bruce lawson-html5-aria-japan
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HTML5 and WAI-ARIA
HTML5 Study Groupt/ Tokyo / 18 November 2010
Bruce Lawson, Opera Software
HTML5 hates accessibility?
Accessible Rich Internet Applications
WAI-ARIA is intended to be a bridging technology. It clarifies semantics to assistive technologies when authors create new types of objects, via style and script, that are not yet directly supported by the language of the page.
http://www.w3.org/TR/wai-aria/complete
How assistive technology works
roles, states, properties
● Role is what something is. <div role="navigation">, “tooltip”● State is how something is at the moment (from pre-defined list): aria-checked = “true”, aria-required=”true”● Property: aria-valuenow (of a slider), aria-describedby (points to a description)
HTML attributes don't validate in HTML4
<div role="navigation"> <input aria-required="true">
(but validate in HTML5!)
Built-in always beats bolt-on
It is not appropriate to create objects with style and script when the host language provides a semantic element for that type of objects.
While WAI-ARIA can improve the accessibility of these objects, accessibility is best provided by allowing the user agent to handle the object natively.
Remains useful for legacy content
When native semantics for a given feature become available, it is appropriate for authors to use the native feature and stop using WAI-ARIA for that feature. Legacy content may continue to use WAI-ARIA
HTML5 has "built-in" ARIA
HTML Implied ARIA information<hr> separator
<a href=".."> role=link<input required> aria-required=true
<nav> role=navigation<textarea> role=textbox aria-multiline=true<article> role=article (document/
application / main)<body> role=document / application
<address> role=contentinfo <output> aria-live=polite
Full list: http://dev.w3.org/html5/spec/content-models.html#annotations-for-assistive-technology-products-aria
Gotcha!
●Multiple <header>s allowed, but only one role=banner per page●Multiple <footer>s allowed, multiple <address> allowed but only one role=contentinfo per page●No <main> element●Some screen reader naughtiness
Not everything is native to HTML5
WAI-ARIA is intended to be used as a supplement for native language semantics, not a replacement. When the host language provides a feature that provides equivalent accessibility to the WAI-ARIA feature, use the host language feature.
WAI-ARIA should only be used in cases where the host language lacks the needed role, state, and property indicators.
Validator knows about ARIA
<nav role=main>
Fix ARIA roles in browsers (transitional)
https://github.com/yatil/accessifyhtml5.js
tabindex=-1
Previously doubly illegal, valid HTML5
<h3 tabindex="-1">Destination</h3>
動画 アクセシビリティvideo accessibility
<video controls autoplay poster=… width=… height=…><source src=movie.webm type=video/webm><source src=movie.mp4 type=video/mp4><source src=movie.ogv type=video/ogg><track src=subtitles.srt kind=subtitles srclang=ja><!-- fallback content -->
</video>
www.bit.ly/websrt - <track> element faked in JavaScripthttp://www.delphiki.com/websrt/ - webSRT formal explainedhttp://www.delphiki.com/html5/playr/ - very nice video and <track> playerhttp://www.whatwg.org/specs/web-apps/current-work/multipage/video.html#the-track-element
Essential reading
● WAI-ARIA導入（日本語訳）http://d.hatena.ne.jp/aratako0/20090709/p1
● HTML5 and the myth of WAI-ARIA redundance (ARIA roles and properties not available in HTML5)http://www.paciellogroup.com/blog/?p=585
● ARIA spec http://www.w3.org/TR/wai-aria/complete
www.opera.com/developerbruce.lawson@opera.comwww.brucelawson.co.uk
twitter.com/brucel
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