Glossary

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Novice User(also: Beginner User, First-Time User)

A user who is new to a particular system, task, or interface and has not yet built a mental model of its structure or vocabulary. Novice users typically benefit from menu-driven interfaces, prominent help, progressive disclosure, and forgiving interaction patterns that allow…

Novint Falcon

A consumer-grade 3D haptic input device originally marketed for gaming that has been widely adopted in accessibility research for providing force feedback to people with visual impairments. The device features a grip attached to three arms that can exert forces in three…

Nudge(also: Nudging)

A small change in the presentation, default, or framing of a choice that systematically influences decisions without removing options or significantly altering incentives. Introduced to behavioural economics by Thaler and Sunstein (2008) and grounded in Tversky and Kahneman's…

Number Sense(also: Numeracy Intuition, Numerical Cognition)

The intuitive understanding of numbers, their magnitude, relationships, and how they are affected by operations. Number sense includes the ability to estimate quantities, understand relative size, recognize patterns, and make meaningful comparisons between numbers without…

Numeracy(also: Mathematical Literacy, Quantitative Literacy)

The ability to understand, use, and reason with numbers and mathematical concepts in everyday contexts. Numeracy skills include counting, arithmetic operations, understanding percentages and proportions, interpreting number lines, and making sense of numerical information in…

Nystagmus(also: Involuntary eye movement, Dancing eyes)

A condition characterized by involuntary, repetitive, rhythmic movements of the eyes, which may move side to side (horizontal), up and down (vertical), or in a circular pattern (rotary). Nystagmus can be congenital (present from birth) or acquired later in life due to…

Nystagmus(also: Involuntary Eye Movement, Dancing Eyes)

A condition involving involuntary, repetitive, and rhythmic movements of the eyes, which can be horizontal, vertical, or rotary. Nystagmus can be congenital (present from birth) or acquired later in life due to neurological conditions, medications, or other causes. It often…

OCAP Principles(also: OCAP, Ownership, Control, Access, and Possession)

A set of principles developed by the First Nations Information Governance Centre establishing that First Nations communities must own, control, access, and possess data and information about themselves — their people, territories, resources, and cultural knowledge. OCAP emerged…

OCD Accommodation(also: Family Accommodation)

A behavior — typically by family, friends, or clinicians — that participates in or enables a person with Obsessive-Compulsive Disorder (OCD) to complete a compulsion, for example by providing reassurance, hearing a confession, or making a decision on their behalf. Although…

OCD Cycle

A four-step clinical model describing how Obsessive-Compulsive Disorder is maintained: an obsession (intrusive thought, urge, or image) triggers a feeling of distress, which the person attempts to relieve through a compulsion (a behavior or mental act), producing temporary…

OCR(also: Optical Character Recognition)

Technology that converts images of text into machine-readable text. In accessibility contexts, OCR is used by visual assistance technologies and screen readers to read printed text from photos, signs, documents, and product packaging. While valuable for blind users, OCR has…

OCR (Optical Character Recognition)(also: OCR, Optical Character Recognition, Text Recognition)

A computer-vision technology that converts images of printed, handwritten, or on-screen text into machine-readable character data. OCR is foundational to a wide range of accessibility tools: extracting alt-text for image-based PDFs, reading labels for screen-reader users (e.g.,…

OLAP(also: On-line Analytical Processing, Online Analytical Processing, Data Cube)

OLAP (on-line analytical processing) is a class of database technology that organises data into multi-dimensional 'cubes' — for example, sensor-firing counts indexed by room, time zone, day of week, and week number — and provides fast interactive slice, dice, drill-down, and…

OM Principle(also: Object Model Principle)

A design principle for accessible digital content stating that any digital object is made more accessible by using the application's designated object model for that content rather than visual workarounds. For example, graph titles should be entered in the graphing application's…

OOXML(also: Open Office XML, Office Open XML, ECMA-376)

An XML-based file format standard for representing documents, spreadsheets, presentations, and charts in Microsoft Office applications (Word, Excel, PowerPoint). Introduced in Office 2007, OOXML files use extensions like .docx, .xlsx, and .pptx. For accessibility, the XML…

OPTIMAL-EM(also: Optimised Evaluation Methodology)

A web accessibility evaluation methodology proposed by Hambley, Yesilada, Vigo, and Harper to complement the W3C's WCAG-EM by providing a statistically grounded, complexity-driven method for selecting representative pages from a large website. OPTIMAL-EM comprises six metrics —…

ORBIT Dataset(also: Object Recognition for Blind Image Training)

A disability-first machine learning dataset for teachable object recognition, contributed by people who are blind or have low vision. The original ORBIT dataset (Massiceti et al., 2021) contains 3,822 videos of 486 objects from 67 data collectors, predominantly in the UK and…

OSARA(also: Open Source Accessibility for the REAPER Application)

An open-source extension for the REAPER digital audio workstation that significantly improves its accessibility for screen reader users. OSARA adds enhanced spoken feedback for track and item properties, transport state, mixer controls, and other DAW elements that would…

OWL(also: Web Ontology Language, OWL 2)

The Web Ontology Language (OWL) is a W3C standard for defining and instantiating formal ontologies on the web, enabling machines to interpret the meaning and relationships of information rather than just displaying it. OWL supports accessibility by contributing to the Semantic…

Obfuscation(also: Content Obfuscation, Visual Obfuscation)

AI-enabled techniques that automatically detect and remove or conceal private content in images and videos by applying filters such as blurring, masking, or blocking. In the context of visual assistance technologies, obfuscation aims to protect blind users from inadvertently…

Object Detection(also: Object Recognition)

A computer vision technique that identifies and locates specific objects within images or video frames, typically by drawing bounding boxes around detected items and classifying them. In video accessibility, object detection enables automatic identification of video elements…

Object Hierarchy(also: Object Group, Hierarchical Object Organization)

A structured organization of objects into parent-child relationships that allows users to navigate from high-level categories to increasingly specific details. In accessible virtual environments, object hierarchies enable BLV users to progressively explore complex scenes by…

Object Localisation(also: Object Localization, Spatial Localisation)

The process of determining the position and location of an object within a physical or virtual space. In accessibility, object localisation is a key challenge for blind and visually impaired users interacting with spatial interfaces, virtual environments, or graphical content.…

Object Permanence

The cognitive understanding that objects continue to exist even when they cannot be directly perceived through sight, sound, or touch. This developmental milestone, typically achieved in infancy for sighted children, can develop differently in blind children who lack visual…

Object Recognition(also: Object Detection)

A computer vision capability that identifies and classifies objects within images or video frames. In visual assistance technologies, object recognition enables automated description of what the camera captures, helping blind users identify items in their environment. However,…

Object Status Recognition(also: Object State Recognition, Object Transformation Detection)

The computer vision task of identifying the current condition or transformation state of objects, such as whether an ingredient is raw, chopped, sauteed, or blended. Object status recognition goes beyond simple object detection (identifying what is present) to understand how…

Object recognition(also: Object detection, Image classification)

A computer vision task in which a system identifies and labels objects within images or video, often using deep learning models trained on large datasets. For blind and low-vision users, object recognition is a core capability of camera-based assistive technologies like Seeing…

Object-Based Audio(also: OBA, Object-Based Broadcasting)

An audio production and delivery paradigm in which speech, music, effects, and ambience are transmitted as discrete objects with metadata describing their role and relationships, rather than as a single mixed stream. The receiver renders the final mix, enabling per-listener…

Object-Based Cropping(also: Semantic Cropping, Object-Aware Cropping)

An image cropping approach that allows users to select which objects to keep in an image rather than specifying pixel coordinates or spatial boundaries. Object-based cropping uses computer vision to identify and segment objects (e.g., "the dog", "the chair"), then crops the…

Object-oriented analysis and design(also: OOA, OOD, OOAD)

A software engineering methodology that describes complex systems in terms of related, cooperating entities (objects) rather than as sequences of procedures. For example, a user interface can be modelled as relationships between content objects, presentation objects, and…

Observational Study(also: Field Observation, Naturalistic Observation)

A research method in which investigators systematically watch and record behaviors, interactions, and practices in a natural setting without manipulating variables or conditions. In accessibility research, observational studies are used to understand how people with disabilities…

Obsession(also: Obsessive Thought, Intrusive Thought)

Recurrent, persistent, unwanted thoughts, urges, or mental images that cause significant anxiety or distress. In OCD, obsessions are experienced as intrusive and involuntary, and the person recognizes them as products of their own mind rather than external influences. Common…

Obsessive-Compulsive Disorder(also: OCD)

A mental health condition affecting approximately 2% of the world population, characterized by recurrent, intrusive, unwanted thoughts (obsessions) that cause significant anxiety, and repetitive behaviors or mental acts (compulsions) performed to relieve that anxiety. OCD…

Obstacle Avoidance(also: Obstacle Detection)

The ability to detect and navigate around physical barriers in one's path, a critical mobility skill for blind and visually impaired people. Traditional obstacle avoidance relies on long cane techniques (sweeping the cane side to side to detect ground-level hazards) and guide…

Obstacle Detection(also: Obstacle Avoidance)

Technology or techniques that identify physical barriers in a person's path and alert them in time to take corrective action. For people who are blind or visually impaired, obstacle detection systems use sensors (ultrasonic, infrared, LiDAR, or camera-based) embedded in devices…

Occlusion(also: Hand Occlusion, Finger Occlusion, Visual Occlusion)

In the context of touchscreen and pen-based interaction, occlusion refers to the user's hand or finger blocking their view of content on the screen while interacting with it. Occlusion is a significant accessibility barrier, particularly for older adults and users with motor…

Occupancy Grid(also: Occupancy Map, Mental Occupancy Grid)

A spatial representation that divides an environment into a grid of cells, each indicating whether that location is occupied by an object, free space, or unknown. In accessibility and assistive technology, occupancy grids are used to help people with visual impairments build…

Occupancy Grid Map(also: 2D occupancy grid, Grid map)

A representation of an environment as a grid of cells, where each cell is labelled as walkable (free space), non-walkable (obstacle or wall), or unknown. Occupancy grid maps are a standard data structure in robotics and are increasingly used in blind-navigation systems built on…

Occupational Therapist(also: OT, Occupational Therapy)

An occupational therapist is a licensed healthcare professional who helps people participate in the 'occupations' of daily life — self-care, work, school, leisure, and community roles — through therapeutic activity, environmental modification, and assistive technology. In…

Occupational Therapy Assessment(also: OT Assessment, OT Evaluation, Client Evaluation)

Occupational therapy assessment is the systematic process by which an occupational therapist evaluates a client's physical capabilities, cognitive function, emotional state, and ability to perform daily living activities in order to develop an appropriate treatment plan.…

Occupational therapy(also: OT)

A healthcare profession focused on enabling people to participate in meaningful daily activities ("occupations") despite physical, cognitive, sensory, or psychosocial challenges. Occupational therapists assess individuals' functional abilities, recommend assistive technology,…

Occupational therapy(also: OT)

A healthcare profession focused on enabling people to participate in meaningful daily activities (occupations) by addressing physical, cognitive, sensory, and environmental barriers. Occupational therapists assess individual abilities, recommend and customize assistive…

Ocular Aberration(also: Optical Aberration, Wavefront Aberration)

Ocular aberration refers to deviations in the way light is focused by the optical components of the eye (cornea and lens) compared to an ideal optical system. These aberrations distort the image formed on the retina and contribute to blurred or distorted vision. Lower-order…

Ocular normativity(also: Ocularcentrism, Ocular norm, Visual normativity)

A concept from critical disability studies describing the cultural assumption that sight is the primary, most reliable, and most natural mode of knowing and perceiving the world. Ocular normativity positions visual interaction as the default and universal way to engage with…

Ocularcentrism(also: Visual Bias, Vision-Centrism)

The privileging of visual perception and visual ways of knowing in the design of technologies, interfaces, and information systems. Ocularcentrism in technology design manifests when visual assumptions are embedded in systems that are intended to be accessible — for example,…

Off-Device Processing(also: Cloud Processing, Remote Processing)

Computing performed on external servers rather than on the user's local device, requiring data to be transmitted over the internet. In the context of visual assistance technologies, off-device processing raises privacy and security concerns because users' images and videos —…

Off-Screen Model(also: OSM, Virtual Buffer)

A data structure maintained by screen readers that represents the content and structure of the visual display in a form that can be navigated non-visually. Traditional screen readers intercept system calls to build this off-screen model because they did not have direct access to…

Off-the-Shelf Technology(also: OTS, Commercial Off-the-Shelf, COTS)

Commercially available products designed for the general consumer market without customization for specific user groups. In accessibility research, off-the-shelf technology refers to mainstream devices like smart speakers, thermostats, and lighting systems that were not designed…

Offline Access(also: Offline Mode, Disconnected Access, Offline-First)

The ability to use digital content, applications, or services without an active internet connection. Offline access is an important accessibility consideration because it ensures that users in areas with unreliable, expensive, or nonexistent connectivity — including many rural…

Older Adults(also: Seniors, Elderly, Aging Population)

People typically aged 65 and above who may experience age-related changes in vision, hearing, motor control, and cognition that affect how they interact with technology. Designing for older adults requires attention to larger text sizes, higher contrast, simplified navigation,…