Glossary

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Procedural Accessibility

An aspect of web accessibility that addresses the consistency and clarity of interaction sequences and workflows within digital systems. Procedural accessibility ensures that similar services follow the same patterns of interaction — for example, all online purchasing processes…

Procedural Feedback System(also: Process-Oriented Guidance System)

An assistive technology paradigm that provides dynamic, step-by-step support throughout complex multi-step tasks rather than addressing isolated moments of need. Unlike traditional assistive tools that help with discrete actions (e.g., identifying a color or reading a label),…

Progressive Disclosure(also: Staged Disclosure, Layered Interface)

An interaction design pattern that initially presents only the most essential options or information, revealing additional complexity progressively as users need or request it. Progressive disclosure reduces cognitive load and visual clutter by avoiding overwhelming users with…

Prompt engineering(also: Prompt design, Prompt crafting)

The practice of designing and iteratively refining natural language inputs to large language models to elicit more accurate, relevant, or useful responses. In accessibility contexts, prompt engineering is an emerging skill that enables disabled users to customise AI interactions…

Provenance Indicator(also: Source Attribution)

Information that identifies which AI model, trial, or prompt produced a particular piece of content in a multi-model comparison. Provenance indicators help users understand which models generate which claims, enabling them to build mental models of individual model strengths and…

Pull Notification(also: On-Demand Notification, User-Initiated Notification)

A notification or information delivery model where content is provided only when explicitly requested by the user, in contrast to push notifications which are delivered automatically. In assistive navigation contexts, pull notifications allow blind users to request specific…

Put That There(also: Put-That-There)

A pioneering multimodal interactive system built at MIT's Architecture Machine Group (1979-1980), reported by Bolt (1980) and further developed by Schmandt and Hulteen (1982). Users seated in a 'media room' could manipulate a graphical database — such as a Caribbean shipping map…

Ray Casting(also: Raycasting)

An interaction technique in 3-D environments where an invisible ray is projected from a point (such as a user's finger position or controller) into the virtual scene to determine which object the ray intersects first. In VR accessibility, ray casting translates 2-D touch input…

Redundant Input(also: Redundant Input Channels, Multimodal Redundancy)

A design approach in which a user interface accepts the same command through more than one input channel — for example, voice and gesture, keyboard and pointer, or speech and switch — so that users can choose whichever modality suits their current abilities, context, or…

Relevance Threshold(also: Filtering Threshold, Display Threshold)

A user-adjustable cutoff value that determines which content elements are displayed or hidden based on their relevance scores. Elements scoring above the threshold are shown; those below are de-emphasized or removed. Relevance thresholds provide users with agency over how…

Row-Column Scanning(also: RCS, Grid Scanning, Two-Switch Scanning)

The most widely used single-switch selection method for augmentative and alternative communication (AAC) devices and on-screen keyboards. Options are arranged in a two-dimensional grid, and the interface sequentially highlights each row. When the user clicks their switch, the…

Scaffolded interaction(also: Structured interaction, Guided interaction)

A design approach where technology provides structured support that gradually guides users through increasingly complex social or cognitive tasks, with the system mechanics enforcing desired behaviours rather than merely encouraging them. In autism interventions, scaffolded…

Scanning interface(also: Switch scanning, Single-switch access)

An interaction method in which items on a screen are sequentially highlighted one at a time (or in groups), and the user activates a switch to select the currently highlighted item. Scanning interfaces provide computer access for individuals with severe motor impairments who can…

Scene Reading(also: Scene Reader, 3-D Screen Reading)

An interaction paradigm that extends touch-based screen reading concepts from 2-D interfaces to 3-D virtual environments, enabling blind and low vision users to explore virtual scenes nonvisually. Scene reading provides semantic information about virtual objects and their…

Screen Reader Navigation(also: Keyboard Navigation with Screen Reader, Sequential Navigation)

The methods by which blind and visually impaired users move through digital content using a screen reader, primarily via keyboard shortcuts and gestures rather than a mouse or visual scanning. Screen reader navigation is fundamentally one-dimensional and sequential—users…

Scrubbing(also: Video Scrubbing, Timeline Scrubbing)

The interaction of dragging a playhead across a video or audio timeline to preview content at arbitrary positions, typically with real-time visual or audio feedback. Scrubbing is ubiquitous in video editors, NLEs, DAWs, and subtitle-authoring tools. From an accessibility…

Semantic Grounding(also: Meaning Grounding, Form-Meaning Mapping)

A design principle in which practice or interaction is accompanied by explanations that connect the form of an action to its underlying meaning, rather than treating the action as an arbitrary symbol to memorise. In sign language learning, semantic grounding pairs a sign with…

Semantic Navigation(also: Semantic Navigation Framework, Structured Navigation)

An approach to organizing digital content into a meaningful hierarchical structure that users can navigate through logically ordered elements rather than by spatial position. In the context of accessible data visualizations, semantic navigation frameworks arrange chart…

Semantic Redundancy(also: Redundant Multimodal Input)

A design strategy in multimodal interfaces where the same command or message is conveyed simultaneously through multiple input channels, each independently signalling the user's intent. For example, a user might perform a head nod and a hand gesture at the same time, both…

Sensory Substitution(also: Cross-Modal Substitution)

The use of one sensory modality to convey information typically perceived through another. For example, converting visual information into tactile or auditory signals for blind users, or representing sound through vibration for deaf users. Sensory substitution is a fundamental…

Sequential Presentation(also: Step-by-Step Presentation, Progressive Disclosure)

An information delivery method that reveals content incrementally in a structured sequence rather than presenting it all at once. In accessible education, sequential presentation is particularly effective for blind users because tactile perception is inherently sequential —…

Shared Control(also: Collaborative Control, Shared Autonomy)

An assistive technology design approach in which control over a system is dynamically distributed between a user with a disability and an assistant (human or automated), allowing each party to manage the aspects best suited to their abilities. Unlike fully independent or fully…

Shared Movement(also: Linked Locomotion, Guided Movement)

A virtual reality interaction technique that allows one user to move through a virtual environment by attaching to or following another user's avatar, inspired by the physical sighted guide technique used by blind and low vision people. In shared movement, a user can grab a…

Shared Visual Attention(also: Collective Visual Attention, Visual Joint Attention)

A core feature of Deaf-centred interaction in which all participants coordinate their gaze, body orientation, and signing space so everyone can see the current signer, referenced content, and each other. Shared visual attention is foundational to Deaf pedagogy and DeafSpace…

Shared control(also: Collaborative control, Blended control)

A control paradigm in assistive technology where input from multiple sources — such as a wheelchair user and a companion, or a user and an autonomous system — is combined to produce a single action. Shared control enables collaborative interaction that can adapt to the user's…

Signifier(also: Perceived Affordance)

A perceptible cue — visual, auditory, or tactile — that indicates how an element can or should be used, making an underlying affordance discoverable. In Don Norman’s refinement of affordance theory, the affordance is the action possibility, and the signifier is the signal that…

Skeuomorphic Design(also: Skeuomorphism)

A design approach in which digital interface elements are made to resemble their real-world physical counterparts in appearance and behavior. For example, a digital notepad might have lined paper texture and a spiral binding, or a file folder icon might open with a tab-dragging…

Slide Rule

A pioneering touch-based screen reader interaction technique for mobile devices, developed by Kane et al. in 2008, that makes touchscreen content accessible to blind users through finger-driven exploration. Slide Rule allows users to scan items by dragging a finger across the…

Snap Turn(also: Snap Rotation, Comfort Turn)

A virtual reality locomotion technique that rotates the user's viewpoint in discrete angular increments rather than continuous smooth rotation. Typically triggered by a thumbstick or controller input, snap turns rotate the view by a fixed amount (commonly 30-45 degrees) to…

Spatial Scene Reading(also: Direct Touch Scene Reading)

A mode of scene reading interaction where users continuously drag their finger across a touchscreen to freely explore a virtual environment, with objects identified and announced as the finger passes over them. Spatial scene reading preserves the spatial relationship between…

Speed-Accuracy Tradeoff(also: Speed-Accuracy Trade-off, SAT)

A fundamental principle of human motor control where increased movement speed leads to decreased accuracy, and vice versa. Users can choose to move quickly and accept more errors, or move slowly and carefully to minimize mistakes. In accessibility contexts, the speed-accuracy…

Split-Tap Gesture(also: Split Tap)

A two-finger touchscreen gesture where one finger holds position on an object while a second finger taps elsewhere on the screen to activate or select it. Originally developed for the Slide Rule screen reader, the split-tap gesture was adopted by mobile screen readers like…

Steady Tapping

The ability to place a finger on a touchscreen target and hold it still long enough for the system to register a deliberate tap, as opposed to the unintentional movements caused by hand tremor. For users with motor impairments, maintaining a steady tap is a significant challenge…

Stepwise pointing(also: Recursive target acquisition, Tile-based pointing)

A mouse emulation technique in which the screen is divided into a grid of tiles, the user selects a tile to zoom into it, the tile subdivides into smaller subtiles, and this process repeats until the desired screen location is reached at pixel-level precision. Stepwise pointing…

Structural Abstraction(also: Formula Abstraction, Expression Collapsing)

Structural abstraction is an accessibility technique that simplifies complex visual structures — particularly mathematical formulas — by initially collapsing sub-expressions into symbolic summaries and allowing users to progressively expand and explore them at their own pace.…

Structural Navigation(also: Structure-Based Navigation)

A mode of screen reader navigation that allows users to move through content based on its logical or semantic structure rather than reading linearly from beginning to end. In web content, structural navigation involves jumping between headings, landmarks, lists, and other HTML…

Subtle Interaction(also: Discreet interaction)

A design approach in which interactions with a device or digital system are intentionally minimized in visibility, amplitude, or audibility to reduce social disruption, preserve user privacy, and support use in public or semi-public contexts. Subtle interactions include…

Support Indicator(also: Agreement Indicator)

A visual or textual cue that communicates the degree of agreement across multiple AI model responses for a particular claim. Support indicators help BLV users assess claim reliability by showing how many or which models agree. Research has explored four types: source-based ("3…

Supportive Empathy

A therapeutic conversational stance in which a listener responds to another person's feelings with affirmation, validation, and gentle encouragement rather than problem-solving or interpretation. In music-therapy practice supportive empathy is often paired with a 'holding'…

Tactile Exploration(also: Haptic Exploration, Touch-Based Exploration)

The process of perceiving and understanding objects, surfaces, or spatial layouts through systematic touch. For blind and low vision users, tactile exploration is a primary means of gathering spatial and structural information about the physical world. Effective tactile…

Tactile User Interface(also: Tactile UI, TUI)

A user interface designed to be operated and understood through the sense of touch, enabling interaction for blind and low vision users. Tactile user interfaces may include physical buttons with tactile markings, raised icons, textured surfaces that indicate different functional…

Tangible Interface(also: Tangible User Interface, TUI)

A user interface that uses physical objects as representations and controls for digital information, allowing users to interact through touch and manipulation of tangible artifacts. In accessibility contexts, tangible interfaces have been used for braille literacy education…

Tangible Technology(also: Tangible Interface, Tangible User Interface, TUI)

Technology that connects physical objects to digital systems, allowing users to interact with computing through touching, manipulating, and moving real-world objects rather than through screens or keyboards. Tangible technologies are particularly valuable in accessibility…

Tangible User Interface(also: TUI, Physical Interface)

An interface in which users interact with digital information through physical objects and surfaces in the real world. Tangible user interfaces bridge the gap between digital and physical by giving digital data a physical form that can be grasped, moved, and manipulated. For…

Tangible interaction(also: Tangible user interface, TUI, Physical computing)

An interaction paradigm in which users manipulate physical objects and materials to interact with digital information, bridging the gap between the physical and digital worlds. Tangible interfaces leverage people's existing skills in manipulating physical objects, making them…

Tap-to-Hear(also: Point-to-Hear, Tap-to-Listen, Point-and-Click Exploration)

An interaction paradigm used in tactile graphic readers and touch-based accessibility tools where users touch or tap on elements of a tactile graphic to trigger spoken audio descriptions of the element beneath their finger. Tap-to-hear is the current standard approach for…

Tappability(also: Tap Target, Tappable)

The property of a user interface element that indicates whether it can be activated by tapping on a touchscreen device. Tappability is a key concern in mobile accessibility because elements that appear tappable but are not (or vice versa) create barriers for users who rely on…

Target Expansion(also: Expanding Targets, Dynamic Target Sizing)

An interaction technique where clickable interface elements dynamically grow in size as the cursor approaches, making them easier to select while conserving screen space when not being targeted. Research shows target expansion can reduce selection times by up to 14% and error…

Target Size(also: Touch Target Size, Click Target Size, Hit Area)

The physical dimensions of an interactive element on screen — such as a link, button, or checkbox — that a user must point to and activate. Adequate target size is critical for users with motor impairments, tremor, or limited dexterity, as small targets require greater precision…

Target acquisition(also: Target selection, Pointing task)

The process of moving a pointer or input device to a specific on-screen element and selecting it, such as tapping an icon, clicking a button, or choosing a menu item. Target acquisition is a fundamental interaction in graphical user interfaces, and its difficulty is influenced…