Web Accessibility

Since the rapid growing web become popular as time goes by, the main information

communication shifted from the traditional television to the Internet. The longer usage time, the more exposed time we spend and rich media act as role as television.

The World Wide Web become rich-providing information source since people sharing and interaction activities is getting more and more. However, the usability isn’t equally increasing for people with disability to access the web effectively. There are three main categories to indicate: authoring tools, browser and context [5].

1. Context is designed to be accessible.

2. Browser and multimedia player provide usable and accessible experience.

3. Authoring tool include content management system (CMS) such as blogging system and other tool to generate web content

Figure 2-3 Components of Web Accessibility

Figure 2-3 illustrates the componet of web accessiblity. Developer is refered to be the content producer using authoring tools such as CMS. User is the information comsumer as the end point of data flow using browser media players. It’s clear that content is the middle product

and is required whole componenets are accesiable.

Figure 2-4 Cycle of Accessibility Implementation

Figure 2-4 shows us how to implement accessibility. It’s a cycle of chicken and egg. New feature implementation by authoring tools needs support by browser and media player. In the other hand, browser and media player wait for a critical mass of authoring tools to use a new feature to get accessibility better.

Figure 2-5 Components and Guidelines for Web Accessibility

Figure 2-5 shows the entire components of web accessibility. These components are bringing together by the web accessibility initiative (WAI) of World Wide Web consortium (W3C).

W3C is helping coordinate international web accessibility effort. WAI work with three guidelines for implementation of W3C specification.

1. Authoring Tool Accessibility Guidelines (ATAG),

2. User Agent Accessibility Guidelines (UAAG);

3. Web Content Accessibility Guidelines (WCAG);

ATAG 1.0 was published in February 2000 and ATAG 2.0 Working Draft was released in 21 May 2009 [16]. ATAG is primitively written for authoring tools to produce accessible content via an accessible authoring interface. Intending to meet the need of many different audiences, ATAG and supporting documents is very important for people who want to choose more accessible authoring tools and people who want their authoring tools to improve accessibility in the future version.

UAAG 1.0 was published in February 2000 and UAAG working Draft was released in 11 March 2009 [17]. UAAG explain how to make user agent such as browser and media player more accessible to people with disability. UAAG is primitively for developer of web browser, media player and other user agent used by user. UAAG and supporting documents intend to meet the need of people who want to choose user agent more accessible and people who want their use agent improve accessibility.

WCAG 1.0 was published in May 1999 [18]. WCAG explain how to make web content more accessible to people with disability. It’s not only targeted primitively for content producer but also used by authoring tools developer, user agent developer and evaluation tools developer.

Authoring tools developer use it to create tools that generate accessible content, user agent developer use it to create tool s utilize accessible content and evaluation tools developer use it to create tools discovering accessibility issue of the content.

Since WCAG 1.0 was published, many organizations adopted WCAG 1.0 in their policy, and these feedbacks from, developer or policy maker form the basis of WCAG 2.0 that was released in 11 December 2008. WCAG 2.0 Is different from WCAG 1.0 by introducing a new concept called priority scheme. Priority scheme define testable success criteria, remove technology-specific information and provide testable information in checklist. In additional to

the testable information, it also provides an overview of materials for user to orient the suite of documentation.

Here list flicker related guideline referred in WCAG 1.0 and WCAG 2.0.

WCAG 1.0

Checkpoints: 7.1 Until user agents allow users to control flickering, avoid causing the screen to flicker. [Priority 1]

Note. People with photosensitive epilepsy can have seizures triggered by flickering or flashing in the 4 to 59 flashes per second (Hertz) range with a peak sensitivity at 20 flashes per second as well as quick changes from dark to light (like strobe lights).

WCAG 2.0

Guideline 2.3 Seizures: Do not design content in a way that is known to cause seizures.

2.3.1 Three Flashes or Below Threshold: Web pages do not contain anything that flashes more than three times in any one second period, or the flash is below the general flash and red flash thresholds. (Level A)

Note: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether it is used to meet other success criteria or not) must meet this success criterion. See Conformance Requirement 5: Non-Interference.

2.3.2 Three Flashes: Web pages do not contain anything that flashes more than three times in any one second period. (Level AAA)

The detail descriptions in guideline 2.3.1 of WCAG2.0 have defined some keyword such like relative luminance, blinking, flash and red flash. Relative luminance is the relative brightness of any point in a color space and usually normalized to 0 for darkest black and 1 for lightest white. Blinking is a visual effort switch back and forth between two visual states in a way that is meant to draw attention. Flash is a pair of opposing changes in relative luminance that can cause seizures in some people. What make blinking differ from flash is the volume and

frequency. Flash is more dangerous to cause seizures if it is large enough and in the right frequency range.