A Framework for Building Accessible Websites for Visually Impaired

Transcription

1 A Framework for Building Accessible Websites for Visually Impaired Helani Wanniarachchi 1, D. K. Withanage 2 1 Faculty of Information Technology, University of Moratuwa, Sri Lanka 2 Faculty of Information Technology, University of Moratuwa, Sri Lanka Abstract Proper access to World Wide Web has emerged as an essential need for all kinds of groups in society. There is no apparent alternative to it in most disciplines where it is highly involved. Therefore it is crucial to make the World Wide Web a place for all human beings regardless of their capabilities, social status, wealth & power, etc. One potential group that is discriminated in terms of web accessibility is visually impaired users because of the strong tendency of web sites and applications are towards visual consumption. In recent years this issue has been given due consideration by various authorities and they are in the process of generating a significant pressure on web content providers for making the web friendlier to visually impaired people. At present the laws are also being imposed to strengthen visually impaired people to prompt legal action against organizations that ignore them. But it also brings a great social value to a business if it can provide support in various ways for differently abled people. The challenge in making web content more accessible for visually impaired has been addressed in different ways. Major software platform providers have included lot of supportive features such as voice capabilities in their products. Web development agencies also have started paying attention on accessibility during the development process. This paper includes a study on different types of visual impairments and recommended means of addressing them. It also sheds light on guidelines for developing web sites and applications that are friendly to visually impaired. Output of the research also includes a framework and a convenient tool that can be immensely useful during implementation of accessible web sites and applications. Keywords Assistive technology, Authoring tools, Framework, Visual impairment, Web accessibility I. INTRODUCTION Accessibility to relevant and timely information for both business and day-to-day life has become vital in an unprecedented scale. At the same time, Internet has established itself as world s largest and most pervasive source of information. Therefore it is of paramount importance that a society pays attention for making Internet accessible for everyone. This highlights the requirement for assuring that various unprivileged groups are able to utilize Internet for fulfilling their information needs. Differently abled people constitute one such group. 486 In fact, the United Nations (UN) Convention on the Rights of Persons with Disabilities (2006) recognizes Web accessibility as a basic human right [1]. This research focuses on contributing towards making the World Wide Web accessible for people with visual impairments in particular. Since the Web is primarily meant for visual consumption, currently most web sites have accessibility limitations for millions of visually impaired users. Our research contributes to alleviating this problem in many facets. It sheds light on the scale of impact in making the web accessible for visually impaired and manifests reasons for organizations to invest in it. The study also includes a diligent search into available standards and guidelines that provide ground rules for building a practical developer guide towards better accessibility. In addition, the need for automation infrastructure to bring the developer guide to action in industrial environments is identified. As a first step towards formulating such infrastructure, we design and develop a convenience tool with capabilities to scan web application source code and identify potential improvements in accessibility. II. NEED FOR ACCESSIBILITY The need for Web accessibility can be mainly categorized under social factors, business factors and legal factors. Web accessibility directly addresses the social responsibility to provide equal opportunity for people with disabilities. Indirectly it benefits people without disabilities, including elder people and people with low literacy. In business perspective, the organizations with accessible Websites benefit from search engine optimization (SEO), exposition of corporate social responsibility (CSR), reduced legal risk and increased customer loyalty. For these reasons the costs of implementing Web accessibility pays back with substantial return on investment (ROI) at the end. Various laws, policies and regulations enforced by governments and other standard setting organizations (SSO) have formulated the legal requirements for enabling Web accessibility.

2 III. VISUAL IMPAIRMENTS The phrase visual impairment refers to people with irretrievable sight loss [2]. According to the latest statistics of World Health Organization [3], 285 million people are visually impaired worldwide and 90% of them live in developing countries. All visual impairments fall into two main categories, total blindness and low vision. Statistically 39 million people (14%) are totally blind and 246 million people (86%) have low vision. About 65% of all people who are visually impaired are aged 50 and older. With an increasing elderly population, more people will be at risk of age-related visual impairment. 1.4 million children are irreversibly blind for the rest of their lives. This indicates that their vision cannot be healed by any means of existing medical treatments. We mainly discuss three types of visual impairments specifically total blindness, low vision and colour blindness. A. Total blindness People who fall into NPL (No Perception of Light) category are considered as totally blind. That refers to those people who have entirely lost their sight [4]. This kind of users is able to hear only an audio output. B. Low vision - Low vision user is defined as a person who is having visual acuity not exceeding 6/60 or 20/200 (Snellen chart) [4]. That refers to users who have weak visual acuity to light perception or deficient visual field, but potentially able to use vision for the planning and execution of a task. The users with low vision can observe graphical user interfaces using screen magnifying and colour contrast techniques. They require audio output as well. C. Colour blindness Photosensitive cells in the eye called cones allow us to perceive colour. Cones contain three types of photosensitive pigments that are able to detect red, green, and blue. Those with colour blindness have a deficiency or absence in one or more of these pigments [5]. For this category, it is required to change colour properties accordingly in order to avoid losing any information conveyed in colours. A. WCAG IV. STANDARDS THAT PROVIDE GUIDELINES WCAG (Web Content Accessibility Guidelines) are part of a series of web accessibility guidelines published by the W3C's Web Accessibility Initiative (WAI) [6]. 487 Reasons for adapting WCAG: WCAG is widely accepted as the definitive guidelines on how to create accessible web sites. Guidelines keep up to date. Most user agents and assistive technologies conform to WCAG recommendations. Provide guidelines in a more generic and technology neutral manner. Guidelines are well structured and classified properly. B. WAI-ARIA The advanced user interface controls and dynamic contents in today s Rich Internet Applications are not accessible to visually impaired users. The World Wide Web Consortium published Web Accessibility Initiative - Accessible Rich Internet Applications (WAI-ARIA) specification as a solution to overcome those limitations and it has become a standard recommendation since 2011 [7]. WAI-ARIA is a technical specification that provides a framework to improve the accessibility and interoperability of web content and applications. It provides a means of describing roles, states, and properties for custom widgets and a mechanism to ensure that users of assistive technologies are aware of updates in the application. V. REQUIREMENT FOR A TOOL Web Accessibility is one of the key challenges facing the Internet. Essentially there are few components associated with web accessibility such as the web content, user agents, assistive technologies (AT), web authoring tools and evaluation tools [8]. Fig: 5.1. Components of web accessibility Web content refers to all the information in a web page including basic information such as text, images, sounds and code or mark-up that defines structure, presentation, etc. User agents are the web browsers and the media players that render the web content.

3 Assistive technologies especially for visually impaired users are screen readers, screen magnifiers and voice recognition tools. Our focus is centered on authoring and evaluation tools that refer to the software that creates web sites and evaluate their accessibility. Much of the focus on web accessibility has been on the responsibilities of web developers. Accessible web development involves designing, developing and editing web sites to enable equal access to all users. It requires expertise on the domain and the undertaking is time consuming. Many web developers may lack in experience to apply the available accessibility guidelines in their web sites without special assistance [9]. Therefore the web authoring tools and evaluation tools should play a significant role in assisting web developers to achieve accessibility. VI. RULE SELECTION CRITERIA First, output expected from the research is a collection of practically guiding rules targeted on better accessibility. The accessibility rules we consider are selected in such a manner that they cover all the essential user requirements. The rules are prioritized based on the value added by performing the suggested repair. A. High priority Rules that must be satisfied. The high priority rules are essential to ensure the accessibility. Unless satisfying them the content is inaccessible. B. Medium priority Rules that should be satisfied. These rules will enhance the usability with original content. Unless satisfying them the content can be accessible with difficulties. C. Low priority Rules that are good to be satisfied. These rules provide a supplementary solution to improve the accessibility. Unless they are satisfied, accessing the content may be somewhat difficult. VII. RULES CORPUS The specification assumes that the web document is having a logical Document Object Module (DOM) order to apply the following rules. Also the HTML elements are properly identified using unique ids and each segment of content is properly nested within corresponding elements. A. Rule 1: Text alternative for multimedia content The images, audio and video that represent some information about the content of the web site should have alternative description in text. 488 B. Rule 2: Text description for colour cues and phrase elements Colours or phrase elements are often used to indicate some clues about the web content. But such indications do not provide any semantic and not supported by assistive technology (AT). Such cues should be replaced by text descriptions to convey the purpose. C. Rule 3: Caption and summary for data tables Reading tabular data going through each cell is not user friendly for visually impaired users. Most of the time it is sufficient to provide a summary of the table content with a meaningful caption to express the information. Users should be able to skip when going through a table if they do not want. D. Rule 4: Proper labelling for form controls Understanding and interacting with form elements is a very significant task. In order to give proper meaning of each form control it is required to use labels and titles accordingly. E. Rule 5: Enhanced visual presentation of text The visual presentation of text can be enhanced by means of basic formatting techniques. These special presentation techniques can be applied on text when they receive the focus or by default. This will enable users with low vision to see the content easily. Standards are as follows; Make relative font sizes (most browsers inherent zooming). Text is not justified (e.g. content in English should be aligned to left margin). At least 1.5 line spacing. Increase letter spacing. F. Rule 6: Contrast colour for visual cues Colours can be used to provide additional visual cues and highlight the important content. In this case colours should be selected carefully in such a way that they conform the contrast ratios. Colours that would provide 3:1 contrast with black words and 5:1 contrast with a white background are more suitable to use. G. Rule 7: Keyboard control for functionality All the functionality on a web site should be provided with the keyboard access. Generally the functions that require keyboard accessibility include form controls and special functions defined under event handlers. The mouse event handlers should also be handled by the corresponding keyboard event handlers.

4 H. Rule 8: Bypass repeated content Some contents in web sites are repeated over all the pages. For example introduction sections and navigation lists. Users should be provided with a mechanism to skip repeated content by enabling it to be expanded or collapsed under user control. I. Rule 9: Meaningful page title Web pages should have titles that describe topic or purpose. Title should be short and unique within the web site and identify the subject of the web page. J. Rule 10: Purposeful link text The purpose of each link should be able to be identified from link text alone. The description should distinguish this link from other links in the web page and help the user to determine whether to follow the link. The URI of the destination is generally not sufficiently descriptive. K. Rule 11: List of content Each web page should have a mechanism to express an overview of the document's contents and organization. In most of the cases, a special list of content can be used for visually impaired users in addition to general navigation of the web site. A list of contents provides links to different sections. Those sections could be located on the same web page or spread across multiple web pages. But together, they should have a complete idea. L. Rule 12: Sequential navigation Generally the pages in a web site have relations with other pages. In most of the cases, it is possible to define a sequential navigation order linking the web pages in a site. Usually web sites have a main navigation list. In addition to that, visually impaired users can be provided with special navigation elements that offer easier ways to go through the content. Such a mechanism will assist in locating the users current position in the site map as well. M. Rule 13: Explanations for abbreviations The information necessary to understand the abbreviations appear on the document should be provided. An abbreviation is the shortened form of a word, phrase, or name. For most abbreviations, providing the full word, phrase, or name is sufficient. But for some abbreviations providing an explanation is more understandable than providing the expansion. N. Rule 14: Input assistance using ARIA Users should be provided with mechanisms to enter correct inputs without leading to errors. In addition to conventional input data validations, special properties can be used to add semantics that are supported by AT. O. Rule 15: Tab order to receive focus The order of content presented to AT should allow the user to make sense of the content regardless of the order when rendered visually. The interactive elements like form controls and links receive the focus by default. Therefore those should be placed in an ordered manner that follows sequences and relationships in the content. Generally tab orders should be explicitly defined on other elements to receive focus in proper order. VIII. SOLUTION: WEB ACCESSIBILITY GENERATOR Web Accessibility Generator is not yet another accessibility evaluation tool. It aims to be a comprehensive framework that can be followed by web developers when developing and modifying web sites to achieve accessibility. Web Accessibility Generator provides the options to evaluate a selected web source code, retrieve details regarding reported issues, apply changes accordingly and monitor the overall progress all in one place. The distinctive features of this solution are as follows; The accessibility rules are specifically targeting visually impaired users requirements and categorized based on the different types of visual impairments. Providing assistance to web developers with guidelines and methods to implement accessibility features in addition to evaluation. Ability to use simply as a platform and browser independent local web application. Easy to understand and provides interactive development environment. An open source framework that is extensible with more accessibility features in the future. 489

5 A. System Architecture The data objects are the instances in the system that provides details about the accessibility features to the processes. Basically data objects are constructed directly by reading the information from the knowledge base. Knowledge base represents a collection of information about each web accessibility feature. A standard Knowledge base API is defined in such a manner that it can be extended with much more accessibility features supplied by external databases. The Knowledge base API defines a particular accessibility feature with the following attributes; Title of the accessibility feature, Priority level, Applicable disability, Description and the Solution. Fig: 8.1. High level system architecture The design of the tool adapts the Model-View-Controller (MVC) architecture. The model component holds the object oriented implementations of the defined web accessibility feature specification. It comprises of two significant components namely the Rule engine and the Knowledge base. Web developer, the user of this tool can upload the source code of a web page that needs to make accessible and select an accessibility evaluation criteria based on the visual impairment type and priority level. View Controller component contains the functions that act as the middleware between model objects and view components. Business objects and data objects are implemented in the Model component to manipulate the Rule engine and Knowledge base. The business objects handle all the functions related to the process of the system. Those functions are: filtering the rule base according to the evaluation criteria invoking the scanning of source code and reporting issues constructing and updating the collection of accessibility violations file management The rule engine is a significant entity in the system which contains inferences to evaluate web pages according to the defined web accessibility features. The functionality of each inference is typically reading the source, detecting and reporting the identified accessibility violations with regard to that particular rule. Fig: 8.2. Design of the Knowledge base component IX. RELATED WORKS There are several existing efforts in making the web accessible. ATRC (Adaptive Technology Resource Center) - University of Toronto introduced A-Prompt (Accessibility Prompt) in 2004 which is a desktop based software tool designed to help web authors to improve the usability of web pages created in HTML format [10]. A-Prompt evaluates an HTML web page to identify barriers to accessibility and then provides the web author with options to make the necessary changes. However its execution is limited to the Windows platform. A-Checker (Accessibility-Checker), the successor of A-Prompt was announced in 2006 [11]. A-Checker is used to evaluate HTML content for accessibility problems by entering the location of a web page, uploading an html file, or by pasting the complete HTML source code from a web page. In summary, lot of efforts have been put into injecting accessibility features in operational level i.e. accessibility is added to web sites through an external agent. Only a few attempts have been made on addressing accessibility during web development. 490

6 Part of these efforts is focused in providing a universal guideline for developers to follow. However, it is also important to provide tool support to encourage embracing those guidelines. No platform-independent and flexible tool has yet been developed for this. X. CONCLUSIONS Web is primarily meant for visual consumption; therefore accessing web content has become one of the main deprivations for millions of visually impaired users. Web Accessibility is the umbrella term that expresses the process to which a web site is made usable to all visitors, including those with disabilities. In addition to complying with the law, an accessible web site can bring in huge benefits on to web sites and businesses. In other hand developing accessible applications has become a social responsibility for the software engineering industry today. However developing accessible web sites is a very critical and time-consuming process that requires expertise knowledge regarding the subject. Even though the web developers are provided with standard and legal recommendations, identify and decide the procedures to follow when actually implementing accessible features is a huge challenge. In such a situation the need for a general framework in support of making web sites accessible comes to the forefront. This research project intends to address this scarcity and come up with a software framework that can be used by web developers when implementing the accessibility into their web sites. In the first phase of the project a wide-ranging research is conducted to uncover the different types of visual impaired users and their requirements for web accessibility. Based on the knowledge gathered a specification is defined including the general accessibility features. Afterwards Web Accessibility Generator, the web based software tool is implemented based on the defined specification. That system will assist the web developers in evaluating accessibility issues in a web site and resolving the issues according to the guidelines provided. REFERENCES [1] United Nations. (2006, December) Convention on the Rights of Persons with Disabilities. [Online]. [2] Amanda Hall Ian Laurence Bailey, Visual Impairment: An Overview. New York: American Foundation for the Blind, [3] (2011, October) WHO Visual impairment and blindness. [Online]. [4] Polsdorfer J R. (2001, April) Visual impairment. [Online]. [5] Wolfmaier T G. (1999, March) Designing for the Color-Challenged: A Challenge. [Online]. enged.html [6] Henry S. L, Developed with the Education and Outreach Working Group (EOWG) and the Web Content Accessibility Working Group (WCAG WG). (2011, June) WCAG Overview. [Online]. [7] Cooper M, Craig J. (2011, January) Accessible Rich Internet Applications (WAI-ARIA) 1.0. [Online]. [8] Henry S L. (2005, August) Essential Components of Web Accessibility. [Online]. [9] Arrue M, Fajardo I, Garay N, Tomás J Abascal J, "The use of guidelines to automatically verify Web accessibility," Universal Access in the Information Society, vol. III, pp , [10] Adaptive Technology Resource Center (ATRC) - University of Toronto. (2004) A-Prompt. [Online]. [11] Adaptive Technology Resource Center (ATRC) - University of Toronto. (2006) AChecker. [Online]. [12] Agarwal S, Kumar A Rajput N, "An alternative information web for visually impaired users in developing countries," in 10th international ACM SIGACCESS conference on Computers and accessibility, New York, USA,