## 4 The Proposed Development Model: Holistic Security and Accessibility Layered Architecture (HSALA)
### The Accessibility Enhancement Layer and Accessibility Security Layer  
The last layer which is located above the whole stack is the Accessibility Enhancement Layer, which increases the web application's accessibility for all the users, especially for those with disabilities. The Accessibility Enhancement Layer implements different technologies, such as the following:  
Figure 4: Application layer and application security layer. Figure 5: Content presentation layer and content presentation security layer. WAI-ARIA is a specification published by the World Wide Web Consortium (W3C) which aims to improve the accessibility of web applications. It provides supplementary HTML attributes designed to improve the accessibility of web content and applications for individuals with disabilities. It defines metadata like roles, properties, and states that can describe the behavior of interactive and complex elements, making them perceivable and operable by assistive technologies like screen readers [61]. * Using Semantic HTML elements that describe their purpose improves accessibility. Semantic elements such as headings, navigations, and footers are specifically defined, facilitating the usage of assistance technologies like screen readers, which enhances the navigation flow for the users. * Keyboard Accessibility: It is important to provide keyboard access to all interactive elements (such as links, buttons, and form fields) for those users who cannot use a mouse. This can involve the management of focus order or management of custom controls to make sure that the interactive elements are keyboard navigable. * Alt Text for Images: providing descriptive alternative text (alt attribute) for images, allowing users who cannot see the images to comprehend their content through assistive technology. * Color Contrast and Text Size [62]: Ensuring that there is sufficient color contrast between the text and its background facilitates the reading of the content for people with visual impairments. For instance, in the case of text size relative units (such as _em_ or _rem_), it allows users to increase or decrease the overall font size according to their preferences. * Captions and Transcripts for Multimedia Content: captions in videos and transcripts in audio content eliminate the barriers to access such information for individuals with deafness and hearing loss [63]. The model emphasizes a user-centered design and accessibility testing approach, involving users with disabilities throughout the development process to create truly inclusive applications, such as the following:  
* User personas and scenarios: Developers create detailed personas reflecting users with diverse disabilities--including visual impairments, hearing loss, motor difficulties, and cognitive challenges--and develop scenarios to examine how these individuals engage with the application. These insights guide design decisions that address their specific requirements. * Inclusive design principles:
* Perceptibility: information is presented in multiple formats (e.g., text alternatives for images). * Operability: all functionalities are accessible via keyboard and assistive technologies. * Understandability: consistent navigation and clear instructions help users comprehend and interact with the application. * Robustness: the application is compatible with a wide range of devices and assistive technologies. * Accessibility testing with real users: Testing involves participants with disabilities using assistive technologies like screen readers, magnifiers, and alternative input devices. The feedback from these sessions informs iterative improvements. * Continuous feedback loop: A continuous feedback mechanism ensures that user input directly influences design refinements. This iterative process enhances usability and ensures that the application remains accessible as new features are added.