, rather than the absolute position, are the relevant measured parameters. Paddles were…

page schematic

or static wireframe; a drawing showing the basic navigation and content elements of a web page, without detailed content or concrete visual layout. The idea is to reveal which navigation elements appear on a page, e.g. top-level, second-level, breadcrumbs. This…

page-oriented scrollbar

a scrollbar that indicates the page number of a document as the user moves the scroll thumb (scrollbox). The page number may be indicated inside or beside the scroll thumb or on a status line. The scrollbar may also have…

panning

an alternative to scrolling for moving the viewed area within a window – the user drags the view (and usually the pointer changes to a flat hand) in 2 dimensions (instead of the 1-dimensional scrollbar).

In video, panning refers to…

paper-and-pencil prototype

a paper sketch of a user interface with enough detail to make design decisions and usability evaluations, whether through a usability inspection, a focus group, or a simple user test.

parallel design

two or more separate design groups create design proposals independently and then come together to compare ideas before committing to a single design approach. This is similar to brainstorming techniques that encourage independent idea generation in order to come up…

parametric search

a search done that fits a number of simultaneous criteria (the parameters of the search). For example, finding a house within one of three neighborhoods, $3-600,000, with at least 3 bedrooms and 2 baths.

A typical difficulty for users with…

participant observation

observing people by joining them in their activity, e.g. working with people in their workplace to see how they use an office computer system, playing games at the arcade with other game players, or joining a programming team to understand…

participatory design

a democratic approach to design that encourages participation in the design process by a wide variety of stakeholders, such as: designers, developers, management, users, customers, salespeople, distributors, etc. The approach stresses making users not simply the subjects of user testing,…

password field

a text entry field for entering passwords. As a person types, a password field typically conceals the password by displaying blocking characters, “*”, instead of the actual letters typed.

path

a custom sequence of documents that are navigated through a hypertext or hypermedia system, intended to provide a “guided tour” or a “lesson plan” with interesting and useful stopping points.

pause removal

in auditory interfaces, speech and other recordings can be shortened by removing empty spaces where only background noise is heard. This speeds up playback when the audio is reviewed.

payoff matrix

in game theory, a matrix showing the consequences of interactions between 2 players. Each dimension shows the range of choices for each player, and each cell specifies what happens for that pair of choices.

payoff page

(web) the target page that a user arrives at after clicking on a banner ad or candy box. The payoff page should satisfy the user’s purpose in following the link while additionally informing the user, persuading the user of a…

PDA

personal digital assistant; a hand-held computer, typically with the capabilities of a personal information management system, such as a clock, appointment book, and address book.

pen-based computing

interacting with computers using a pen, as opposed to a keyboard or mouse. A pen allows fluid handwriting, gestures, and sketching that are difficult with many other input devices, thus enabling a more expressive form of input. Pen-based interfaces are…

percent-done indicator

a type of progress indicator where the percentage completed is also displayed.

perceptual user interface

PUI; a user interface that maximizes the bandwidth of communication between a user and a computer, using multimedia to capitalize on all the user’s senses, and using multiple input modalities. This enables a user experience that is more like the…

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…

persona

a description of a specific person who is a target user of a system being designed, providing demographic information, needs, preferences, biographical information, and a photo or illustration. Typically, multiple personas are developed in the early stages of design that…

personalization

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

perspective wall

a way of densely displaying large amounts of information by placing information on a flat plane which is tilted into the screen so that it shrinks back toward infinity. More important items (such as upcoming dates on a calendar) can…

persuasive computing

or “captology”; the use of computing technology to change or influence attitudes or behaviors. Examples include advertising, public service messages, and demo and attract-mode screens used for point-of-sale displays and arcade games.

Many important ethical issues need to be considered…

PERT chart

(Program Evaluation and Review Technique) a type of flowchart used in project management, where each task is represented by a node and connected to other tasks with arrows to indicate task dependencies. Each node may be labeled with necessary resources…

pervasive usability

a principle of design that advocates the application of usability methods in every stage of the design process. Some of the primary stages of design, and some example usability techniques, are:

requirements gathering: field studies, interviews, focus groups requirements

…

physical integration

when items that have to be compared are side by side on the screen so people can see both things simultaneously and not have to remember something from a previous page or have to scroll up or down to find…

pick device

a general way of referring to any input device or input method for selecting an object or selecting information. A wide range of devices can be used for this purpose, including a touch screen, mouse, thumbwheel, or cursor keys.

pie menu

a circular menu of options radiating out from where the user clicks. Each option occupies a pie slice. Because each option is equally distant, menu selection can be faster than with traditional pull-down menus. The geometry of the pie menu…

pilot test

or formative test; an initial run of a study (e.g. an experiment, survey, or interview) for the purpose of verifying that the test itself is well-formulated. For instance, a colleague or friend can be asked to participate in a user…

PIM

personal information manager; a software application designed to help people manage personal information, such as appointments, contact lists, notes, and reminders, and often integrated with email/messaging systems. Their user interfaces are distinguished by the relative lack of structure to the…

pinned menu

a menu that would normally go away after a selection is made but which stays up because a pushpin icon is clicked which “pins” it up, causing it to remain available after the selection; similar in spirit to tear-off menus.…

pinyin input

Chinese-character input based on the pinyin alphabet. Pinyin is a method of writing Chinese in a roman alphabet. With pinyin input systems, users can type the Chinese words phonetically, and then select among a few alternative Chinese characters that represent…

placard

a rectangular region that can provide status information or controls, generally that apply to the entire document view within a window, such as a magnification percentage displayed at the bottom of a window that can be clicked to choose other…

playability

the degree to which a game is fun to play and usable, with an emphasis on the interaction style and plot-quality of the game; the quality of gameplay.

Playability is affected by the quality of the storyline, responsiveness, pace, usability,…

playtesting

testing of games (including usability testing), examining pace, flow, narrative, controls, entertainment value, appeal for different target populations, challenge, novelty, etc.

plug and play

a hardware architecture that enables users to add and remove input and output devices at any time and immediately use them, without software installation or complicated configuration. The computer system recognizes the devices and configures itself, as with the USB…

pluggable look and feel architecture

an application or system architecture that allows applications to run with a different look and feel than that originally envisioned by the application’s designers. Any other interface specification can be substituted for the same application. While allowing general-purpose substitution of…

pluralistic walkthrough

a method of usability inspection where a diverse group of stakeholders in a design are brought together to review the design, including user interface designers, users, developers, and management. The walkthrough is conducted by identifying primary tasks for the system…

pointer

a small image on the screen (typically an arrow) indicating where the user is currently pointing. The pointer is moved by a pointing device, such as a mouse, a tablet, or a touchpad.

Note: pointers are often mistakenly called “cursors”,…

pointer jumping

when the pointer automatically moves around to the most likely place you’ll want to click next, such as moving the pointer over the default button of a dialog box as soon as the dialog appears. This shortens the average amount…

pointing device

any device used to indicate a position, as a mouse is used to point to a position on a screen. Typical pointing devices include a mouse, pen, lightpen, trackball, touchscreen, touch tablet, touchpad, and possible a joystick or cursor keys.…

polymorphic artifact

a software artifact (application, widget, dialogue) that can adapt its appearance and behavior to suit different users, uses, and technologies (e.g. I/O devices). The adaptation may be at the level of functionality, process of use, or appearance.

popup menu

a menu that appears outside of the menubar and that pops up when a user clicks on it. Popup menus are typically used to contain options (equivalent to a set of radio buttons, but taking less screen real estate) rather…

portal

(web) a website that serves as a central information source, especially by providing substantial numbers of links to other related websites. Portals are distinguished by their topic, method of link selection, and added value, such as reviews, rankings, and site…

portrait and landscape

describes the orientation of a rectangle, a screen, a printout, or any image with unequal length and height. A portrait orientation is taller than it is wide, as would be common for a portrait in a photograph. A landscape orientation…

power law of practice

an expression of time to perform a task based on practice trials, saying that people improve in speed at a decaying exponential rate.

T_n = T₁ n^-a, a ~ 0.4

T_n = the time to perform a task after n…

precision

in information retrieval, a measure of the quality of search results. Precise results have a high proportion of good matches and a low number of false positives (results that really shouldn’t count as matches.

predictive metric

a value describing some aspect of a system that purports to provide a prediction or estimate of the usability of the system. For instance, if we described the font size used on a web page as a predictive metric (e.g.…

prisoner’s dilemma

a classic problem statement describing a situation where what is rational for an individual is in conflict with what is rational for the group (as with the commons problem). This type of problem is useful for describing problems in coordinating…

privacy

the principle of protecting private information about people, especially in shared or collaborative systems, and of helping to keep people free of distractions. Privacy may be provided for security reasons, to keep people (such as celebrities) from being deluged with…

procurement decisionmaker

the person responsible for selecting software to be used in an organization, who will need to have an evaluation of the usability of the software in order to understand its impact on the productivity of the organization.

productivity paradox

why is it that, despite adopting cool new technology, many businesses do not achieve higher productivity? That’s the productivity paradox. The systems were intended to improve productivity, but they didn’t. Why not? In general, it stems from a failure to…

programming by demonstration

systems that allow a person to construct a program simply by demonstrating the actions that the program needs to perform. The system then must infer what loops and conditionals might be involved, and may allow the user to select among…

programming by example

similar to programming by demonstration, a user provides examples of how a program should operate, either by demonstrating the steps or by showing examples of the inputs and outputs, and the system infers a program that would achieve those examples.…

progress indicator

a display showing how far a time-consuming process has gone. A progress bar, for instance, increases in size over time to show what proportion of the total time has already passed. Below is a progress indicator for copying a file.…

progressive disclosure

the design principle that says to show overviews and hide details until the user requests more detail, and then to provide only the additional level of detail required.

This principle is often used in file systems and outlines, as with…

prompt

A message on the computer screen indicating that the computer is ready to accept user input. In a command-line interface, the prompt may be a simple “>” symbol or “READY >” message, after which the user may type a command…

property sheet

a form containing a set of attributes and values for a selected object and allowing those properties to be modified, often displayed as a dialog box or palette. A typical example is a property sheet for text properties, which allows…

proportional scrollbox

a scrollbox that varies in size according to the percentage of the document that is visible.

prototype-instance model

(programming) a version of object-oriented programming that does not have classes. Instead, objects inherit behavior directly from other objects. This dramatically simplifies the language by removing unnecessary concepts such as metaclasses. This approach was popularized by the “Self” language.

(psychology)…

prototyping

the development of incomplete representations of a target system for testing purposes and as a way of understanding the difficulties of development and the scale of the problem.

Prototyping is an essential element of an iterative design approach, where designs…

prototyping theatre

a puppet show approach to prototyping and user testing. User interface elements, such as screens and widgets are held up in the theatre, by hand or with sticks, to demonstrate how the screen works. Multiple puppeteers are needed for complex…

proxemics

issues dealing with spatial relationships between interface components, devices, and users. For instance, the distance between users can determine what communication device is used and what settings are functional (such as volume). Also, the position of devices with respect to…

proxy

a small image that serves as a graphical preview of an operation that will take place on a full image. The proxy usually substitutes a generic shape for the full image or eliminates detail otherwise. Used commonly in dialog boxes…

psychology of programming

PoP; the study of how programmers create software, including such topics as learning a programming language, planning a program, how language features affect coding time and accuracy, and how programmers isolate and repair bugs.

In addition to understanding basic principles…

psychophysics

a discipline of psychology that measures the response characteristics of human perception in a method parallel to measuring the response characteristics of physical materials. The prototypical examples are human perception of the intensity of light and sound. People report the…

publish-subscribe model

a mechanism for sharing data between applications and for workgroup collaboration. Applications can “publish” their data to a file, which will automatically notify all documents that have “subscribed” to that file, and those documents then update to reflect the most…

puck

a hand-held pointing device used in conjunction with an input tablet for precise positioning. A puck may contain crosshairs for aligning the puck position with drawings placed below it.

pulldown menu

a list of options that appears when the user clicks on a menu button (typically in a menubar, but also sometimes a popup menu). Users can then drag their pointer down to select an item in the list, which issues…

pushpin

a pushpin icon at the top of menus and dialogs that, when pinned, keeps them available even after options have been chosen or applied (in the OpenLook graphical user interface). When unpinned, these same menus and dialogs go away after…