Accessibility Glossary

Accessibility Glossary




A hashtag for Twitter users to abbreviate “Accessibility” (#a11y)


A hashtag for Twitter users to abbreviate “Accessibility” (#AxS)


A general term used to describe how easy it is for people to get to, use, and understand things. Accessibility is most often used to describe facilities or amenities to assist people with disabilities, as in “wheelchair accessible.”

This can extend to Braille signage, wheelchair ramps, audio signals at pedestrian crossings, walkway contours, website design and so on.

Accessibility for Ontarians with Disabilities Act, 2005

A statute enacted in 2005 for the purpose of improving accessibility standards for Ontarians with physical and mental disabilities to all public establishments by 2025. The statute is divided into three standards: Customer Service, Harmonized Accessibility (Information & Communications, Employment and Transportation) and Built Environment.

Accessible Design

Comprised of seven principles; Equitable Use, Felxibility in Use, Simple and Intuitive Use, Perceptible Information, Tolerance for Error, Low Physical Effort and Size and Space for Approach and Use. These seven principles when used in conjunction assist designers of housing, commercial and public facilities, outdoor environments, websites, and graphic design elements helpt to improve the access to information and the built environment.

Accessible Form

PDF or HTML based forms that allow users of adaptive technologies to access the information, field elements, and functionality required for completion and submission of the form, including all directions and cues.

Accessible Security

A required permission setting within Adobe Acrobat which preserves the integrity of all document content within a PDF while enabling text access for screen reader or Braille display devices for blind or visually impaired users.

Accessible PDF

A PDF document that has been designed to be accessed by users of adaptive technologies. These accessibility features include: structure tagging, headings, ALT-Text, links, navigation, searchable text, correct reading order, character encodings, accessible forms, tooltips and accessible security.


See Americans with Disabilities Act

Adaptive Technology

An umbrella term that includes assistive, adaptive, and rehabilitative devices for people with disabilities and also includes the process used in selecting, locating, and using them. AT promotes greater independence by enabling people to perform tasks that they were formerly unable to accomplish, or had great difficulty accomplishing, by providing enhancements to or changed methods of interacting with the technology needed to accomplish such tasks.

Adobe Acrobat

A family of application software developed by Adobe Systems Incorporated to view, create, manipulate, print and manage files in Portable Document Format (PDF). All members of the family, except Adobe Reader (formerly Acrobat Reader), are commercial software; Adobe Reader however, is available as freeware and can be downloaded from Adobe's website. Adobe Reader enables users to view and print PDF files but has negligible PDF creation capabilities. Acrobat and Reader are widely used as a way to present information with a fixed layout similar to a paper publication.

Adobe Systems Incorporated

An American computer software company headquartered in San Jose, California, USA. The company has historically focused upon the creation of multimedia and creativity software products, with a more-recent foray towards rich Internet application software development. Popular software titles include: Adobe Acrobat, Adobe Dreamweaver, Adobe Flash, Adobe InDesign, Adobe Illustrator, Adobe LiveCycle, Adobe Photoshop.

Age-Related Macular Degeneration (AMD)

A medical condition which usually affects older adults that results in a loss of vision in the center of the visual field (the macula) because of damage to the retina. It is a major cause of visual impairment in older adults (>50 years).[1] Macular degeneration can make it difficult or impossible to read or recognize faces, although enough peripheral vision remains to allow other activities of daily life.

Age-Related Adaptive Technology

Changes in people's functional ability due to aging can include subtle and/or gradual changes in abilities or a combination of abilities including vision, hearing, dexterity and memory. Any one of these limitations can affect an individual's ability to access Web content.

Ai Squared

Ai Squared has been a leader in the assistive technology field for over 20 years. Thier flagship product, ZoomText, is regarded as the world’s best magnification and reading software for the visually impaired.

Alternative Format

Alternate formats usable by people with disabilities may include, but are not limited to, Braille, ASCII text, large print, recorded audio, and electronic formats that comply with this part.

Alternative Keyboard

Devices which are used by people with certain physical disabilities to simulate the keyboard

Alternative Methods

Different means of providing information, including product documentation, to people with disabilities. Alternate methods may include, but are not limited to, voice, fax, relay service, TTY, Internet posting, captioning, text-to-speech synthesis, and audio description.

Alternative Pointing Device

A device or devices used by people with certain physical disabilities to simulate mouse pointing and button activations.


Refers to “alternative text” that is placed in the code for an image in a PDF document, Microsoft Office or an HTML page (in an ALT tag). If the image is not displayed, the ALT text can be presented instead. ALT text is especially useful to users of speaking browsers. The text should be a brief representation of the purpose of the image, not a description of the image. ALT text is frequently seen on tooltips when users move the mouse over images.

Americans with Disabilities Act (ADA)

A 1990 federal law that forbids discrimination against persons who are disabled. It gives civil rights protection to individuals with disabilities similar to those provided to individuals on the basis of race, color, sex, national origin, age, and religion. It guarantees equal opportunity for individuals with disabilities in public accommodations, employment, transportation, State and local government services, and telecommunications.

Apple Inc.

Established on April 1, 1976 in Cupertino, California, and incorporated January 3, 1977, the company was previously named Apple Computer, Inc., for its first 30 years, but removed the word “Computer” on January 9, 2007, to reflect the company's ongoing expansion into the consumer electronics market in addition to its traditional focus on personal computers.

The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad. Apple software includes the Mac OS X operating system; the iTunes media browser; the iLife suite of multimedia and creativity software; the iWork suite of productivity software; Aperture, a professional photography package; Final Cut Studio, a suite of professional audio and film-industry software products; Logic Studio, a suite of music production tools; and iOS, a mobile operating system.

Assistive Technology

Any item, piece of equipment, or system, whether acquired commercially, modified, or customized, that is commonly used to increase, maintain, or improve functional capabilities of individuals with disabilities.

This definition is very broad, potentially including anything from wheelchairs to hearing aids. In the context of Section 508, the term typically refers to tools used by disabled individuals to increase or improve the functionality of information technology.

Assistive technology can be either software- or hardware-based. Hardware solutions can span a broad range of devices, from low-tech items such as mouth sticks or paper stabilizers, to high-tech products such as refreshable Braille displays or eye gaze communication systems. Software solutions can include built-in features such as the accessibility options in Microsoft Windows or stand-alone programs such as speech recognizers and screen readers. The most appropriate type of assistive technology for a disabled individual depends on the nature of the disability.

Automated Accessibility Checker

A collection of tools that are intended to identify common accessibility problems in PDF documents. These tools can be used as a basic identifying mechanism that will only scan the basic elements within a document. They cannot be used as standalone accessibility verification methods as they do not very usability.

Audio Description

An audio description (also called an “auditory description” in the Web Content Accessibility Guidelines 1.0 [WCAG 1.0]) is either a prerecorded human voice or a synthesized voice (recorded or generated dynamically) describing the key visual elements of a movie or other animation. The audio description is synchronized with (and possibly included as part of) the audio track of the presentation, usually during natural pauses in the audio track. Audio descriptions include information about actions, body language, graphics, and scene changes.


Barrierefreie Informationstechnik-Verordnung (BITV)

An enhancement to the German “Behindertengleichstellungsgesetz.” All regulations apply to Web presences and public accessible services on the internet offered by public authorities. BITV clauses are based on Web Content Accessibility Guidelines 1.0. ( -> see WCAG). BITV goes along with WCAG priorities 1 and 2. Central navigation- and access services even have to fulfill priority 3 requirements


The German law on equality of disabled people and Disability Discrimination Act (BGG) is a discrimination against people with disabilities and eliminate or prevent the equal participation of people with disabilities in the life of society and ensure a self-determined lifestyle allow them.

The law applies primarily to public authorities on the federal level. To implement the same content over the country level are each country's own national equality laws created.


Blindness involves a substantial, uncorrectable loss of vision in both eyes. Blindness can be congenital, or appear later during the lifespan – then caused by accidents, diseases, or the aging process.


A code which enables blind persons to read and write. It was invented by a blind Frenchman, Louis Braille, in 1829. Braille is comprised of a rectangular six-dot cell on its end, with up to 63 possible combinations using one or more of the six dots. Braille is embossed by hand (or with a machine) onto thick paper, and read with the fingers moving across on top of the dots. Combinations of Braille dots within a cell represent contractions of two or more print letters and Braille characters take up three times as much space as print.

Braille Display

Commonly referred to as a “dynamic Braille display,” raises or lowers Braille dot patterns on command from an electronic device, usually a computer. The result is a line of braille that can change from moment to moment. Current dynamic Braille displays range in size from one cell (six or eight dots) to an eighty-cell line, most having between twelve and twenty cells per line.

Braille Keyboard

A keyboard with Braille-coded keys. For example, transparent Braille labels allow both blind and sighted users to access a keyboard.

Browser (for Non-Visual Output)

Blind and partially sighted individuals will use one of three possible methods to read pages on the World Wide Web. Users with some sight can use screen magnification software. For users with little or no useful sight, the options are Speech Synthesizers or sound cards to convert text into speech or a refreshable Braille display to convert text into Braille.


A software application that is used by an end user to access a website. The most popular browsers include Microsoft® Internet Explorer, Google Chrome, Apple Safari and Mozilla Firefox.



Text equivalents for movie audio. Captions consist of a text transcript of the auditory track of the movie (or other video presentation) that is syncronized with the video and auditory tracks. Captions are generally rendered graphically and benefit people who can see but are deaf, hard-of-hearing and anyone who cannot hear the audio (e.g. someone in a noisy environment). Captions are generally graphically super imposed (“on top of”) the syncronized visual track.

Cascading Style Sheets (CSS)

Style sheets describe how documents are presented on screens, in print, and even in spoken voice. Style sheets allow the user to change the appearance of hundreds of Web pages by changing just one file. A style sheet is made up of rules that tell a browser how to present a document. Numerous properties may be defined for an element; each property is given a value.

Cognitive Disabilities

People with cognitive disabilities may have trouble reading, for example Auditory Processing Deficits and Attention Deficit Disorders.

Cognitive Impairments

See Cognitive Disabilites

Collated Text Transcript

A collated text transcript is a text equivalents of a movie or animation. More specifically, it is the combination of the text transcript of the audio track and the text equivalent of the visual track.

Colour Blindness/Deficiencies

Color blindness is a lack of sensitivity to certain colors. Common forms of color blindness include difficulty distinguishing between red and green, or between yellow and blue. Sometimes color blindness results in the inability to perceive any color.


The retina in our eyes contains two basic types of light sensors (photoreceptors), cones and Rods, which form independent visual systems that are dedicated to special tasks. Cones are primarily used for color and daylight vision.


Content may include, among other things: text, images, sounds, videos, downloadable information and animations.

Content Accessibility

The usage of techniques to enable people with disabilities to access websites, PDF documents and all other electronic information. These techniques can include the labelling of elements to assist with navigating headings, links, text, images and tables.


Context is a fundamental requirement to improve the ease of understanding for adaptive technology users. Conveying author intent by ensuring the reading order relays information as easily as possible for the audience.


A difference in visual attributes (e.g., hue, lightness, saturation) of an object's foreground and background.

Conversion Tool

A “conversion tool” is any application or application feature (e.g., “Save as PDF”) that transforms convent in one format to another format (such as a markup language). Features can also include any automatic functions that are designed to add accessibility features such as document tags for HTML or PDF. These conversion tools very rarely are capable of adding true accessibility.


Data Cell

A table element that contains text, numbers or data. Also see Table Data Cell.


See Disability Discrimination Act


For blind users and users with visual impairments, textual descriptions, also called Text Equivalents, can be provided that are read aloud by a Screen Reader. Text descriptions can be provided for user iterface elements, such as controls, as well as for images and animation (required by Section 508 and the Web Content Accessibility Guidelines).

When using images, graphical representations of text, frames, image maps, applets, or animation, you can also use the alt attribute for this purpose. If necessary, as in the case of complex graphics, also maintain a long description in the longdesc attribute. This description refers to a URL that leads to further information about the element.

Design for All

A design philosophy, which aims to improve the life of everyone through design. (From

Designer PDF

See Dynamic PDF Form


People with malfunctioning in the green Cone system, that is, with only one malfunctioning cone system (Dichromats). Green cannot be distinguished from certain combinations of red and blue; this is the most common type of color deficiency.

Device Dependant

Used to describe event handlers that require a specific kind of input device. For example, onDblClick requires a mouse; there is no keyboard equivalent for double clicking. Input devices may include pointing devices (such as the mouse), keyboards, Braille devices, head wands, microphones, and others. Output devices may include monitors, speech synthesizers, and Braille devices. Scripting should be device-independent or provide multiple input and output options for different devices.

Device Independent

Users must be able to interact with a (and the document it renders) using the supported input and output devices of their choice and according to their needs. Input devices may include pointing devices, keyboards, braille devices, head wands, microphones, and others. Output devices may include monitors, speech synthesizers, and braille devices.


People with only one malfunctioning Cone system can have the following impairments:

Protanopia: Malfunctioning in the red cone system; typically only two (yellow, blue) or three colors (yellow, blue, purple) can be distinguished – yellow comprises red, orange, yellow, and green, blue coincides with blue and purple

Deuteranopia: Malfunctioning in the green cone system; green cannot be distinguished from certain combinations of red and blue; this is the most common type of color deficiency

Tritanopia: Malfunctioning of the blue cone system; longer wavelengths appear as red and the shorter ones as bluish-green; this color deficiency is very rare

Digital Signature

A method of security and document integrity which includes a very large number created in such a way that it can be shown to have been done only by somebody in possession of a secret key and only by processing a document with a particular content. It can be used for the same purposes as a person's handwritten signature on a physical document. It can also be used to legally bind a document.

Diminished Mobility

Some people suffer from decreased mobility. This can range from stiffness of fingers due to arthritis to complete paralysis below the neck. People suffering from diminished mobility will often require different adaptive technologies to effectively interact with electronic content. Different devices may include; speech synthesizers, head wands and sip and puff controls.


A condition that curtails to some degree a person's ability to carry on his normal pursuits. A disability may be partial or total, and temporary or permanent.

Disability Discrimination Act (DDA)

A name shared by two laws passed in Australia (1992) and the United Kingdom (1995). They both prohibit discrimination against people with disabilities.

Disability Discrimination Act (Australia - 1992)

The objectives of the Disability Discrimination Act 1992 (DDA) are “to eliminate, as far as possible, discrimination against persons on the ground of disability in the areas of: work, accommodation, education, access to premises, clubs and sport; and the provision of goods, facilities, services and land; and existing laws; and the administration of Commonwealth laws and programs; and to ensure, as far as practicable, that persons with disabilities have the same rights to equality before the law as the rest of the community; and to promote recognition and acceptance within the community of the principle that persons with disabilities have the same fundamental rights as the rest of the community.”

Disability Discrimination Act (United Kingdom - 1995)

The Disability Discrimination Act 1995 (DDA) is “an Act to make it unlawful to discriminate against disabled persons in connection with employment, the provision of goods, facilities and services or the disposal or management of premises; to make provision about the employment of disabled persons; and to establish a National Disability Council.”


A digital representation of a body of information designed with the capacity (and usually intent) to communicate. Most common formats include those created by the Microsoft Office Suite (Word, PowerPoint and Excel), OpenOffice (Writer, Impress and Calc) or Apple's iWork Suite (Pages, Numbers and Keynote).

Document Structure

The tree of elements encoded in the source document. Each element in this tree has exactly one parent, with the exception of the root element, which has none. This creates order to assist with context and accessibility.

Dynamic Content

Content that is generated in response to a request. This may be used for content that depends on changing environmental factors such as time (e.g., stock quotes) or place (e.g., nearby gas stations). Dynamic content can often cause accessibility challenges for users of adaptive technologies.

Dynamic Form

Dynamic forms generate new fillable boxes based on previous responses by a user. Dynamic forms can often cause accessibility challenges for users of adaptive technologies.

Dynamic PDF Form

Dynamic PDF forms are capable of rendering, or displaying, content as a user selects or fills in information in particular form fields. To support their LiveCycle range of server products, Adobe Systems provides an XFA forms editor with Adobe Acrobat Professional called Acrobat Designer. Because they use a different technology than traditional PDF, forms produced by Acrobat Designer are said to be “Designer PDFs”, or “XFA PDFs” Dynamic PDF forms are often regarded as more difficult to employ accessibility techniques.


The selective impairment of reading skills despite normal intelligence, sensory acuity, and instruction (also called developmental dyslexia). Several perceptual studies have suggested that dyslexis subjects process visual information more slowly than normal subjects. Such visual abnormalities were reported to be found in more than 75% of the reading-disabled children tested. Therefore, it is important to rule out problems with sensory acuity (including visual acuity and visual processing) before labelling an individual as truly dyslexic.


Ease of Navigation

The ease a user should be able to read and browse your electronic documents and websites and obtain information with minimum effort. Both structure and visitor comprehension are contributing factors to the ease of navigation.

Electronic Document

An electronic representation of a page-oriented compilation of text, images and graphic data, as well as metadata that helps to identify, understand and display the data. Electronic documents can be reproduced on paper or displayed on screen without any significant loss of information.

Electronic Document Accessibility

Using techniques to provide navigation and context to electronic documents to enable users of adaptive technologies to easily read the included content.

End User

An individual who is the target audience of a website, electronic document or communication. In the context of accessibility, end user is often synonymous with a user of adaptive technologies or a person with disability.


Content is “equivalent” to other content when both fulfill essentially the same function or purpose upon to the user. The equivalent must fulfill essentially the same function for the person with a disability (at least insofar as is feasible, given the nature of the disability and the state of technology), as the primary content does for the person without any disability.

Since text content can be presented to the user as synthesized speech, braille, and visually-displayed text, these guidelines require text equivalents for graphic and audio information. Text equivalents must be written so that they convey all essential content. Non-text equivalents (e.g., an auditory description of a visual presentation, a video of a person telling a story using sign language as an equivalent for a written story, etc.) also improve accessibility for people who cannot access visual information or written text, including many individuals with blindness, cognitive disabilities, learning disabilities, and deafness.

Equivalent information may be provided in a number of ways, including through attributes (e.g., a text value for the “alt” attribute in HTML and SMIL), as part of element content (e.g., the OBJECT in HTML), as part of the document's prose, or via a linked document (e.g., designated by the “longdesc” attribute in HTML or a description link). Depending on the complexity of the equivalent, it may be necessary to combine techniques (e.g., use “alt” for an abbreviated equivalent, useful to familiar readers, in addition to “longdesc” for a link to more complete information, useful to first-time readers).


Fillable Form

An electronic document or web page that allows a user to input and save information to be sent to and collected by a second party.


Commonly identifies the look of text in a document or web page. Formally, font identifies collections of graphics that can be glyphs or other graphic elements according to ISO 15930-4.

A font file defines how glyphs are displayed. If a font file is contained in a PDF file then the associated font is embedded in the file. If the font does not contain a complete character set but, for example, only the glyphs of the characters used in the document, the term used is subsetted font.


See Fillable Form

Form Field

A form field is a particular box within a fillable form that requests specific information. Examples can include; Name, Address, Phone Number, Multi-line text Boxes, Radio Buttons, Check Boxes, and/or Signature fields.


The result of input or selecting an object within a Dynamic PDF/XFA or webpage.



See Graphics Interchange Format


A Neural-Related Impairment, is often caused when the fluid in the eye does not drain away fast enough. The built up pressure damages the optic nerve and prevents visual information from reaching the brain. Glaucoma typically affects peripheral vision first (Tunnel Vision), and can cause total blindness if not treated at an early stage.

Gnome Onscreen Keyboard (GOK)

An application that displays a dynamically changing keyboard on the screen and allows multiple input methods for selection. GOK uses the AT-SPI protocol for updating the keys within the keyboard.


Two- or three-dimensional images, typically drawings or photographs. See also GIF, JPEG, PNG, SVG, and VRML.

Graphical User Interface (GUI)

A graphical user interface (GUI), pronounced G-U-I, is a type of user interface that allows users to interact with programs in more ways than typing such as computers; hand-held devices such as MP3 players, portable media players or gaming devices; household appliances and office equipment with images rather than text commands. A GUI offers graphical icons, and visual indicators, as opposed to text-based interfaces, typed command labels or text navigation to fully represent the information and actions available to a user. The actions are usually performed through direct manipulation of the graphical elements.

The term GUI is historically restricted to the scope of two-dimensional display screens with display resolutions capable of describing generic information, in the tradition of the computer science research at the Palo Alto Research Center (PARC). The term GUI earlier might have been applicable to other high-resolution types of interfaces that are non-generic, such as videogames, or not restricted to flat screens, like volumetric displays.

Graphics Interchange Format (GIF)

The Graphics Interchange Format (GIF) is a bitmap image format that was introduced by CompuServe in 1987 and has since come into widespread usage on the World Wide Web due to its wide support and portability.


Head Pointer

A device attached to the user's head that allows a user to move the pointer on the screen, (usually moved by the mouse, a pointing device, the arrow keys, or with the movement of their head). It is useful for people who have limited mobility.

Heading Tag

In PDF and HTML, Heading Tags are used as structural navigation aids to help identify the order of content. Within PDF, Adaptive Technologies are able to search through the document for Heading Tags (H1, H2, H3, H4, H5, H6) that assists with skimming a document. Of note, most document design should attempt to minimize the number of Heading Tag levels beyong Heading Tag Three (H3) as many screen reader users are not anticipating that many levels.

Hearing Impairments

People with these impairments may be completely deaf, or may have partial loss of hearing.


A pointer within a hypertext document which points (links) to another document, which may or may not also be a hypertext document. Within a PDF, screen readers will identify this element if tagged properly by auditorily reading “Link”.

Hypertext Markup Language (HTML)

A markup language that is used on most of the World Wide Web to create Web pages. The standards for HTML are controlled by the W3C.

HTML has also been a prefered method of reading content by adaptive technology users because of its inherent content structures, however a properly tagged PDF will provide the same rich user experience.


The eye is very sensitive to restriction of its supply of oxygen. A dimming of vision (a brownout or greyout) accompanied by loss of peripheral perception may result from low blood pressure, shock, g-LOC (an aviation related problem) or simply standing up suddenly, especially if sick or otherwise infirm. Vision usually returns readily once the conditions restricting blood flow are lifted.



Images and photographs of physical objects, paintings, prints, drawings, other images and graphics, animations and moving pictures, film, diagrams, maps, musical notation.

Image Maps

Areas of an image on a web page or Dynamic PDF that have links to other areas of the Web. Some types of images map can have ALT tags on the areas, while others must have text links.

  • Visual Impairments: People with visual impairments range from the totally blind to people who have some difficulty reading small print
  • Hearing Impairments: Hearing-impaired people may be completely deaf, or may have partial loss of hearing.
  • Diminished Mobility: Some people suffer from decreased mobility. This can range from stiffness of fingers due to arthritis to complete paralysis below the neck.
  • Cognitive Disabilites: People with cognitive disabilities may have trouble reading

In the context of electronic documents and/or websites, inaccessible pertains to the difficulties an end user may face when trying to access content.

Structuring that can lead to inaccessibility may include among other things: lack of keyboard navigation, the requiring of the use of a mouse, small text, overlapping text, low contrast colour combinations, a lack of ALT-Text, distracting animations or the lack of captions.

Information and Communications Technologies (ICT)

A generic name for all of the technologies involved with communicating with computers.

Information Architecture

Covers the navigation structure, organization, and labeling of information.

Input Method

The way an end user interacts with and is able to insert content on a computer. Traditional methods will include a keyboard and mouse, while less traditional methods can include; speech-to-text, sip-and-puff straws, joystick control, head pointers, touch screens or motion capture devices.

Integrity of Content

Due to complex graphic design and the layering of visual elements such as shading, effective accessibility tagging and structures should maintain the original look and feel of the presented content, particularly in PDF format.

Interactive Elements

An interactive element is piece of content that, by specification, may have associated behaviors to be executed or carried out as a result of user or programmatic interaction. Interactive elements can include: links, image maps, form elements, elements with a value for the longdesc attribute, and elements with event handlers explicitly associated with them (e.g., through the various “on” attributes).


A point of interaction between components, and is applicable at the level of both hardware and software. This allows a component, whether a piece of hardware such as a graphics card or a piece of software such as an internet browser, to function independently while using interfaces to communicate with other components via an input/output system and an associated protocol.

In addition to hardware and software interfaces, a computing interface may refer to the means of communication between the computer and the user by means of peripheral devices such a monitor or a keyboard, an interface with the internet via Internet Protocol, and any other point of communication involving a computer.


The ability of software and hardware on multiple machines from multiple vendors to communicate meaningfully. Ensuring cross-platform interoperability is critical to the success of an accessibility strategy.

International Standards Organization (ISO)

Widely known as ISO, is an international-standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary industrial and commercial standards. It has its headquarters in Geneva, Switzerland. While ISO defines itself as a non-governmental organization, its ability to set standards that often become law, either through treaties or national standards, makes it more powerful than most non-governmental organizations. In practice, ISO acts as a consortium with strong links to governments.


A worldwide computer network using the TCP/IP protocols (and other protocols like HTTP on top of it). The World Wide Web, for example uses HTTP (Hypetext transmission protocol).

ISO 14289-1


ISO 15929


ISO 15930


ISO 19005


ISO 24517


ISO 32000

See PDF 1.7



An object-oriented programming language developed by Sun Microsystems expressly designed for use in the distributed environment of the Internet. It was designed to have the “look and feel” and object-oriented style of the C++ language, but it is simpler to use than C++. Java can be used to create complete applications that may run on a single computer or be distributed among servers and clients in a network. It can also be used to build a small application module or applet for use as part of a Web page.


A compact, object-based client-side scripting language (interpreted by the web browser) for developing client and server Internet applications. It has been originally developed by Netscape. JavaScript is an integral part of PDF Form functionality. Its usage is mainly optimization of static PDF documents or web pages for greater flexibility and more dynamic behaviour.


JAWS (an acronym for Job Access With Speech) is a screen reader, a software program for visually impaired users, produced by the Blind and Low Vision Group at Freedom Scientific of St. Petersburg, Florida, USA. Its purpose is to make personal computers using Microsoft Windows accessible to blind and visually impaired users. It accomplishes this by providing the user with access to the information displayed on the screen via text-to-speech or by means of a Braille display and allows for comprehensive keyboard interaction with the computer.

It also allows users to create custom scripts using the JAWS Scripting Language, which can alter the amount and type of information which is presented by applications, and ultimately makes programs that were not designed for accessibility (such as programs that do not use standard Windows controls) usable through JAWS.

JAWS Scripting Language

JAWS Scripting Language is a proprietary programming language that facilitates the interoperability of the JAWS for Windows screen reading program with practically any application–both proprietary and off-the-shelf. The JAWS Scripting Language, or JSL is a compiled language, allowing for source code protection. “JAWS scripting” commonly also cumulatively refers to customization of JAWS through use of its built-in, user-editable utilities (called “Managers”) or editing the configuration files directly, in combination with writing actual scripts. The scripting language is an API that exposes functionality including a combination of traditional JAWS scripting, MSAA Server direct scripting, and document object model scripting to ensure optimal performance of JAWS to end-users.

Joint Photographic Experts Group (JPEG)

The name “JPEG” stands for Joint Photographic Experts Group, the name of the committee that created the JPEG standard and also other standards. It is one of two sub-groups of ISO/IEC Joint Technical Committee 1, Subcommittee 29, Working Group 1 (ISO/IEC JTC 1/SC 29/WG 1) – titled as Coding of still pictures. The group was organized in 1986, issuing the first JPEG standard in 1992, which was approved in September 1992 as ITU-T Recommendation T.81 and in 1994 as ISO/IEC 10918-1.



A hardware device consisting of a number of mechanical buttons (keys) that the user presses to input characters to a computer. Note that a logical keyboard may provide a representation of keys (e.g., on-screen keyboard) or it may not (e.g., voice recognition).

Keyboard Access

The most important accessibility feature to be provided for Web pages. It allows users to access each “active” element in the portal with the keyboard. Keyboard accessibility is especially important for physically impaired and blind users who cannot use the mouse. All other users will appreciate this feature, too, especially advanced users who enter mass data, or users who work with a laptop.

Keyboard Equivalents

Keys or key combinations that provide access to keyboard functions that are usually activated by a pointing device, voice input, or other input or control mechanisms/devices.

Keyboard Focus

The current assignment of the input from the keyboard or equivalent to a user interface object (a window or an object within a window). For a window, focus is indicated by a focus indicator; for an individual object, focus is indicated by a focus cursor.



Most Web application pages contain forms that consist of labels and input elements, such as input fields. The labels are simple text elements that describe the input elements. With HTML 3.2 the W3C introduced a special label element to be used in this case. This new element offers the advantage that an input field and its label are directly connected. The label's attribute for establishes the connection. Screen readers will then be able to read the correct label whenever an input element gets the focus.


Layers in PDFs are just like layers in InDesign and QuarkXPress and like top level layers in Illustrator and Photoshop. Each layer may hold any portion of the document's objects, and layers may be made visible or invisible, showing or hiding their contained objects, in any combination. Layers can cause significant display issues if not properly addressed during the accessibility process.

Learning Disabilities

A generic term that refers to a heterogeneous group of disorders manifested by significant difficulties in the acquisition and use of listening, speaking, reading, writing, reasoning or mathematical abilities. These disorders are intrinsic to the individual and presumed to be due to Central Nervous System Dysfunction. Even though a learning disability may occur concomitantly with other handicapping conditions (e.g. sensory impairment, mental retardation, social and emotional disturbance) or environmental influences (e.g. cultural differences, insufficient/inappropriate instruction, psychogenic factors) it is not the direct result of those condition or influences.

Legacy PDF

Any PDF document that has been published or scanned as a PDF that has not been made accessible, or tagged.


See Hyperlink


Table rendering process used by some screen readers and text browsers that converts table cells into a series of paragraphs that will be read one after the other in the order they are defined in the PDF or HTML code.

Linearized Table

A table that has been subjected to linearization. Depending on page layout, some PDFs or Web pages may be extremely hard to decipher after their tables have been linearized.

Low Vision

A Visual Impairment, not corrected by standard eyeglasses, contact lenses, medication, or surgery, that interferes with the ability to perform everyday activities.


Lynx was a product of the Distributed Computing Group within Academic Computing Services of the University of Kansas, and was initially developed in 1992 by a team of students at the university (Lou Montulli, Michael Grobe and Charles Rezac) as a hypertext browser used solely to distribute campus information as part of a Campus-Wide Information Server and for browsing the Gopher space. Beta availability was announced to Usenet on 22 July 1992. In 1993 Montulli added an Internet interface and released a new version (2.0) of the browser.

Because of its text-to-speech–friendly interface, Lynx was once popular with visually impaired users, but better screen readers have reduced the appeal of this application.


Macular Degeneration

Belongs to the Receptor-Related Impairments and is damage to or breakdown of the macula and thus a loss of the central vision. Color vision may also be diminished, although peripheral vision and night vision usually remain unaffected.

Macular degeneration may be the result of aging processes in the eye (age-related maculopathy, ARM, also called senile macular degeneration); there are also some other forms of macular degeneration, which are inherited and not associated with aging.


An application developed by Ai Squared that enlarges and enhances everything on a user's computer screen.


An application developed by Ai Squared that both larges and enhances what is displayed on a user's computer screen combined with a screen reader that uses a voice synthesizer to read screen content aloud.


Is a container element which can contain graphics elements or other container elements which define a set of graphics that is to be used as a semi-transparent mask for compositing foreground objects into the current background.

Media Opacity

Opacities of the clear refractive media of the eye such as the cornea, anterior chamber, lens, and vitreous humor may cause acute visual loss as manifested by blurry vision or reduced visual acuity. While pupillary reflexes may be affected, these conditions generally do not cause a relative afferent pupillary defect.

Causes of media opacity include corneal edema, hyphema, cataract and vitreous hemorrhage.

Memory Impairments

Individuals with memory impairments may have problems with short-term memory, missing long-term memory, or some loss of language.

Mental Health Disabilities

Individuals with mental or emotional disabilities may have difficulty focusing on information on a Web site, or difficulty with blurred vision or hand tremors due to side effects from medications.


Data about authoring information in electronic documents or on the Web, including but not limited to authorship, classification, endorsement, policy, distribution terms, IPR, and so on. Effective metadata can assist with search engine optimization.

Microsoft Corporation

Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions. Established on April 4, 1975 to develop and sell BASIC interpreters for the Altair 8800, Microsoft rose to dominate the home computer operating system (OS) market with MS-DOS in the mid-1980s, followed by the Microsoft Windows line of OSs. Microsoft would also come to dominate the office suite market with Microsoft Office.

Mobility Impairments

Physical impairments that limit movement and fine motor controls like walking, lifting, or using a mouse or keyboard. People with physical impairments often require adaptive or assistive technologies to use computers or navigate through electronic documents or Web sites.


People with two or three malfunctioning Cone systems can be assigned to the following two types:

Monochromats I: People with no functioning cones; people with this deficiency have the following problems:

  • Lack of color vision – the Rods can distinguish only levels of gray (analog to black-and-white images)
  • Day-blindness – the daylight is too bright for them (and the rod system) and causes pain
  • Low visual acuity – the area of highest sensor density, the fovea, contains no rods

Monochromats II: People with only one variety of the cones functioning in addition to the rods. These people also see colors only as variations in intensity, that is analog to unicolored images


A Microsoft technology (Microsoft® Active Accessibility®, MSAA) available as an add-on since Windows 95 and built into subsequent Windows releases that provides a standard, consistent mechanism for exchanging information between applications and assistive technologies. For example, MSAA allows applications to expose screen readers to the type, name, location, and current state of all objects and notifies screen readers of any Windows event that leads to a user interface change.


Neural Related Impairments

There a two types of neural-related visual impairments:

Night Blindness

Belongs to the Receptor-Related Impairments and is a lack of the ability to see at night. It sets in if light intensity goes below a certain level, for example, at the twilight level.

Night-blindness is caused by malfunctions of the Rod system. The Cone system alone is not sensitive enough for night vision (cones comprise only about 1/25 of the number of rods). The rods may be affected in many ways, one common example is a breakdown of the pigments (retinitis pigmentosa).

Non-Text Equivalent

Content provided through audio files, sign language, or other visual means to convey information to people with visual or cognitive disabilities.

NonVisual Desktop Access (NVDA)

NonVisual Desktop Access (NVDA) is a free and open source screen reader for the Microsoft Windows operating system. Providing feedback via synthetic speech and Braille, it enables blind or vision impaired people to access computers running Windows for no more cost than a sighted person. Major features include support for over 20 languages and the ability to run entirely from a USB drive with no installation.



A basic data structure used to construct PDF files. An object can be of the following types: array, Boolean, dictionary, integer, null, real, datastream or string.

On-Screen Keyboard

A keyboard that appears on screen so a user who cannot use their hands can use Assistive Technology (such as a Head Pointer) to enter keyboard input.

Open Source

Open source software is a licensing model for software which gives free access to the source code of the software to allow interested parties to modify or contribute to the software as they see fit. Commonly created as collaborative projects and shared at no cost.

Operating Environment

The term “operating environment” refers to the environment that governs the user agent's operation, whether it is an operating system or a programming language environment such as Java.

Operating System

An operating system (OS) is software, consisting of programs and data, that runs on computers and manages computer hardware resources[1] and provides common services for efficient execution of various application software.

Optical Character Recognition (OCR)

The process of reading printed, typed or handwritten text (usually by scanning) and translating it into an electronic format that can be manipulated by a computer. This is a function within Adobe Acrobat that can permit accessibility for scanned documents

Optic Nerve Disease

Diseases which affect the optic nerve may cause acute visual loss. Signs include an abnormal pupillary reflex, with an afferent pupillary defect when the optic nerve disease is unilateral. It can also be caused by strobe light.

The optic nerve can be affected by many diseases including optic neuritis, retrobulbar neuritis, papillitis, papilledema, glaucoma, ischemic optic neuropathy, and giant cell arteritis.


Optics is part of everyday life. The ubiquity of visual systems in biology indicate the central role optics plays as the science of one of the five senses. Many people benefit from eyeglasses or contact lenses, and optics are integral to the functioning of many consumer goods including cameras. Rainbows and mirages are examples of optical phenomena. Optical communication provides the backbone for both the Internet and modern telephony.


See Linearization



The process of dividing information (content) into discrete pages, either electronic pages or printed pages. Today the latter are usually simply instances of the former that have been outputted to a printing device, such as a desktop printer or a modern printing press. For example, printed books and magazines are created first as electronic files (for example, PDF or QXD files) and then printed.

Pagination encompasses rules and algorithms for deciding where page breaks will fall, which depends on semantic or cultural senses of which content belongs on the same page with related content and thus should not fall to another (e.g., widows and orphans). Pagination is sometimes a part of page layout, and other times is merely a process of arbitrary fragmentation.


See Portable Document Format

PDF 1.7

The final revised documentation for PDF 1.7 was approved by ISO Technical Committee 171 in January 2008 and published as ISO 32000-1:2008 on July 1, 2008. PDF is now a published ISO standard, titled Document management—Portable document format—Part 1: PDF 1.7.

ISO 32000-1:2008 is the first ISO standard for the full function PDF. The previous ISO PDF standards (PDF/A, PDF/X, etc.) are for more specialized uses. The ISO 32000-1 includes all of the functionality previously documented in the Adobe PDF Specifications for versions 1.0 through 1.6, but it should be noted that where Adobe removed certain features of PDF from their standard, they too are not contained in PDF 1.7.

ISO 32000 document was prepared by Adobe Systems Incorporated based upon PDF Reference, sixth edition, Adobe Portable Document Format version 1.7, November 2006. It was reviewed, edited and adopted, under a special fast-track procedure, by ISO Technical Committee 171 (ISO/TC 171), Document management application, Subcommittee SC 2, Application issues, in parallel with its approval by the ISO member bodies.

According to the ISO PDF standard abstract:

ISO 32000-1:2008 specifies a digital form for representing electronic documents to enable users to exchange and view electronic documents independent of the environment in which they were created or the environment in which they are viewed or printed. It is intended for the developer of software that creates PDF files (conforming writers), software that reads existing PDF files and interprets their contents for display and interaction (conforming readers) and PDF products that read and/or write PDF files for a variety of other purposes (conforming products).


PDF/A is a file format for the long-term archiving of electronic documents. It is based on the PDF Reference Version 1.4 from Adobe Systems Inc. (implemented in Adobe Acrobat 5 and latest versions) and is defined by ISO 19005-1:2005, an ISO Standard that was published on October 1, 2005:

Document Management - Electronic document file format for long term preservation

- Part 1: Use of PDF 1.4 (PDF/A-1)

A new version of PDF/A based on PDF 1.7 - ISO 32000-1 is currently under development (ISO/DIS 19005-2).

PDF/A is in fact a subset of PDF, obtained by leaving out PDF features not suited to long-term archiving. This is similar to the definition of the PDF/X subset for the printing and graphic arts.

In addition, the standard places requirements on software products that read PDF/A files. A “conforming reader” must follow certain rules including following color management guidelines, using embedded fonts for rendering, and making annotation content available to users.


ISO 24517-1:2008 is an ISO Standard that was published in 2007.

Document management -- Engineering document format using PDF -- Part 1: Use of PDF 1.6 (PDF/E-1)

This standard defines a format (PDF/E) for the creation of documents used in engineering workflows and is based on the PDF Reference version 1.6 from Adobe Systems.

PDF/E is a subset of PDF, designed to be an open and neutral exchange format for engineering and technical documentation.


PDF/UA (PDF/Universal Accessibility) is a Standards Committee formed by AIIM.

The mission of PDF/UA is to develop technical and other standards for the authoring, remediation and validation of PDF content to ensure accessibility for people that use assistive technology such as screen readers for users who are blind.

As of November 2010, PDF/UA is a “Draft International Standard”: ISO/DIS 14289-1. The PDF/UA wiki, operated by AIIM, contains agendas, meeting-minutes and public-access documents pertaining to PDF/UA and the other PDF International Standards.

The International Committee for ISO/DIS 14289-1 Project Leader is Cherie Ekholm of Microsoft.

The U.S. Committee for ISO/DIS 14289-1 is chaired by Duff Johnson, CEO of Appligent Document Solutions.


PDF/X is an umbrella term for several ISO standards that define a subset of the PDF standard. The purpose of PDF/X is to facilitate graphics exchange, and it therefore has a series of printing related requirements, which do not apply to standard PDF files. For example, in PDF/X-1a all fonts need to be embedded and all images need to be CMYK or spot colors. PDF/X-3 accepts calibrated RGB and CIELAB colors, while retaining most of the other restrictions of PDF/X-1a.

PDF/X files must not only follow certain restrictions, they also must contain a special file identification, inside the PDF, which says which PDF/X version they are. This means that a file can only conform to a single specific PDF/X standard, even if all other requirements are met. The printing conditions or output intent need to be specified in the file. This can be specified in the form of standard profiles using codes, like “CGATS TR 001 SWOP”.

In a PDF/X file that has color managed data each color managed graphic gets its own color profile, so even though the file as a whole is CMYK, individual graphics may be RGB (with calibration information).

Various boxes must be defined. The MediaBox which defines the size of the entire document, either the ArtBox or the TrimBox, which define the extent of the printable area. If the file is to be printed with bleed, a BleedBox, which must be larger than the TrimBox/ArtBox, but smaller than the MediaBox, must be defined.

Active content is not allowed in a PDF/X file. This means that standard PDF features like forms, signatures, comments and embedded sounds and movies are not allowed in PDF/X. Features that are forbidden in the PDF/X standard can sometimes be used, if they do not affect the rendering of the file. This allows for things like annotations outside of the BleedBox.

PDF Reference

The PDF Reference was first published by Adobe in June 1993. In July, 2008, the PDF Reference became ISO 32000.

Personal Information Protection and Electronic Documents Act, 2000

The Personal Information Protection and Electronic Documents Act (abbreviated PIPEDA or PIPED Act) is a Canadian law relating to data privacy. It governs how private-sector organizations collect, use and disclose personal information in the course of commercial business. In addition, the Act contains various provisions to facilitate the use of electronic documents.

PIPEDA became law on 13 April 2000 to promote consumer trust in electronic commerce. The act was also intended to reassure the European Union that the Canadian privacy law was adequate to protect the personal information of European citizens.

Personally Identifiable Information

Any information relating to an identified or identifiable individual.

Photosensitive Epilepsy, Photoepilepsy

Some people with epilepsy can be triggered into seizures by flashing or flickering lights, rapidly changing images or visual patterns. This is called photosensitive epilepsy. When given an EEG test, the majority of people with photosensitive epilepsy will show epileptic discharges in the brain when exposed to flashing lights.

Epilepsy is best described as a tendency to recurrent convulsions. Photosensitivity is sensitivity to flickering or intermittent light stimulation but includes sensitivity to visual patterns. Photosensitive epilepsy therefore can be defined as recurrent convulsions precipitated by visual stimuli, particularly flickering light (Harding & Jeavons, 1994).

Photosensitive epilepsy is largely genetically determined, although its inheritance is complex. It most commonly affects children, and usually appears between the ages of 8 and 20 years. The incidence is highest around ages 12 and 13, suggesting a link with early puberty, and girls are affected more often than boys. One quarter of patients lose their photosensitivity around 25 years of age. The rest remain photosensitive for life.

Physical Disability

Any disabilities that relate to motor disabilities (an individual's ability to control one's motor skills; physical core or extremities). Also see Speech Disabilities.

Plain Text or Plaintext

Any data that is saved as a .txt file format that has had all formatting removed from the content. Plaintext is also data that is input to and transformed by an encryption process, or that is output by a decryption process.


A module (either hardware or software) that adds a special feature to a larger system or program. For example, a program to allow a browser to play movies or to display Flash content.

Portable Document Format (PDF)

Developed by Adobe Systems, Inc., as a way to publish documents electronically, with good formatting for printing, and document security (documents are generally read only). Originally, it was in an image format, and this presented major accessiblity issues. Recently however, Adobe has made large strides in making the PDF format accessible to people with disabilties.

Portable Network Graphics (PNG)

Portable Network Graphics (PNG, pronounced “ping”) is a bitmapped image format that employs lossless data compression. PNG was created to improve upon and replace GIF (Graphics Interchange Format) as an image-file format not requiring a patent license. The PNG acronym is optionally recursive, unofficially standing for PNG's Not GIF.

PNG supports palette-based images (with palettes of 24-bit RGB or 32-bit RGBA colors), grayscale images (with or without alpha channel), and RGB[A] images (with or without alpha channel). PNG was designed for transferring images on the Internet, not for print graphics, and therefore does not support non-RGB color spaces such as CMYK.

PNG files nearly always use file extension “PNG” or “png” and are assigned MIME media type “image/png”; it was approved for this use by the Internet Engineering Steering Group on October 14, 1996.


Postscript is a page description language developed by Adobe Systems, Inc.


People with malfunctioning in the red Cone system, that is, with only one malfunctioning cone system (Dichromats). Typically only two (yellow, blue) or three colors (yellow, blue, purple) can be distinguished – yellow comprises red, orange, yellow, and green, blue coincides with blue and purple.

Public key is also known as public-private key. A cryptographic algorithm which uses two different keys to encrypt and decrypt information. Data encrypted using one key can be decrypted using the other key. The mechanism works in reverse as well.

Typically, one key is kept private; while the other key is distributed to the public.



When a web page is requested via the Hypertext Transfer Protocol, the server locates a file in its file system based on the requested URL. This file may be a regular file or a program. In the second case, the server may (depending on its configuration) run the program, sending its output as the required page. The query string is a part of the URL which is passed to the program. Its use permits data to be passed from the HTTP client (often a web browser) to the program which generates the web page.


Receptor-Related Impairments

The following types of receptor-related impairments have been described:


Redaction is the process of removing, or sanitizing, personal or confidential content from a document. Print based documents are redacted through the process of covering sensitive text with a black marker. Electronic documents, such as PDFs, can use redaction tools to permanently delete sensitive information, including specific text and illustrations.

Refreshable Braille Display

An electro-mechanical device for displaying Braille characters, usually by means of raising the dots through holes in a flat surface. Refreshable braille displays sit under a regular computer keyboard, and smaller displays (usually 18-40 cells) are available on some models of notetakers.

Rendered Content

Rendered content is the part of content capable of being perceived by a user through a given viewport (whether visual, auditory, or tactile). Some rendered content may lie “outside” of a viewport at some times (e.g., when the user can only view a portion of a large document through a small graphical viewport, when audio content has already been played, etc.). By changing the viewport's position, the user can view the remaining rendered content.

Rendered content can also appear in Dynamic PDF/XFA documents which can show content based on the previous input by an end user.

Rehabilitation Act

See U.S. Section 508

Rehabilitation Act, 1973

A U.S. Congressional act designed to foster economic independence for people with disabilities. Authorized grants to states for vocational and other rehabilitation services.

Rehabilitation Act Amendments, 1993

Amended the Rehabilitation Act of 1973 and 1986 to Workforce Investment Partnership Act of 1998 establish a coordinated system of Federal aid programs for vocational education, adult education, and job training at State and local levels.


For the purposes of accessibility, remediation refers to the techniques of taking an existing PDF document, or Legacy PDF, and employing tagging techniques to make the legacy PDF fully accessible.

Repair Content

The term “repair content” refers to content displayed within a PDF document by an end user which cannot be interpreted properly by the user choice of adaptive technology. “Repair text” means repairing content consisting only of text. This requires a manual review and repair process of content in the document object.

Resource Dictionary

Associates resources with names, uses the objects in content datastreams with the resource objects themselves and organizes them in various categories (e.g. font, color space, pattern).

Retinal Dystrophy

See Retinitis Pigmentosa

Retinitis Pigmentosa (RP)

Belongs to the Receptor-Related Impairments and is a congenital inherited disease, which causes the breakdown of pigment in the retina (both rods and cones degenerate). It usually starts with night-blindness; as the condition worsens, people may also have difficulty seeing in dim light. Eventually, RP may progress to loss of peripheral vision, which leads to tunnel vision. Color vision may also be affected.

Retinal Disease

Retinal diseases may cause sudden visual loss. Because the retina is being affected, there is usually a concomitant relative afferent pupillary defect. Conditions that affect or destroy the retina include retinal detachment; macular disease (e.g., macular degeneration); and retinal vascular occlusions, the most important of which is central retinal artery occlusion.


The retina in our eyes contains two basic types of light sensors (photoreceptors), rods and Cones, which form independent visual systems that are dedicated to special tasks. Rods are primarily used for brightness and motion perception, as well as for night vision.


Actions and activities assigned to or required or expected of a person or group. With respect to accessibility, we have to care for the following three roles:

1. Blind user

  • Cannot use the monitor
  • Cannot use the mouse or similar pointing device
  • Needs screen reader and / or a Braille display
  • Is able to use the keyboard
  • Needs “where am I / what can I do” information
  • Wants textual information instead of graphical information

2. Visually challenged user

  • Can use the monitor
  • May need screen magnifiers or bigger fonts
  • May need specific colour adjustments
  • Wants graphical information, textual only as a fallback
  • Is able to use the keyboard and pointing device
  • Needs “where am I” information (with huge magnification, he looses the overview)

3. Motion impairment

  • Cannot use the mouse or similar pointing device


Scalable Vector Graphics (SVG)

Scalable Vector Graphics (SVG) is a family of specifications of an XML-based file format for describing two-dimensional vector graphics, both static and dynamic (i.e. interactive or animated).

The SVG specification is an open standard that has been under development by the World Wide Web Consortium (W3C) since 1999.

SVG images and their behaviors are defined in XML text files. This means that they can be searched, indexed, scripted and, if required, compressed. Since they are XML files, SVG images can be created and edited with any text editor, but drawing programs are also available that support SVG file formats.

All major modern web browsers, support and render SVG markup directly with the very notable exception of Microsoft Internet Explorer (IE)[3] The Internet Explorer 9 beta supports the basic SVG feature set.[4] Currently, support for browsers running under Android is also limited.

Scanning Software

Scanning software is adaptive software used by individuals with some physical or cognitive disabilities that highlights or announces selection choices (e.g., menu items, links, phrases) one at a time. A user selects a desired item by hitting a switch when the desired item is highlighted or announced.


A usability term which describes the ability of a document to clearly indicate it's purpose and guide the user towards a mutually desired outcome.

Screen Magnifier

A software program that magnifies a portion of the screen, so that it can be more easily viewed. Screen magnifiers are used primarily by individuals with low vision. Most operating systems have a built in screen magnifier, however other third party applications are more popular like Ai Squared's ZoomText, Magnifier and MagReader.

Screen Reader

Software used by individuals who are blind or who have dyslexia that interprets what is displayed on a screen and directs it either to Speech Synthesis for audio output, or to refreshable braille for tactile output. Some screen readers use the document tree (i.e., the parsed document code) as their input. Older screen readers make use of the rendered version of a document, so that document order or structure may be lost (e.g., when tables are used for layout) and their output may be confusing.

Popular screen reader titles include: Freedom Scientific's JAWS, GW Micro's Window-Eyes, Serotek's System Access, Ai Squared's MagReader, Microsoft's Narrator, Apple Inc's VoiceOver, and the Open Source NonVisual Desktop Access (NVDA).

Search Engine Optimization

Search engine optimization describes a part of the process to making certain a website or document appear to its best advantage in search engine results pages. The use of metadata techniques in PDF documents and wesbites can improve the content's search engine results.


Describes a set of procedures applied to data communications to ensure that information is transferred exactly as the sender and receiver intend, and in no other way. Security generally breaks down into Integrity, Authentication, Confidentiality and Privacy. Improper security techniques can render PDF content completely inaccessible to adaptive technology users.


Accelerator keys and function keys are further approaches to providing keyboard access. These keys are used to execute a function connected to an element or put the focus on an element.

Seizure Disorder

Some individuals with seizure disorders are triggered by visual flickering or audio signals at a certain frequency.

Simpler Language Alternative

Is comparable information on the same subject which is written at a more introductory or elementary level.

Source Document

In the context of accessibility, source documents refer to the original authoring application file formats such as Microsoft Office Suite applications (Microsoft Word, Excel, Powerpoint), Adobe InDesign, or Quark's QuarkXPress desktop publishing.

Source Document Accessibility

Source document accessibility utilizes built in tagging and structure capabilities that are included as options within authoring applications. All source document accessibility techniques require additional manual remediation and verification to ensure accurate accessibility.

Speech Synthesis

The process of automatic generation of speech output from data input which may include plain text, formatted text or binary objects.

Speech Synthesizers

Convert electronic text to speech, and can be used with a variety of access hardware and software.


A set of attributes representing the properties of a component at some point in time.

Style Sheets

See Cascading Style Sheets


Tab Chain

Manages the list of element on a page that can have the focus (also known as Accessibility Hierarchy). These active elements are automatically added to the hierarchy by the browser when it parses the source code. By default, elements are added to the hierarchy in the order they appear in the HTML source of the page (source order).


A table is a means of arranging data in rows and columns. The use of tables is pervasive throughout all communication, research and data analysis. Tables appear in print media, handwritten notes, computer software, architectural ornamentation, traffic signs and many other places. The precise conventions and terminology for describing tables varies depending on the context. Further, tables differ significantly in variety, structure, flexibility, notation, representation and use. In books and technical articles, tables are typically presented apart from the main text in numbered and captioned floating blocks.

Without proper structuring of table content within a PDF document, content will be read in a linear fashion which eliminates all navigation and usability for adaptive technology users.

Tab Order

An assistive technology strategy. For people who cannot use a mouse, one strategy for rapidly scanning through links, headers, list items, or other structural items in a PDF or a Web page is to use the tab key to go through the items in sequence. People who are using screen readers -- whether because they are blind or dyslexic -- may tab through items on a page, as well as people using voice recognition.

Tabular Information

When tables are used to represent logical relationships among data -- text, numbers, images, etc., that information is called “tabular information” and the tables are called “data tables”. The relationships expressed by a table may be rendered visually (usually on a two-dimensional grid), aurally (often preceding cells with header information), or in other formats.

Tactile Graphics

Images used by blind people to obtain information that sighted people get from looking at pictures. Students learning geography for example would be lost without maps of regions being studied. A blind student without equivalent tactile maps is at an enormous disadvantage relative to sighted peers.

Tagged PDF

Is a technique employed within a PDF that provides structure and orders information to allow PDF documents to be read and navigated by screen-readers and to be reflowed to fit different display screen sizes. To accomplish this, Tagged PDF marks, or tags, the various elements that make up a page.

Accessibil-IT specializes in PDF accessibility and has developed a new leading approach to tagging PDF content to ensure adaptive technology users can easily access and navigate all content within a PDF or PDF Form.


PDF tags are similar in many ways to XML tags. PDF tags indicate document structure: which text is a heading, which content makes up a section, which text is a bookmark, and so on. A logical structure tree of tags represents the organizational structure of the document. Thus tags can indicate the precise reading order and improve navigation—particularly for longer, more complex documents—without changing the appearance of the PDF.

Tag Tree

Adaptive technologies determine how to present and interpret the content of the document by using the tag tree. Most assistive software depends on document structure tags to determine the appropriate reading order of text and to convey the meaning of images and other content in an alternate format, such as sound. An untagged document does not have structure information, and Acrobat must infer a structure based on the Reading Order preference setting. This situation often results in page items being read in the wrong order or not at all.

Text Aware

A device which is “text-aware” is able to communicate information expressed in text to the user of the device. A web browser extracts text and displays it visually on a screen. A screen reader extracts text and displays it as speech. Text-aware devices are a significant mode of universal communication, since a single input format can be communicated in a variety of different output formats.

Text Browsers

An assistive technology device. Text browsers such as Lynx are an alternative to graphical user interface browsers. They can be used with screen readers for people who are blind. They are also used by many people who have low bandwidth connections and do not want to wait for images to download.

Text Descriptions

See Descriptions

Text Equivalents

Text content that describes information on the screen that's contained in graphic, Flash, or other multimedia files. Text equivalent is often provided using captions, ALT text, or transcripts. The alternate text must convey the same function or purpose for the user with a disability as the non-text content does for others.


The process of automatic generation of speech output from text or annotated text input.

Text Transcript

A text transcript is a text equivalent of audio information (e.g., an audio-only presentation or the audio tracks of a movie or other animation). It provides text for both spoken words and non-spoken sounds such as sound effects. Text transcripts make audio information accessible to people who have hearing disabilities and to people who cannot play the audio. Text transcripts are usually created by hand but may be generated on the fly (e.g., by voice-to-text converters). Refer also to the definitions of captions and collated text transcripts.


A “transcript” is a text representation of sounds in an audio clip or an auditory track of a multimedia presentation. A “collated text transcript” for a video combines (collates) caption text with text descriptions of video information (descriptions of the actions, body language, graphics, and scene changes of the visual track). Collated text transcripts are essential for individuals who are deaf-blind and rely on braille for access to movies and other content.

Tunnel Vision

Belongs to the Receptor-Related Impairments and is like seeing the world through a small tube. This makes it very hard for people to maintain orientation in their daily lives. Two common causes of tunnel vision are Glaucoma and Retinitis Pigmentosa. In the latter case, tunnel vision may be combined with Night-Blindness.


U.S. Section 504

Section of the US Rehabilitation Act of 1973 that protects people in federally-funded programs from discrimination on the basis of a disability.

U.S. Section 508

The term commonly used to refer to the United States federal government's recent enactment of regulations regarding equal access to information technology for people with disabilities. Specifically, Section 508 refers to Section 508 of the United States Federal Rehabilitation Act. In 1998, the United States government amended the Rehabilitation Act to add this section.

Section 508 establishes accessibility requirements for any electronic and information technology that is developed, maintained, procured, or used by the United States federal government. It requires that all U.S. government agencies “ensure that…federal employees with disabilities…have access to and use of information and data that is comparable to the access of those without disabilities.” It also requires that federal agencies developing Web sites ensure that citizens with disabilities have equal access to the information on those Web sites.

To be “Section 508 compliant,” software, Web sites, documentation, and technical support purchased by the federal government after June 25, 2001, must meet the accessibility standards specified in the Section 508 regulations. These standards, as well as definitions of “electronic and information technology,” were issued by the U.S. Access Board (an independent government agency) on December 21, 2000.


International standard assigning a unique value to every meaningful font character or text element. The Universal Character Set [ISO 10646] is practically equivalent to all extents and purposes.

Universal Access

Means, as a general term, that all persons regardless of whether they are poor or rich, have disabilities or not, etc. can access something, be it nature, works of art, technology or, more specifically, information technology.

With respect to information technology, “universal access” means that computer applications, Web pages must be universally accessible. In many countries, this is required by legislation, e.g. in the United States by Section 508.

Universal Design

Designing for the largest audience possible regardless of disability or ability to speak the native language. This is a process rather than an end in itself.


Refers to design features that make a product user friendly. For instance, PDFs or Web sites with usability problems could be hard to navigate, difficult for disabled people to use, or have unclear instructions for use.


An individual or group of individuals acting as a single entity. The user is further qualified as an entity who uses a device to request content and/or resource from a server.

User Agent

User agent is the generic term used to describe any device which might access a web page. User agents include web browsers such as Firefox or Internet Explorer, search engine robots, handheld devices including mobile phones, and accessibility tools such as JAWS.

User Agent Accessibility Guidelines (UAAG)

User Agent Accessibility Guidelines, released by the WAI as guidelines for the implementation of accessible internet browsers.

User Centered Design (UCD)

Is a philosophy as well as a process. It is a philosophy that places the person (as opposed to the 'thing') at the center; it is a process that focuses on cognitive factors (such as perception, memory, learning, problem-solving, etc.) as they come into play during peoples' interactions with things. UCD seeks to answer questions about users and their tasks and goals, then use the findings to drive development and design. UCD can improve the usability and usefulness of everything from “everyday things” (D. Norman) to software to information systems to processes anything with which people interact. As such, User-Centered Design concerns itself with both usefulness and usability.

User Interface

In computer science and human-computer interaction, the user interface (of a computer program) refers to the graphical, textual and auditory information the program presents to the user, and the control sequences (such as keystrokes with the computer keyboard, movements of the computer mouse, and selections with the touchscreen) the user employs to control the program.


Vector Image

One of two major graphic types. (The other type is a bitmap image). Vector graphics are made up of paths — mathematically defined lines and curves with specific start and end points. Line drawings and animations are examples of vector images.


Designates the PDF reference used to generate the document. The processing PDF software must support this version to guarantee correct processing. PDF versions range from 1.0 to 1.8 (as per 2009). PDF 1.4 corresponds to Acrobat 5, PDF 1.8 corresponds to Acrobat 9.

Virtual Reality Modeling Language (VRML)

VRML is a text file format where, e.g., vertices and edges for a 3D polygon can be specified along with the surface color, UV mapped textures, shininess, transparency, and so on. URLs can be associated with graphical components so that a web browser might fetch a webpage or a new VRML file from the Internet when the user clicks on the specific graphical component. Animations, sounds, lighting, and other aspects of the virtual world can interact with the user or may be triggered by external events such as timers. A special Script Node allows the addition of program code (e.g., written in Java or JavaScript (ECMAScript)) to a VRML file.

VRML files are commonly called “worlds” and have the *.wrl extension (for example island.wrl). Although VRML worlds use a text format, they may often be compressed using gzip so that they transfer over the internet more quickly (some gzip compressed files use the *.wrz extension). Many 3D modeling programs can save objects and scenes in VRML format.

Vision Field Loss

Visual information is sent from the eye through the optic nerve to the brain. When the optic nerve or those parts of the brain that are used for seeing are damaged, parts of or even the whole vision is lost. Which part of the vision field is missing, depends on the affected neural pathway(s). The eyes may still work normally.

Vision field loss, a Neural-Related Impairment, can have many causes, such as strokes/CVA (cerebral vascular accident), brain tumors, post surgery implications, or head injury (e.g. caused by car accidents).

Vision Loss

Vision loss or visual loss is the absence of vision where it existed before, which can happen either acutely (i.e. abruptly) or chronically (i.e. over a long period of time).

Various scales have been developed to describe the extent of vision and vision loss based on visual acuity. Early editions of the World Health Organization's ICD described a simple distinction between “legally sighted” and “legally blind”. The ICD-9 released in 1979 introduced the smallest continuous scale which consisted of three tiers: normal vision, low vision, and blindness.

Also see Hypoxia, Media Opacity, Optic Nerve Disease, Retinal Disease, Visual Pathway Disease.

Visual Impairments

Refers to conditions where people are blind, color blind, or have reduced vision capabilities. Often, these people will use assistive technologies like screen readers or magnifiers to help them use computers and navigate through Web sites.

Visual-Only Presentation

A visual-only presentation is content consisting exclusively of one or more visual tracks presented concurrently or in series. A silent movie is an example of a visual-only presentation.

Visual Pathway Disease

Visual pathway disorders are any problems that may impede the visual pathway. Rarely, acute visual loss is caused by homonymous hemianopia and, more rarely, cortical blindness.

Voice Browser

A device that interprets voice markup languages to generate voice output and interpret voice input. Their most common use allows users to access the Internet using a telephone.

Voice Input

Systems that allow a person to access a computer by entering data and issue commands to the computer with spoken words without using a keyboard or mouse.

Voice Output

Spoken words that are conveyed to the user from the computer.


VoiceOver is a screen reader built into Apple Inc.'s Mac OS X and iOS operating systems. By using VoiceOver, the user can access their Macintosh or iOS device based on spoken descriptions and, in the case of the Mac, the keyboard. The feature is designed to increase accessibility for blind and low-vision users, as well as for users with dyslexia. VoiceOver is included on the latest versions of Apple's iPod Shuffle and iPod Nano, as well as recent Macs and iOS devices.

Voice Recognition

A device that allows a user to use his/her voice as an input device. Use it to dictate text into the computer or give commands to open files, save them, etc.



See World Wide Web Consortium


See Web Accessibility Initiative


See Web Content Accessibility Guidelines


See World Wide Web

Web Accessibility

The principle that all web users should have access to information available on the internet.

Web Accessibility Initiative (WAI)

Affiliated with the World Wide Web Consortium. Coordinates with organizations around the world to increase the accessibility of the Web through five primary areas of work: technology, guidelines, tools, education and outreach, and research and development.

Web Browsers (for Non-Visual Output)

Blind and partially sighted people will use one of three possible methods to read pages on the World Wide Web. Users with some sight can use screen magnification software. For users with little or no useful sight the options are Speech Synthesizers or sound card to convert text into speech or a refreshable braille display to convert text into braille.

Web Capture

Designates the process of generating PDF content by importing and possibly converting files from the Internet or local files. The files can be imported in any format such as HTML, GIF, JPEG, text, and PDF.

Without proper format selection, the output PDF can be completely inaccessible for non-visual users.

Web Content Accessibility Guidelines (WCAG)

Guidelines that explain how to make Web content accessible to people with disabilities. The guidelines are intended for all Web content developers (page authors and site designers) and for developers of authoring tools. The primary goal of these guidelines is to promote accessibility. However, following them will also make Web content more available to all users, whatever user agent they are using (e.g., desktop browser, voice browser, mobile phone, automobile-based personal computer, etc.) or constraints they may be operating under (e.g., noisy surroundings, under- or over-illuminated rooms, in a hands-free environment, etc.). Following these guidelines will also help people find information on the Web more quickly. These guidelines do not discourage content developers from using images, video, etc., but rather explain how to make multimedia content more accessible to a wide audience.

The World Wide Web Consortium (W3C) published the Web Content Accessibility Guidelines 1.0 (WCAG 1.0) as a Recommendation in May 1999. The updated for version 2.0 has been published in December 2008 and builds on WCAG 1.0. It has the same aim: to explain how to make Web content accessible to people with disabilities and to define target levels of accessibility. Incorporating feedback on WCAG 1.0, the new version 2.0 focuses on guidelines. It attempts to apply guidelines to a wider range of technologies and to use wording that may be understood by a more varied audience.

Web Page

A “page” of the World Wide Web, usually in HTML format (the file extensions are typically htm or html) and with hypertext links to enable navigation from one page or section to another. Web pages often use associated graphics files to provide illustration, and these too can be clickable links. A Web page is displayed using a Web browser, and can be designed to make use of applets (subprograms than run inside the page) which often provide motion graphics, interaction, and sound.

World Wide Web (WWW)

An Internet service based on the HTTP protocol and HTML pages; provides an easy-to-use user interface for the Internet.

World Wide Web Consortium (W3C)

The World Wide Web Consortium is a non-profit organization founded by Tim Berners-Lee which is responsible for setting the standards for common web creation and access methods. Major documents include the specifications for the HTML and XHTML languages and the Web Content Accessibility Guidelines.



XML Accessibility Guidelines, written by the WAI as guidelines for the implementation of accessible XML based-applications.


XHTML (Extensible HyperText Markup Language) is a combination of XML and HTML which provides developers with a language which uses the HTML specifications within the constraints of the XML format.


XML, or Extensible Markup Language, is a generic format intended for maximum flexibility to provide information in a wide variety of structural formats. A variety of XML specifications exist for different applications, including RSS amongst others.


eXtensible Metadata Platform is an XML grammar for representing document metadata. XMP is a subset of Resource Description Format (RDF).


XSL, or Extensible Stylesheet Language, is a language which describes the formatting and presentation of XML content.




Accessible Web Design - Joseph Dolson Web Accessibility and Development Glossary
Appligent Document Solutions - Glossary of PDF
KDE Accessibility - KDE Glossary of Accessibility Related Expressions
Keynote NetMechanic - Accessibility Dictionary
PDF - PDF Glossary
SAP - Accessibility Glossary
uiAccess - Resources on uiAccess
W3C - WAI Printable Glossary