Glossary

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Height-Field Surface(also: Surface plot, Heightfield plot, 2.5D surface)

A type of 3D data visualisation in which a scalar value (for example, elevation, intensity, pressure, or probability) is plotted over a two-dimensional domain, producing a continuous surface that can be rendered as a mesh, contour map, or draped cloth. Height-field surfaces are…

Heisenberg Effect(also: Heisenberg Problem)

In human-computer interaction, a spatial interaction problem where the act of making a selection disrupts the positional accuracy of the cursor or pointer. In virtual reality freehand gesture contexts, the Heisenberg effect occurs when the physical movement required to confirm a…

Help America Vote Act(also: HAVA)

The Help America Vote Act (HAVA) is a United States federal law enacted in 2002 in response to the voting irregularities of the 2000 Presidential Election. HAVA established mandatory minimum standards for states in key areas of election administration, including requirements…

Help-Seeking(also: Help seeking behavior)

The deliberate process of asking for, searching for, or otherwise obtaining assistance to complete a task, learn a feature, or resolve a breakdown. In accessibility contexts, help-seeking is often shaped by inaccessible documentation, visually oriented tutorials, and the cost of…

Hemi-Attention(also: Hemispatial Neglect, Unilateral Neglect, Visual Neglect)

A neurological condition in which a person has reduced attention or awareness to one side of space, typically the side opposite to a brain injury. Unlike hemianopsia (where visual input is lost), hemi-attention involves a failure to attend to or process stimuli on the affected…

Hemianopsia(also: Hemianopia, Half-Field Vision Loss)

Loss of vision in one half of the visual field in one or both eyes, typically caused by damage to the brain's visual pathways rather than the eyes themselves. The most common form is homonymous hemianopsia, where the same half of the visual field is lost in both eyes — for…

Hemiparesis(also: Hemiplegia, One-Sided Weakness)

Weakness or partial paralysis affecting one side of the body, commonly resulting from stroke, traumatic brain injury, or neurological conditions. Hemiparesis affects motor control, coordination, and strength in the arm, leg, and sometimes face on the affected side. People with…

Hemiplegia(also: Hemiparesis)

A condition involving paralysis or severe weakness on one side of the body, most commonly resulting from stroke but also caused by traumatic brain injury, cerebral palsy, or other neurological conditions. Hemiplegia affects the arm, leg, and sometimes facial muscles on the…

Hemiplegia(also: Hemiparesis)

Paralysis or severe weakness affecting one side of the body, typically caused by stroke, cerebral palsy, or brain injury. Hemiplegia commonly affects the arm, leg, and sometimes face on either the left or right side. For digital accessibility, users with hemiplegia may operate…

Hermeneutical Injustice

Hermeneutical injustice, a concept developed by philosopher Miranda Fricker, is a form of epistemic injustice in which a person's experience is unintelligible to themselves or others because the collective interpretive resources of their community lack the concepts, vocabulary…

Heuristic Evaluation(also: Expert Review, Heuristic Review)

A usability inspection method in which a small group of expert reviewers evaluate a user interface against a set of established design principles or heuristics. Originally developed by Jakob Nielsen, the method is widely used in accessibility assessment where experts review…

Heuristic Evaluation(also: Expert Review, Heuristic Review)

An accessibility or usability evaluation method in which evaluators examine an interface against a set of recognised principles (heuristics) to identify potential problems. In web accessibility, heuristic evaluation typically involves checking pages against WCAG success criteria…

Heuristic Transcoding(also: Rule-based Transcoding)

Heuristic transcoding is the automated transformation of web content to improve accessibility, device compatibility, or readability using a fixed set of predefined rules that inspect the page structure, media types, or visual characteristics — for example, rules that strip small…

Heuristic Walkthrough(also: Heuristic walk-through)

A usability evaluation method proposed by Andrew Sears (1997) that combines scenario-based cognitive walkthrough with heuristic evaluation. Evaluators work through realistic user tasks using a prioritised list of heuristics, surfacing both task-specific and general usability…

Heuristic evaluation(also: Expert review, Usability inspection)

A usability and accessibility evaluation method where trained evaluators systematically assess an interface against a set of recognized principles or guidelines (heuristics) to identify potential problems. In accessibility contexts, heuristic evaluation applies principles from…

Hick-Hyman Law(also: Hick's Law)

A principle from experimental psychology stating that the time it takes a person to make a decision increases logarithmically with the number of available choices. In accessibility and interface design, Hick-Hyman Law informs the practice of limiting the number of options…

Hidden Labour of Disability(also: Invisible Work of Disability, Disability Labour)

The unrecognized time, effort, and energy that disabled people must invest to navigate inaccessible environments, use assistive technologies, manage care relationships, and participate in activities that non-disabled people can do with minimal effort. Examples include spending…

Hidden Markov Model(also: HMM)

A statistical model used extensively in pattern recognition where the system being modeled is assumed to follow a Markov process with hidden (unobserved) states. HMMs have been foundational in both automatic speech recognition and sign language recognition, as they can model…

Hierarchical Task Analysis(also: HTA)

A structured method for describing and analyzing tasks by breaking them down into goals, sub-goals, and operations in a hierarchical tree structure. Originally developed for industrial and safety-critical domains, HTA has been adopted in accessibility research to identify where…

Hierarchy of Impairment(also: Hierarchy of Impairments, Disability Hierarchy)

The hierarchy of impairment refers to the phenomenon where certain types of disabilities and impairments are viewed more favorably or given greater attention than others, both by non-disabled people and within the disability community itself. Research by Mark Deal documented how…

High Contrast Mode(also: High Contrast, High Contrast Display)

An operating system or browser display setting that increases the visual distinction between foreground and background elements by using a limited colour palette with strongly contrasting colours, typically black and white or bright colours on dark backgrounds. High contrast…

High-Functioning Autism(also: HFA, HFASD)

A historically used term describing individuals with autism spectrum disorder who have average or above-average intellectual abilities and can communicate verbally. The term is now considered outdated by many in the autism community and clinical practice, with DSM-5 replacing…

High-Stakes Scenarios(also: Safety-Critical Scenarios)

Situations where errors in AI-generated information could lead to significant safety, health, financial, or social consequences. In the context of visual access technology for BLV users, high-stakes scenarios include medication identification (where misreading a dosage could be…

High-Tech AAC(also: Electronic AAC, Speech-Generating Device)

Augmentative and alternative communication systems that use electronic or digital technology to support communication, including speech-generating devices, tablets with AAC software, smartphones with communication apps, and eye gaze systems. High-tech AAC can offer sophisticated…

Higher Education Accessibility(also: University Accessibility, Postsecondary Accessibility)

The policies, practices, accommodations, and technologies that ensure students with disabilities can participate fully and equitably in college and university programs. Higher education accessibility encompasses physical campus access, digital content accessibility, classroom…

Hijax(also: Progressive enhancement with Ajax)

A web development approach coined by Jeremy Keith that applies progressive enhancement principles to Ajax applications. Hijax starts with a fully functional, accessible HTML page and then layers Ajax functionality on top, so that the site degrades gracefully when JavaScript is…

Histogram of Oriented Gradients(also: HOG)

A feature descriptor technique used in computer vision for object detection that counts occurrences of gradient orientations in localized portions of an image. HOG captures edge and texture information by dividing the image into cells and computing gradient direction histograms.…

Hofstede Cultural Dimensions(also: Hofstede’s Cultural Dimensions, Hofstede Model)

A framework by social psychologist Geert Hofstede characterising national cultures along dimensions such as Power Distance, Uncertainty Avoidance, Individualism versus Collectivism, Masculinity versus Femininity, and Time Orientation. It has been used extensively in…

Holistic Accessibility(also: Holistic Approach to Accessibility)

Holistic accessibility is an approach that considers web accessibility not as an isolated technical concern but as one factor within a broader context including usability, user experience, audience characteristics, usage environment, available technologies, and organizational…

HoloLens(also: Microsoft HoloLens)

A self-contained, wearable mixed reality headset developed by Microsoft that overlays interactive holograms onto the user's real-world environment. HoloLens uses spatial mapping, gaze tracking, gesture recognition (air-tap), voice commands, and a physical clicker for…

Home Accessibility Audit(also: Home Safety Assessment, Indoor Accessibility Assessment, HSSAT)

A systematic evaluation of a residential space to identify barriers to access, safety hazards, and opportunities for modification to support people with disabilities, older adults, or families with young children. Audits typically use standardized checklists — such as the Home…

Home Automation(also: Domotics, Smart Home Automation)

The use of technology to automatically control household systems and appliances such as lighting, heating, ventilation, security, and entertainment. Home automation systems use sensors, timers, and programmable rules to operate devices without manual intervention. For people…

Home Button(also: Home Key, Home Screen Button)

The home button is a persistent, consistently-placed control on a device that returns the user to a known starting state — typically the home screen or main menu — from anywhere in the interface. From an accessibility standpoint, the value of a reliable home button is cognitive:…

Home Page Reader(also: IBM Home Page Reader, HPR)

A talking web browser developed by IBM Japan in the late 1990s, designed specifically for blind and low-vision users. Home Page Reader combined a web rendering engine with the ProTalker text-to-speech synthesiser and exposed navigation commands through the numeric keypad,…

Homebound(also: Housebound)

A status in which an individual has difficulty leaving their home without assistive devices or help from others, typically due to illness, injury, or environmental factors such as lack of transportation. As defined by the U.S. Centers for Medicare & Medicaid Services, homebound…

Homomorphic Encryption(also: Partially Homomorphic Encryption, Fully Homomorphic Encryption, FHE)

Homomorphic encryption is a form of encryption that allows computations to be performed on ciphertext (encrypted data) without first decrypting it, such that the result, when decrypted, matches the result of the same operation on the plaintext. In e-voting, homomorphic tallying…

HoneyPage(also: Honey Page)

A purpose-built test web page used by researchers to study the behaviour of browser extensions, crawlers, or malware in a controlled environment. HoneyPages are instrumented to record network requests, JS API calls, and cookies, and are often designed with known accessibility…

Hong Kong Sign Language(also: HKSL)

Hong Kong Sign Language (HKSL) is the primary sign language used by the deaf and hard of hearing community in Hong Kong. It has its own distinct grammar and linguistic rules that differ significantly from spoken Chinese, Cantonese, and other sign languages such as American Sign…

Hornbostel-Sachs Classification(also: Hornbostel-Sachs System, Sachs-Hornbostel)

A comprehensive system for classifying musical instruments based on how they produce sound, originally developed by Erich von Hornbostel and Curt Sachs in 1914. The system divides instruments into four main categories: idiophones (sound from the vibration of the entire…

Hostile Design(also: Hostile architecture, Deterrent design)

A design orientation in which systems — physical, digital, or bureaucratic — are intentionally configured to deter use, discourage certain populations, or reduce uptake, rather than to enable access. Originally applied to urban features like anti-homeless benches and spikes, the…

House-Brackmann Scale(also: H&B Scale, House-Brackmann Grading System)

The House-Brackmann Scale is a clinical grading system used to assess the degree of facial nerve dysfunction in facial palsy. It ranges from Grade I (normal function) to Grade VI (total paralysis), evaluating voluntary movement of the forehead, eye closure, and mouth. While…

Huffman Coding(also: Huffman Algorithm, Huffman Tree)

A data compression algorithm that assigns shorter codes to more frequently occurring symbols and longer codes to less frequent ones, producing an optimal prefix-free encoding. In accessibility and AAC research, Huffman coding has been applied to the design of scanning interfaces…

Human Activity Recognition(also: HAR, Activity Recognition)

A field of machine learning and ubiquitous computing that uses sensor data — typically from accelerometers, gyroscopes, and other sensors in smartphones, smartwatches, or other wearable devices — to automatically identify and classify physical activities performed by a person.…

Human Augmentation(also: Body Augmentation, Augmentative Technology)

Technologies that extend or enhance human physical or cognitive capabilities beyond their current state, including robotic exoskeletons, prosthetic limbs, sensory substitution devices, and brain-computer interfaces. In disability and accessibility contexts, human augmentation…

Human Computation

A computing paradigm in which humans perform tasks that computers cannot yet do reliably, often embedded within systems that combine human and machine capabilities. The classic example is reCAPTCHA, which used human text recognition to digitise books while verifying users were…

Human Computation(also: Crowdsourced Computing)

A computational approach that harnesses human intelligence to perform tasks that computers cannot easily accomplish alone. In accessibility contexts, human computation powers services like remote sighted assistance for blind users, crowd-powered captioning to improve ASR…

Human Cooperation (Accessibility)(also: Cooperative Shared Control)

In the context of accessible gaming and assistive technology, human cooperation refers to arrangements in which a disabled user (the pilot) and another person (the copilot) jointly operate a single system — for example by splitting game controller inputs between two pads so they…

Human Factors Engineering(also: Ergonomics, Human Factors)

The scientific discipline concerned with designing systems, products, and environments to be compatible with the physical and cognitive capabilities and limitations of the people who use them. In accessibility, human factors engineering applies usability methods and techniques —…

Human Failure Modes and Effects Analysis(also: HFMEA, Human FMEA)

An adaptation of Failure Modes and Effects Analysis (FMEA) that focuses specifically on human performance and error. HFMEA systematically examines each step in a process to identify how humans might fail, why they might fail, and what effects those failures would have. In…

Human Infrastructure

A concept from ICT4D (Information and Communication Technologies for Development) research describing the complex web of people, social relationships, environments, and aspirations that shapes how technology is used in a given context. Developed by Sambasivan and Smyth, human…