I recently presented an Intergen Twilight Session on building applications using Silverlight while remaining compliant with the latest version of the New Zealand Government Web Standards. I’ve posted the slides and demos here.
Version 2.0 of the standards was released March 2009. The standards are now aligned with W3C's WCAG2.0 standards, level AA, plus some additional NZ specific technical standards. Aligning with WCAG 2.0 is a great step as there is a wealth of information and tools out there.
One of the interesting NZ amendments to the WCAG standards (regarding Silverlight at least) is in relation to the use of web technologies in general. The WCAG 2.0 standard states.
Conformance Requirements (WCAG 2.0)
4. Only Accessibility-Supported Ways of Using Technologies: Only accessibility-supported ways of using technologies are relied upon to satisfy the success criteria. Any information or functionality that is provided in a way that is not accessibility supported is also available in a way that is accessibility supported.
"Accessibility Supported” is defined as,
First, the technologies must be designed in a way that user agents including assistive technologies could access all the information they need to present the content to the user. Secondly, the user agents and assistive technologies may need to be redesigned or modified to be able to actually work with these new technologies.
However, the level of assistive technology support needed for accessibility support has not been defined and is described as a “complex topic” and puts the responsibility on the wider community to establish what is acceptable.
The New Zealand Government Web Standards take a more conservative approach.
2.2 Technologies which may be used but not relied on
So this means that regardless of the accessibility features of Silverlight it can not be relied on to provide access to content and services and an alternative must be provided.
In many cases this isn’t too much of an issue. For example, it’s pretty straight forward providing access to a video transcript if the Silverlight plug-in has not been installed on a user’s browser. However, in more complex scenarios the cost of providing an alternative will be prohibitively expensive – it’s hard enough building software within existing budgets without having to double the development effort. There are approaches that can be taken and I’ll post some over the next few weeks.