# Evaluating Progressive Web App Accessibility for People with Disabilities
## 4 Web Accessibility
### Guidelines and Regulations  
The growing number of national and international laws addressing the accessibility of information and communication technologies (ICT), including the web, has resulted in many different approaches in practice [20]. The first accessibility law adopted by the US in 1990 is the Americans with Disabilities Act (ADA). According to the law, websites and apps are deemed to be places of accommodation and have the duty to be accessible; those that are not accessible are considered to discriminate against people with disabilities [22]. There is a wide range of people with disabilities, including visual, auditory, physical, speech, cognitive, language, learning, and neurological disabilities, and combinations thereof [23]. While numerous guidelines and tools have been developed to help improve access to and understanding of websites' content, the most relevant ones are W3C WCAG, ISO, and Section 508 [24]. Although this paper focuses on W3C WCAG guidelines, it is imperative to mention shortly ISO 9241-151:2008 and Section 508 regulations. With the aim of increasing usability, ISO 9241-151:2008--Guidance on World Wide Web UIs provides guidance on the human-centered design of software web UIs [25]. ISO 9241-151 focuses on the design aspects and provides design guidance and recommendations in four major areas, which are [24, 26]:  
* High-level design decisions and design strategy;
* Content and functionality;
* Navigation, search, and interaction;
* Media design and presentation. In 1998, US Congress amended the Rehabilitation Act of 1973 to require federal agencies to make their electronic and information technology (EIT) accessible to people with disabilities [27]. Section 508 of the Rehabilitation Act applies to the federal agencies, and it requires e-government websites to be accessible to people with disabilities [24]. Section 508 complies with the requirements of other guidelines and standards for both the US and the European Commission, as well as the W3C WCAG. W3C Web Content Accessibility Guidelines (WCAG)  
The World Wide Web Consortium (W3C) has developed Web Content Accessibility Guidelines (WCAG) to make the web accessible to people with disabilities [28]. Following these guidelines will make content more accessible to a wider range of people with disabilities. Making the web accessible benefits individuals, businesses, and society [23], and the WCAG's goal is to provide a single shared standard for web content accessibility that meets the needs of individuals, organizations, and governments internationally [28]. Four different WCAG versions exist: WCAG 1.0, WCAG 2.0, WCAG 2.1, and WCAG 2.2. Each version extends its predecessor and takes its requirements for granted. WCAG 1.0, created by W3C on 5 May 1999, is the foundation stone of WCAG regulations. This first version consists of 14 guidelines or general principles of accessible design. Each guideline has a unique statement, a guideline number, and checkpoints. Respectively, the checkpoints have a unique statement, a checkpoint number, and a link to a section of the Techniques Document where implementations and examples of the checkpoint are discussed. To categorize the checkpoints depending on their importance each checkpoint has a priority level assigned by the Working Group based on the checkpoint's impact on accessibility [29]. In this process, there arose three levels of conformance:  
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* Conformance Level \"A\": all Priority 1 checkpoints are satisfied;
* Conformance Level \"Double-A\": all Priority 1 and 2 checkpoints are satisfied;
* Conformance Level \"Triple-A\": all Priority 1, 2, and 3 checkpoints are satisfied. Although the conformance level was created to identify the priority of each checkpoint, at the same time, as the level increases, it is difficult for web developers to achieve the corresponding requirements, meaning that A-level checkpoints are easier to achieve than the Triple-A. WCAG 2.0 came as an update to WCAG 1.0 in 2008.