Glossary

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User-Generated Content(also: UGC)

Content such as text, images, videos, and reviews created and shared by end users rather than by the website or platform owner. In e-commerce, user-generated content includes customer reviews, review photos, and Q&A sections. This content poses significant accessibility…

User-Generated Content(also: UGC, Prosumer Content)

Web content created and published by non-technical users through platforms like blogs, social media, wikis, and content management systems, rather than by professional web developers. The rise of user-generated content in Web 2.0 has created a significant accessibility…

User-Generated Content Accessibility(also: UGC Accessibility)

The practice of ensuring that user-generated content such as online reviews, forum posts, comments, and social media contributions is accessible to people with disabilities. Unlike curated website content, user-generated content poses unique accessibility challenges because it…

User-Sensitive Inclusive Design(also: USID)

A design methodology that adapts user-centered design principles for contexts where the target user population is highly diverse and where individual differences — including those related to disability — are significant design factors. Unlike Universal Design which aims for…

User-System Model(also: User-System Interaction Model)

A conceptual model that describes the relationship between a user and the technology system they interact with, taking into account the user's abilities, preferences, and needs alongside the system's capabilities, interfaces, and constraints. In accessibility engineering,…

Usher Syndrome(also: Usher's Syndrome)

A genetic condition that is the most common cause of combined deafness and blindness (deafblindness). It is characterized by sensorineural hearing loss present from birth and progressive vision loss from retinitis pigmentosa, which typically begins in adolescence or young…

Utterance-Based System(also: Utterance-Based AAC, Prestored Message System)

A type of augmentative and alternative communication (AAC) system that uses prestored phrases, sentences, or complete utterances rather than requiring users to construct messages word-by-word or letter-by-letter. Utterance-based systems organise prestored text hierarchically,…

VB-MAPP(also: Verbal Behavior Milestones Assessment and Placement Program)

The VB-MAPP (Verbal Behavior Milestones Assessment and Placement Program), developed by Mark Sundberg, is a criterion-referenced assessment and curriculum-planning tool for children with autism and other developmental disabilities. Grounded in Skinner's analysis of verbal…

VBraille(also: V-Braille, Vibration Braille)

A method for representing Braille characters on a smartphone touchscreen using vibration feedback. The screen is divided into a 3-row by 2-column grid matching a standard Braille cell layout, and the phone vibrates when the user touches regions corresponding to raised dots in…

VLAT(also: Visualization Literacy Assessment Test)

A standardized 53-item test developed by Lee, Kim, and Kwon to measure a person's ability to read and interpret data visualizations across 12 chart types. Widely used as a baseline for comparing visualization literacy between groups and for evaluating the impact of assistive…

VPAT(also: Voluntary Product Accessibility Template, Accessibility Conformance Report, ACR)

A standardized document in which vendors report how well their product or service conforms to accessibility standards such as WCAG, Section 508, and EN 301 549. Originally created by the Information Technology Industry Council (ITI), VPATs help procurement teams assess the…

VQA(also: Visual Question Answering)

VQA (Visual Question Answering) is an AI task in which a system answers natural-language questions about the content of an image. In assistive contexts, VQA systems such as Be My AI, Seeing AI, and Aira let blind and low-vision users ask about their visual surroundings - from…

VR Accessibility Training(also: Virtual Reality Training for Accessibility, VR-Based AT Training)

The use of virtual reality environments to teach people with disabilities how to use assistive technologies or navigate unfamiliar real-world scenarios in a safe, controlled setting. VR training allows users to practice spatial and physical skills — such as aiming a smartphone…

VR Controllers(also: Virtual Reality Controllers, Motion Controllers)

Handheld input devices used to interact with virtual reality environments, typically requiring users to grip, hold, and manipulate buttons, triggers, and joysticks. Standard VR controllers present significant accessibility barriers for users with limited hand strength, reduced…

VR Gaming Accessibility

The practice of making virtual reality games playable and enjoyable by people with disabilities. VR gaming presents unique accessibility challenges beyond traditional game accessibility because of its body-centric nature, requiring physical movement, spatial awareness, and…

VR-ASL(also: Virtual Reality American Sign Language)

A simplified adaptation of American Sign Language (ASL) designed for use in virtual reality environments where current controller tracking technology cannot capture the full range of hand and finger movements required for standard ASL. VR-ASL modifies or substitutes signs to…

VRChat

VRChat is a mainstream, user-generated social virtual reality platform where people gather as avatars in user-created 'worlds' that range from quiet scenic environments to busy public social hubs. Users communicate through spatialised voice chat, simple gestures and virtual…

VRML(also: Virtual Reality Modeling Language)

A file format and markup language for describing interactive 3D objects and environments on the web, first standardized in 1995. VRML allowed users to view, rotate, and navigate 3D scenes in web browsers using plugin viewers. In accessibility, VRML was used in early projects to…

Valence(also: Emotional Valence, Hedonic Tone)

In affective science, valence is the dimension of emotional experience that describes positivity versus negativity — whether a feeling is pleasant or unpleasant. Paired with arousal, valence forms the basis of the widely used two-dimensional circumplex model of emotion:…

Valence-Arousal Model(also: VA Model, Circumplex Model, Valence-Arousal Space)

A two-dimensional model of affect, introduced by Russell (1980), that represents emotional states along two orthogonal axes: valence (pleasant versus unpleasant) and arousal (activated versus deactivated). Emotions such as cheerful, tense, calm, and sad map to the four quadrants…

Value Sensitive Design(also: VSD)

A design methodology that accounts for human values in a principled and systematic way throughout the technology design process. Value Sensitive Design integrates three types of investigation: conceptual (identifying stakeholders and their values), empirical (studying how people…

Variable Ability(also: Fluctuating Ability, Dynamic Disability)

The characteristic of many chronic illnesses and disabilities where a person's functional abilities change significantly over time — across days, hours, or even minutes. Variable ability includes both baseline fluctuations (such as flares triggered by environmental factors or…

Variable Font(also: OpenType Variable Font, Parametric Font)

A font file that contains multiple design variations along one or more continuous axes — weight, width, slant, optical size, or custom axes — allowing any intermediate value to be rendered at run time. Defined in the OpenType 1.8 specification (2016), variable fonts reduce file…

Variable Friction(also: Variable Friction Display, Friction Modulation)

A surface haptics technique that dynamically adjusts the friction between a user's fingertip and a touchscreen surface to create the sensation of different textures. Typically achieved through ultrasonic vibration that creates a thin cushion of air beneath the fingertip,…

Variable Pointing Performance(also: Variable Pointing Ability, Intermittent Pointing Difficulty)

A condition where a person's ability to accurately use a pointing device (such as a mouse, trackpad, or touchscreen) fluctuates over time due to factors like physical impairments, fatigue, medication effects, aging, or environmental conditions. Unlike permanent severe motor…

Variation Summary

A concise presentation format for AI-generated image descriptions that explicitly organizes information into three categories: agreements (claims supported by all or most models), disagreements (claims where models conflict), and unique mentions (information provided by only one…

Variation Surfacing(also: Variation Display, Surfacing Variations)

A technique for helping users assess AI reliability by generating multiple responses from one or more AI models and systematically presenting the differences, agreements, and unique mentions across those responses. In the context of image descriptions for blind and low vision…

Variation-Aware Description

A presentation format for AI-generated image descriptions that aggregates multiple model responses into a single coherent, hierarchical description while highlighting variations inline. When multiple AI models describe the same image, a variation-aware description combines their…

Vascular Dementia(also: Multi-Infarct Dementia, Post-Stroke Dementia)

A type of dementia caused by reduced blood flow to the brain, often resulting from stroke or small vessel disease. Vascular dementia is the second most common form of dementia and typically affects processing speed, attention, and executive function rather than memory in its…

Veering(also: Lateral Drift)

The tendency of blind and visually impaired pedestrians to gradually drift away from a straight path while walking, resulting in a curved trajectory rather than a direct line. Veering is a well-documented phenomenon in orientation and mobility research, caused by the absence of…

Verb Inflection(also: Sign Language Verb Inflection, Directional Verbs)

In sign languages, verb inflection refers to the modification of a verb sign's movement path, speed, or direction to encode grammatical information such as subject, object, number, and aspect. Unlike spoken languages where inflection typically involves changes to word endings,…

Verbatim Captioning(also: Verbatim Captions)

A captioning approach that reproduces every spoken word exactly as uttered, including filler words, false starts, and repetitions. Regulators in many countries (e.g., the Canadian CRTC, the US FCC) emphasize verbatim accuracy as a quality requirement. Verbatim captions preserve…

Verbosity(also: Verbosity Level, Screen Reader Verbosity)

Verbosity refers to the level of detail that an assistive technology — particularly a screen reader or voice browser — provides when announcing interface elements and content. Most screen readers allow users to adjust verbosity settings to control how much contextual information…

Verbosity Level(also: Verbosity Setting, Detail Level)

A configurable setting that controls the amount of detail provided in text or audio descriptions of content, particularly for screen reader users and accessible data visualizations. Verbosity levels typically range from low (minimal summary with key points only) to high…

Verbosity Settings(also: Screen Reader Verbosity, Announcement Settings)

Configuration options that control the amount of detail a screen reader or accessible application announces to the user. Verbosity settings allow users to adjust the balance between receiving comprehensive information and reducing auditory noise. In development environments,…

Verifiable Credential(also: VC)

A cryptographically signed statement about a person, organisation, or object that a relying party can verify without contacting the issuer, following the W3C Verifiable Credentials Data Model. Verifiable credentials are the underlying data format used by identity wallets, and…

Verification Mechanism(also: Verification System)

A feature or process that allows users to confirm that a system has correctly understood and executed their intended action. In accessible calendar design, verification mechanisms are critical because BLV users cannot quickly visually scan for errors and rely on the system to…

Verification loop(also: Feedback loop, Edit-verify cycle)

An interaction pattern in which a user performs an action, receives feedback about the result, evaluates whether the outcome matches their intent, and decides whether to accept, undo, or refine the action. In non-visual accessibility contexts, verification loops are essential…

Verified Answer Marker(also: verified solution marker, accepted answer marker)

A visible indicator on a forum or Q&A platform signalling that a particular reply has been confirmed as correct or useful — for example, Stack Overflow's green tick, Apple Discussion Forums' top-ranked reply, or moderator-endorsed 'solution' badges. Verified markers reduce the…

Version segregation(also: Parallel versions, Separate accessible version)

A design practice in which a separate, simplified, or modified version of a product, game, or platform is created specifically for disabled users rather than making the main version accessible. While intended to improve access, version segregation often results in social…

Vibe Coding

A programming style, popularised by Andrej Karpathy in 2025, in which developers express high-level goals to an AI code assistant in natural language and let the AI handle implementation details, iterating conversationally rather than authoring code line-by-line. Vibe coding…

Vibration Feedback(also: Haptic vibration, Vibrotactile feedback)

The use of controlled vibration patterns — varying in duration, interval, intensity, and spatial location — to convey information to a user through the sense of touch. In assistive technology for blind people, vibration feedback has two advantages over audio feedback: it does…

Vibro-Audio(also: Vibrotactile Audio, Vibro-Tactile)

Vibro-audio is a multimodal interaction technique that combines vibration feedback from a device's built-in motor with auditory cues to convey information non-visually. On touchscreen devices, vibro-audio enables users to explore graphical content through touch — the device…

Vibro-Audio Map(also: VAM, Vibro-Audio Display)

A multimodal map representation for touchscreen devices that combines vibrotactile feedback with synchronised audio cues to convey spatial information non-visually. Users explore the map by dragging a finger across the screen; when they cross a feature (a street, a room…

Vibro-audio Interface(also: VAI)

An assistive technology that combines vibration patterns and audio feedback to convey spatial and graphical information through touchscreen devices. Originally developed to make maps and diagrams accessible to people who are blind, VAIs can render shapes, routes, and directional…

Vibromotor(also: Vibration Motor, Vibrotactile Actuator, ERM)

A vibromotor is a small motor that produces vibration, commonly used in haptic feedback devices, smartphones, and wearable technology. The most common types are eccentric rotating mass (ERM) motors, which spin an off-center weight, and linear resonant actuators (LRAs), which…

Vibrotactile(also: Vibrotactile Feedback, Vibrotactile Stimulation)

A form of tactile feedback that uses mechanical vibrations applied to the skin to convey information. Vibrotactile stimulation typically operates at frequencies between 10-500 Hz and is perceived through mechanoreceptors in the skin. In assistive technology, vibrotactile…

Vibrotactile Feedback(also: VTF, Vibration Feedback)

A form of haptic feedback that communicates information through vibration patterns delivered to the skin, typically via small motors embedded in wearable devices such as armbands, gloves, or watches. Vibrotactile feedback offers an alternative sensory channel for conveying…

Vibrotactile Feedback(also: Vibrotactile, Vibrotactile Display, Tactile Vibration)

A form of haptic feedback that uses vibration patterns to convey information through the sense of touch. In accessibility, vibrotactile feedback provides an alternative or complement to visual and auditory output channels, enabling communication with users who are blind, deaf,…

Vibrotactile feedback(also: Tactile vibration, Haptic vibration)

A form of haptic feedback that uses mechanical vibrations applied to the skin to convey information through the sense of touch. Vibrotactile actuators can communicate directional cues, alerts, patterns, and intensity levels without relying on vision or hearing. In accessibility…