Collaborative Web Accessibility Improvement

The Web connects people and brings new opportunities for collaborative activities. This affects not only mainstream Web applications such as wikis and social networking services, but also accessibility-related services. This dissertation describes a collaborative Web accessibility improvement system that can adapt Web content to be more accessible for various types of users. This approach solves accessibility problems in a timely manner through collaboration among Web users who face barriers on a webpage, the site's owners, developers, and volunteers who are interested in Web accessibility. Although concerns about Web accessibility have become widespread among site owners and developers in response to accessibility guidelines and laws, there are still many basic accessibility problems with webpages. The collaborative approach complements the guidelines and legislation and seeks to support accessibility for everyone as a human right. The main theme of this study is to transform the concept of Web accessibility which was thought to be a staff responsibility into a new, broader concept that allows anyone, including the actual users and any volunteers, to refine the accessibility by authoring external metadata. First, this thesis describes a collaborative Web accessibility improvement approach with an implementation called Social Accessibility. This was a 20-month experiment with about 150 visually impaired users and about 340 volunteers. The experiments show the feasibility of and improvements in this approach and I also describe the lessons learned. Thanks to the active participation of the volunteers, improvement requests from the users were handled in times as short as several minutes, with about half of the problems being addressed within 24 hours. The accessibility visualization technology provides an intuitive user interface to help understand and renovate the webpages, and this encouraged the volunteers to join in the work. We improved existing accessibility technologies and proposed a new visualization technique. There is also experimental evidence of the superiority of the new accessibility visualizations. This approach also aims to expand the possible ways of applying external metadata into advanced assistive technologies, allowing for new kinds of user experiences.