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1Yahoo! Confidential
Yahoo! Experiences with Accessibility, DHTML, and Ajax
in Rich Internet Applications
CSUN, March 23rd, 2006
Victor Tsaran – Accessibility Project Manager, Yahoo! Inc.Nate Koechley – Senior Engineer & Design Liaison, Yahoo! Inc.
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Agenda
• Changing Landscape
• Definitions
• Four Approaches– Standards-based development
– Redundant interfaces
– Thorough, fortified interfaces
– “Accessible DHTML”
• Looking Ahead
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About Us
• Victor Tsaran
– Accessibility Project Manager
• Nate Koechley
– Senior Frontend Engineer
– Technical Architect and Design Liaison
– Presentation Platform Team
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What’s Happening?
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Browser vs. Desktop
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Web 1.0 vs. Web 2.0
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Yahoo’s “Alan Cooper” Model
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Definitions
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Definitions:DHTML
• DHTML is – markup and style made interactive and
dynamic through script• Generally, DHTML is JavaScript modifying CSS,
HTML and the DOM
• DHTML is not – a specific technology
– inherently inaccessible
– new
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Definitions:AJAX / Ajax
• Asynchronous JavaScript and XML• the ability to talk to the server without tearing down the
existing page
• the ability to update part of the page
• Ajax is not – a specific technology
– inherently inaccessible
– new
• No server requests = it’s not Ajax
• AJAX is a subset of Ajax
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Definitions:Rich Internet Applications (RIAs)
• Rich Internet Applications are:
– web apps with features and functionality of traditional desktop applications
– usable from any internet terminal – no installation required
– can be created in various languages: Flash, JavaScript, Java
• today’s talk is focused on JavaScript RIAs
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Definitions:Accessibility
• Accessibility is:
– “A general term used to describe the degree to which a system is usable by as many people as possible without modification”
(cite: wikipedia)
• Often, our focus is on enabling screen-readers specifically
– However, the resulting work in generally more far-reaching
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What about Desktop Accessibility?
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Accessibility on the Desktop
• Through various APIs…– Microsoft’s Active Accessibility (MSAA)
– Sun’s Java Access Bridge
– Accessibility Toolkit for Linux (ATK)
• …Software communicates to the operating system, which communicates with assistive technology.
• Highly effective, resulting in nearly omnipresent accessibility.
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But what about web accessibility?
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Accessibility on the Web (1)
• Some information is provided to the desktop API
– The Document Object Model (DOM) provides static information via semantic elements and attributes
• But…
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Accessibility on the Web (2)
• … but the depth of necessary information is missing
– Role, state, actions, caret, selection, children, relations, changes…
• And so are inputs and outputs
– keyboard, focus, blur, change, updates.
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So how can we move forward?
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Four Techniques – Use ‘em All
1. Standards-based development
2. Redundant interfaces
3. Thorough, fortified interfaces
4. “Accessible DHTML”
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Approach 1:Standards-based development
• Overview and Definition
• Subsequent layers enhance meaningful and structured markup
• Progressive and unobtrusive enhancement
• Make each layer a strong foundation
• Don’t corrupt neighboring layers
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Approach 1:Standards-based development
• Examples
• Tab box is really anchored links and lists – well marked up content, available to all
• Unobtrusive JavaScript doesn’t Hijax links when it shouldn’t
• Stretching semantics to provide clues
• Microformats enrich date, and provide predictable hooks for add-ons
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Approach 1:Standards-based development
• Example: Tab-Panel box: complete
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Approach 1:Standards-based development
• Example: Tab-Panel box: no CSS
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Approach 1:Standards-based development
• Example: Tab-Panel box: no JavaScript
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Approach 1:Standards-based development
• Benefits
• Should be doing this regardless
• Truly available to all
• The foundation of better things
• Works “with the grain” of web technologies
• A step toward a semantic web
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Approach 1:Standards-based development
• Drawbacks
• Doesn’t solve every problem
• Perceived overhead
• Unobtrusive JavaScript and Hijax are still less familiar techniques
• Be careful not to step on event handlers
• Only trap clicks when appropriate
• Server must reply to both partial and complete requests from the client
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Approach 2:Redundant interfaces
• Overview and Definition
• Multiple means of input• GUI input vs. alphanumeric input
• Direct movement of objects vs. form-based movement
• Multiple means of manipulation• Keyboard vs. Mouse
• Esc vs. Cancel
• Drag-drop vs. form-based
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Approach 2:Redundant interfaces
• Example, 1D Slider Input
• Simple support for vertical and horizontal sliders as a direct-manipulation alternative to input boxes
• Enhances the basic input box, but need not replace it.
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Approach 2:Redundant interfaces
• Example, 2D Slider Input
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Approach 2:Redundant interfaces
• Example: Calendar Date Selector
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Approach 2:Redundant interfaces
• Benefits
• Better for everybody• Keyboard is important for ALL users
• Provide multiple familiar task paths
• Transfer the complete set of expectations from the desktop to the browser
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Approach 2:Redundant interfaces
• Drawbacks
• Cannot fully communicate with the desktop’s accessibility APIs
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Approach 3:Thorough, fortified interfaces
• Overview and Definition
• Now is the time to lay a new foundation
• Libraries and platforms must support all comers
• Not just the mouse, not just the keyboard• Not just one key, but all keys
• Must offer a faithful and complete experience
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Approach 3:Thorough, fortified interfaces
• Examples
• Menu
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Approach 3:Thorough, fortified interfaces
• Example: Slider w/ Keyboard Controls
– keyboard in addition to mouse controls
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Approach 3:Thorough, fortified interfaces
• Benefits
• More options for everybody
• Supports many working styles
• Establish the new platform• My prediction: new platform will last much longer
than the 10 years of the previous platform
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Approach 3:Thorough, fortified interfaces
• Drawbacks
• Isn’t easy
• Clients don’t always notice• Requires personal integrity and commitment
• Seems more complete and heavy
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Approach 4:“Accessible DHTML”
• Overview and Definition– IBM technology, now in W3C and open
• http://www.w3.org/WAI/PF/adaptable/HTML4/embedding-20060318.html
– Allows embedded role and state metadata in HTML documents
– Uses namespace extensions to XHTML 2, but• Techniques allow most functionality in HTML 4 documents,
as of today
– Communicate directly with the desktop API
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Approach 4:“Accessible DHTML”
• Examples: XHTML 2
<html xmlns:wairole="/w3.org/2005/01/wai-rdf/GUIRoleTaxonomy#" xmlns:waistate=“/w3.org/2005/07/aaa">
<span id="slider" class="myslider"role="wairole:slider"waistate:valuemin="0"waistate:valuemax="50"waistate:valuenow="33"> </span>
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Approach 4:“Accessible DHTML”
• Examples: HTML 4
<script type="text/javascript" src="enable.js"></script>
<span id="slider" class="myslider myselector2 slider valuemin-0 valuemax-50 valuenow-33" tabindex="0" >
</span>
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Approach 4:“Accessible DHTML”
• Benefits
– Utilizes powerful and well-understood desktop API
– Map controls, events, roles and states directly to powerful and well-understood desktop accessibility APIs
– Enriches markup in standard way
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Approach 4:“Accessible DHTML”
• Drawbacks
– Requires recent-version of assistive technology software (e.g., screen reader)
– Only works in Mozilla’s Firefox 1.5+ today• Not in Microsoft’s IE 7, or others
– XHTML required for full power• HTML does not allow multiple states, for example
– Emerging technology
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Looking ahead…
• What is at risk if we don’t standardize on an accessible platform?
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Open Questions
• Is there always an alternative to a mouse-based experience? (for example, with the mouse I can reorder the toolbars in MSWord. I’m not sure if this is possible without a mouse, or even necessary.)
• Partial-page updates remain difficult to communicate to the screen reader’s DOM buffer.
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More Information
• Nate Koechley – – natek@yahoo-inc.com
– http://nate.koechley.com/blog
• Victor Tsaran– vtsaran@yahoo-inc.com
• Yahoo! Developer Network and Y! UI Blog:– http://developer.yahoo.net
– http://developer.yahoo.net/yui
– http://developer.yahoo.net/ypatterns
– http://groups.yahoo.com/group/ydn-javascript
– http://www.yuiblog.com
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END OF TALK
• NOTE: Remaining slides are candidates for inclusion, but will likely be dropped from the presentation.
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Slider
• Slider Control– Simple support for vertical and horizontal sliders as a direct-
manipulation alternative to input boxes
– Simple API to script onChange behavior
– Support for smooth or graduated slider action
– Built-in support for click-to animation of slider
– Builds on top of:• Drag and Drop Utility
• Position Utility
• Animation Utility (optional)
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Slider
• Slider: Beyond the Obvious– Look to desktop applications for inspiration for slider
applications
– Generally, consider a slider as an alternative to entering values that run along a continuum; for example:
• RGB values for color selection
• Amplitude of different variables in a prioritization algorithm
• Simple integer continuum
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Slider
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Calendar
• Calendar– Simple date selection widget that can be implemented with
only a few lines of code
– Fully client-side calendar navigation
– Built-in multi-select or single-select capability, in single or two-up views
– Out-of-the-box rich UED-approved look-and-feel standard across the Yahoo! Network
– Support for advanced implementations such as:• localization
• blacked-out date sets
• custom holiday formatting
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Calendar
<script> var myCal; function init() { myCal = new ygCalendar(‘myCal’,’myCalContainer’); myCal.render(); }</script><div id=‘myCalContainer’></div>
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Calendar
• Calendar: Beyond the Obvious– Highly adaptable API allows you to use the Calendar Widget as visual
container for any data that can be organized by date —
• Flickr photo album
• Upcoming.org events
• Blog posts and comments
– CSS styles can be overridden to develop custom styling for specific properties
– The calendar’s advanced render stack allows the content of any given date cell to be dynamically altered by extending the base class, ygCalendar_Core, and using one or more callback functions
– Other advanced options like minimum and maximum selection dates, week numbers, and which day the week begins on can be changed using the built-in configuration options
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AutoComplete
• AutoComplete– Provides “as-you-type” list of matching items
– List navigable via the mouse or keyboard
– Configurable dropdown styles and animation
– Data subset cache
– Configurable delay prior to lookup
– “Starts with” or “Contains” matching patterns
– Limit-to-list feature (combo box vs. select box)
– Common and custom data formats supported:• Delimited text
• JavaScript Array literals
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AutoComplete
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TreeView
• TreeView Control– Flexible support for hierarchical information views:
• Table of contents
• Threaded discussion
• Hierarchical Menus
– API gives you easy scripting access to interesting moments:• When nodes are clicked
• When nodes expand
• When nodes contract
– Support for dynamic loading of node contents
– Styling driven entirely by CSS
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TreeView
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