Glossary

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LLM-as-Judge(also: LLM as a Judge, Model-as-Judge)

An evaluation methodology in which a large language model is prompted to assess the quality of some artifact — generated text, code, a UI, or a response from another model — according to a structured rubric. LLM-as-judge is attractive because it scales automated evaluation to…

Manual Accessibility Testing(also: Manual Testing, Manual Evaluation, Human Testing)

The process of evaluating web content accessibility through direct human inspection rather than automated tools. Manual testing is essential because many WCAG success criteria cannot be fully evaluated by automated means — they require human judgment about whether content is…

Metamessage(also: Designer's Metamessage)

In Semiotic Engineering theory, the overarching one-way message that a designer sends to users through the system's interface, communicating who the system is for, what it can do, how to use it, and why it was designed that way. The metamessage is encoded through interface signs…

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 —…

PDF Form(also: PDF Fillable Form, Interactive PDF Form, AcroForm)

A PDF document that contains interactive form fields — text boxes, checkboxes, radio buttons, signatures, dropdowns — that users can fill in and submit electronically, rather than a static PDF meant only for reading. PDF forms are widely used for government applications,…

Pa11y

An open-source automated accessibility testing tool that runs from the command line and in continuous-integration pipelines. Pa11y can drive either axe-core or HTML CodeSniffer as its underlying rule engine, returning JSON-formatted results classified by severity (critical,…

Perceived Accessibility(also: Subjective Accessibility, Accessibility-in-Use)

Perceived accessibility refers to the subjective quality by which users experience the accessibility of a website or application, as opposed to its objective compliance with accessibility standards. Research has shown that guideline-conformant websites can still be perceived as…

Personalized Accessibility(also: Personalized Web Accessibility, User-Tailored Accessibility)

An approach to accessibility evaluation and design that considers the specific disability profile, capabilities, and needs of individual users rather than treating accessibility as a single universal property. Personalized accessibility evaluation tools filter WCAG success…

Probabilistic Sampling(also: Random Sampling, Statistical Sampling)

A sampling method in which every member of a population has a known, non-zero probability of being selected for the sample. In accessibility evaluation, probabilistic sampling of web pages allows auditors to make statistically valid generalisations about the overall…

Proxy Feedback(also: Proxy User Testing, Surrogate Feedback)

A user research method in which feedback on designs or prototypes is gathered from people who are close to the target users — such as carers, therapists, family members, or support workers — rather than from the users themselves. This approach is used when direct communication…

RAVEN(also: Rule-based Accessibility Validation Environment)

An accessibility testing tool developed by IBM as a set of Eclipse IDE plug-ins for verifying the accessibility of graphical user interface applications. RAVEN uses aspect-oriented programming techniques to provide non-invasive, automatic to semi-automatic accessibility…

Representative Sampling(also: Representative Page Sampling)

In web accessibility auditing, the practice of selecting a subset of pages from a website that statistically reflects the full site, so that evaluation findings can be generalised to pages not directly audited. WCAG-EM requires that a 'representative sample' be included…

SERPA(also: Streamlined Evaluation and Reporting Process for Accessibility)

A programmer-centric methodology for conducting and reporting website accessibility evaluations, proposed by Law, Jacko, and Edwards in 2005. SERPA restructures the traditional accessibility evaluation process around the needs and constraints of the developers who must implement…

Scenario-Based Evaluation(also: Path-Based Testing, User Journey Testing)

An accessibility evaluation approach that assesses the complete user experience across a sequence of steps needed to accomplish a task, rather than testing individual pages in isolation. For example, evaluating an e-commerce checkout means testing every step from product search…

Screen Reader Proxy

An interface that sits between an automated agent or testing tool and an application, translating programmatic inputs (swipe, double-tap, type) into genuine screen reader gestures and capturing the resulting announcements as structured transcripts. Unlike driving an app via its…

Semi-Automatic Evaluation(also: Semi-Automated Testing, Guided Manual Evaluation)

An approach to accessibility evaluation that combines automated checks with human expert judgment. Semi-automatic tools run algorithmic tests to detect issues that can be identified programmatically — such as missing alt text or invalid ARIA attributes — and then guide the…

Semiotic Inspection Method(also: SIM, MIS)

An evaluation method from Semiotic Engineering theory that systematically assesses the communicability of an interactive system by examining how well the designer's intended message is conveyed through the interface. The evaluator analyzes three types of interface signs…

Sensitivity(also: Recall, Thoroughness, Completeness)

In the context of accessibility evaluation, sensitivity (also called recall or thoroughness) is the proportion of true accessibility problems that are successfully identified and reported by an evaluator. High sensitivity means that most real barriers are found, while low…

Structured Walkthrough(also: Guided Walkthrough, Accessibility Walkthrough)

An accessibility evaluation method in which an evaluator is guided through a systematic series of checks using predefined steps, instructions, and heuristics. Unlike a full WCAG conformance review which requires expert knowledge to interpret success criteria, a structured…

Testability(also: Reliably Human Testable, Machine Testable)

In the context of accessibility standards, testability refers to the degree to which a guideline or success criterion can be evaluated with consistent, reproducible results — either through automated tools (machine testable) or through human inspection where at least 80% of…

UWEM(also: Unified Web Evaluation Methodology)

The Unified Web Evaluation Methodology (UWEM) is a standardized European methodology for evaluating web accessibility conformance with WCAG. Developed through EU-funded projects including the European Internet Accessibility Observatory (EIAO) and Support-EAM, UWEM provides…

Unified Web Evaluation Methodology(also: UWEM)

A standardized methodology developed by the European Web Accessibility Benchmarking Cluster (WAB Cluster) for evaluating the accessibility of websites in a consistent, comparable way. UWEM provides formulas for calculating quantitative accessibility scores from WCAG checkpoint…

Virtual Auditing(also: Remote Auditing, Virtual Accessibility Audit)

Virtual auditing is a method of assessing the accessibility of physical environments by remotely examining street-level imagery, such as Google Street View, rather than conducting in-person inspections. Research has shown that tool-mediated virtual audits of urban infrastructure…

Vote Verification(also: Cast-as-Intended Verification, Recorded-as-Cast Verification)

The ability for a voter to confirm that their vote was correctly cast, recorded, and counted — a core requirement for trustworthy electronic and online elections. Traditional code-based verification schemes (Helios, Belenios) ask the voter to compare random strings between their…

Web Accessibility Barrier(also: WAB, Accessibility Barrier)

Any element, design pattern, or technical implementation on a web page that prevents or hinders people with disabilities from accessing, understanding, or interacting with content. Common web accessibility barriers include images without alternative text, videos without…

Web Accessibility Barrier Score(also: WAB, WAB Score)

A quantitative metric for measuring the accessibility level of a website, defined as the mean value of the failure rate of accessibility checkpoints on a page, weighted by the priority of each checkpoint. The failure rate is the number of violations of a checkpoint divided by…

Web Accessibility Quantitative Metric(also: WAQM)

An accessibility evaluation metric that calculates a quantitative score for a website based on automatically generated evaluation reports. WAQM computes the failure rate for each tested page, then derives the overall website accessibility value by weighting pages according to…

Web Complexity(also: Page Complexity, Website Complexity)

A measure of the technical sophistication and structural density of a web page, typically assessed by the number and types of HTML elements, scripts, embedded objects, and interactive features present. In accessibility research, web complexity is an important factor because more…

Web Crawling(also: Web Spidering, Web Scraping)

The automated process of systematically browsing and indexing web pages by following hyperlinks from a starting URL. In accessibility evaluation, web crawlers are used to discover and catalogue pages across a website for audit purposes. Two primary traversal strategies exist:…

axe DevTools(also: axe, axe-core)

A widely used suite of automated accessibility testing tools developed by Deque Systems, available as browser extensions, command-line tools, and integrable libraries. The axe-core engine is an open-source JavaScript library that tests web content against WCAG success criteria…

mobileOK(also: mobileOK Basic Tests, W3C mobileOK)

A set of machine-automatable tests published by the W3C to verify conformance with Mobile Web Best Practices 1.0. The mobileOK Basic Tests define a subset of best practices that can be unambiguously evaluated by automated tools, checking for issues such as unsupported image…