[contents]
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This document specifies Best Practices for delivering accessible rich internet applications using WAI-ARIA [ARIA]. The principle objective is to produce a usable, accessible experience over the Web. It provides recommended approaches to create accessible Web content using WAI-ARIA roles, states, and properties to make widgets, navigation, and behaviors accessible. The document also describes considerations that might not be evident to most implementers from the WAI-ARIA specification alone. This document is directed primarily to Web application developers, but the guidance is also useful to user agent and assistive technology developers. This document is part of the WAI-ARIA suite described in the ARIA Overview.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.
This document is a Public Working Draft by the Protocols & Formats Working Group of the Web Accessibility Initiative. It supports the Accessible Rich Internet Applications (WAI-ARIA) [ARIA] specification, providing detailed advice and examples beyond what would be appropriate to a technical specification but which are important to understand the specification. Most Web content developers seeking to accomplish particular tasks in rich Web content, and make their content accessible, should follow the approaches in this document to accomplish their task.
Feedback on the information provided here is essential to the ultimate success of Rich Internet Applications that afford full access to their information and operations. The PFWG asks in particular:
Comments on this document may be sent to public-pfwg-comments@w3.org (Archive). Comments should be made by 24 March 2009. However, comments arriving after that date will still be considered. In-progress updates to the document may be viewed in the publicly visible editors' draft.
Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. The group does not expect this document to become a W3C Recommendation. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
The disclosure obligations of the Participants of this group are described in the charter.
This section is informative.
The WAI-ARIA Best Practices guide is intended to provide readers with an understanding of how to use WAI-ARIA to create an accessible Rich Internet Application. As explained in the WAI-ARIA Primer, accessibility deficiencies in today's markup render rich internet applications unusable by people who use assistive technologies (AT) or who rely on keyboard navigation. The W3C Web Accessibility Initiative's (WAI) Protocols and Formats working group (PFWG) plans to address these deficiencies through several W3C standards efforts, with a focus on the ARIA specifications.
For an introduction to WAI-ARIA, see the Accessible Rich Internet Applications Suite (WAI-ARIA) Overview. The WAI-ARIA Best Practices is part of a set of resources that support the WAI-ARIA specification. The Best Practices describe recommended usage patterns for Web content developers, and the WAI-ARIA Primer [ARIA-PRIMER] provides a basic introduction to the concepts behind and reason for ARIA. The WAI-ARIA Suite fills gaps identified by the Roadmap for Accessible Rich Internet Applications (WAI-ARIA Roadmap) [ARIA-ROADMAP]. These documents serve as important places of clarification where topics appear to be unclear.
With the conceptual basis provided in the WAI-ARIA Primer, you should have a good understanding of how ARIA provides for interoperability with assistive technologies and support for a more usable, accessible experience. This guide begins by providing some general steps for building an accessible widget using ARIA, script, and CSS. It then extends your knowledge of ARIA with detailed guidance on how to make rich internet applications keyboard accessible. Next, the scope widens to include the full application, addressing necessary layout and structural semantics within the Web page. These semantics are critical to enable assistive technologies to provide a usable experience when processing rich internet applications with rich documents on the same page. It includes guidance on dynamic document management; use of ARIA Form properties; ARIA Drag and Drop; and then the creation of ARIA-enabled alerts and dialogs. The appendix provides substantial reference information including code samples for developers of user agents, assistive technologies, and Web pages.
WAI-ARIA markup is currently not included in (X)HTML. The W3C WAI PF working group will be creating DTDs for XHTML 1.0 and HTML 4.01 for those wishing to validate their markup with WAI-ARIA embedded into these host languages.
At this point you should have a basic understanding of how ARIA is used to support interoperability with assistive technologies. If you are not reusing an existing ARIA-enabled widget library and wish to create your own the following steps will guide you through the thought process for creating an accessible widget using ARIA.
Pick the widget type (role) from the ARIA taxonomy
ARIA provides a role taxonomy ([ARIA], Section 3.4) constituting the most common UI component types. Choose the role type from the provided table. If your desire was to create a toolbar set the role to toolbar:
<div role="toolbar">
Once you have chosen the role of your widget, consult the WAI-ARIA specification [ARIA] for an in-depth definition for the role in to find the supported states, properties, and other attributes. For example, the toolbar role definition includes:
toolbar there are no such states or properties. However, in the case of a listbox, you may choose to set the property of aria-multiselectable to true if you were to have more than one item in the listitem selected at a time. This indicates to the assistive technology that the listbox manages a collection of selectable options.Once you have chosen the states and properties that apply to your widget you must set those properties you will use to set their initial values. Note: You do not need to use all the states and properties available for your role. In our case we shall use:
<div role="toolbar" multiselectable="false" tabindex="-1" id="customToolbar" onkeydown="return optionKeyEvent(event);" onkeypress="return optionKeyEvent(event);" onblur="hideFocus()" onfocus="showFocus()" > <img src="img/btn1.gif" tabindex="0" title="Home" role="button" id="b1" alt="Home" onClick="updateText('Home was invoked');"> <img src="img/btn2.gif" tabindex="-1" title="Refresh" role="button" id="b2" alt="Refresh" onClick="updateText('Refresh was invoked');"> <img src="img/btn3.gif" tabindex="-1" title="Help" role="button" id="b3" alt="Help" onClick="updateText('Help was invoked');"> </div>
By setting tabindex="-1" on the toolbar , we have specified that the toolbar will receive focus in the document order. By setting tabindex="1", on the first button we have chosen to have the first child object to receive focus when the toolbar (parent) receives focus.
Important: When embedding WAI-ARIA markup in (X) HTML, all ARIA states and properties must be preceded with the characters aria- with the exception of the role and tabindex attributes. Otherwise, the user agent will not map the WAI-ARIA information, resulting in it not being recognized by assistive technologies.
When embedding WAI-ARIA into other host languages, tabindex does not carry over. The WAI-ARIA tabindex extensions are specific to (X)HTML to repair deficiencies in keyboard support.
Assistive technologies are very dependent on the structure of widgets as well as general document structure. Structure provides context to the user. A toolbar is a collection of common functions made available to the user. Therefore, all functions you would like in the toolbar must be contained within it. This can be determined by using the Document Object Model [DOM] tree structure created by the browser when parsing the host language. By using the parent child relationship of the DOM, an assistive technology can determine all the related toolbar widgets associated with the toolbar. The toolbar widgets would be DOM children of the "toolbar" container. For our purposes we will define three image buttons for cut, copy, and paste.
<div role="toolbar" tabindex="0" aria-activedescendant="button1"> <img src="buttoncut"><img src="buttoncopy"><img src="buttonpaste"> </div>
We now need to assign the roles and states for each of the children. However, we shall save the detailed navigation for step 5.
<div role="toolbar" tabindex="0" aria-activedescendant="button1"> <img src="buttoncut.png" role="button" id="button1"> <img src="buttoncopy.png" role="button" id="button2"> <img src="buttonpaste.png" role="button" id="button3"> </div>
The process of setting roles and states may be a recursive procedure if the children themselves have children, such as in the case of an expandable/collapsible tree widget.
Establish keyboard navigation of the widget and plan for how it will be navigated to within the document
It is very important that that your widget be keyboard accessible. In fact, there must also be a keyboard equivalent for every mouse operation. Where possible you should refer to the WAI-ARIA examples in this guide for tips on how to implement keyboard navigation for your widget. If you find that an example is not provided, you should follow standard keyboard bindings for UI components such as those used for the Java Foundation Classes for Windows 95/NT.
For our toolbar, we have chosen to have the toolbar manage the focus for its children and through the use of the aria-activedescendant property. We have also chose to have the toolbar receive focus based on the tab order by using tabindex. In order to use aria-activedescendant, each descendant must have an assigned ID.
<head>
<script>
...
function optionKeyEvent(event)
{
var tb = event.target;
var buttonid;
DOM_VK_ENTER = 13;
// Partial sample code for processing arrow keys
if (event.type == "keydown") {
if (event.altKey) {
return true; // Browser should use this, the menu view doesn't need alt-modified keys
}
// XXX Implement circular keyboard navigation within the toolbar buttons
if (event.keyCode == DOM_VK_ENTER) {
ExecuteButtonAction(getCurrentButtonID(); // This is an author defined function
}
else if (event.keyCode == event.DOM_VK_RIGHT) {
// Change the active toolbar button to the one to the right (circular) by
var buttonid = getNextButtonID(); // This is an author defined function
tb.setAttribute("aria-activedescendant", buttonid);
}
else if (event.keyCode == event.DOM_VK_LEFT) {
// Change the active toolbar button to the one to the left (circular) by
var buttonid = getPrevButtonID(); // This is an author defined function
tb.setAttribute("aria-activedescendant", buttonid);
}
else {
return return true;
}
return false;
}
else if (event.type == "keypress") {
...
}
}
</script>
<div role="toolbar" tabindex="0" aria-activedescendant="button1" id="tb1"
onkeydown="return optionKeyEvent(event);"
onkeypress="return optionKeyEvent(event);">
<img src="buttoncut.png" role="button" id="button1">
<img src="buttoncopy.png" role="button" id="button2">
<img src="buttonpaste.png" role="button" id="button3">
</div>
The details of implementing keyboard navigation are described in Keyboard and Structural Navigation section of this document.
Note: You must also show the visual focus for each element that has focus.
Apply and and manage needed ARIA states in response to user input events
Similar to the processing of aria-activedescendant in Step 5, as author you must set any additional ARIA states and properties on document elements.
Synchronize the visual UI with accessibility states and properties for supporting user agents
You should consider binding user interface changes directly to changes in WAI-ARIA states and properties, such as through the use of CSS attribute selectors. For example, the setting of the aria-selected state may change the background of a selected treeitem in a tree. This may also be done with JavaScript.
.treeitem[role="treeitem"][aria-selected="true"] {color: white; background-color: #222222;}
.treeitem[role="treeitem"][aria-selected="false"] {color: white; background-color: beige;}
Authors should be aware that CSS attribute selectors are not supported in some browsers. For example, although it is supported in Firefox 2, it is not in Internet Explorer until version 7. In Internet Explorer 6 or earlier you should set the WAI-ARIA state or property and then apply the updated style information using script. Internet Explorer 7 supports CSS attribute selectors but then you need to refresh the style using element.className +="".The following example shows how to refresh the styling for a change the selected class attribute in a WAI-ARIA menu item in Internet Explorer 7.
function setSelectedOption(menuItem)
{
if (menuItem.getAttribute("role") != "menuitem") {
alert("Not a menu item");
return;
}
var menu = getMenu(menuItem);
var oldMenuItem = getSelectedOption(menu);
// Set class so that we show selection appearance
oldMenuItem.removeAttribute("class");
menuItem.setAttribute("class", "selected");
menu.setAttribute("aria-activedescendant", menuItem.id);
menuItem.className += "";
}
The proper synchronization showing and hiding sections in a widget with the ARIA display state is also critical. Some platform accessibility APIs provide events for applications to notify the assistive technology when pop-ups such as menus, alerts, and dialogs come into view or go away. Rich Internet applications can assist browsers which support these conventions by:
Creating an entire section and then insert it into the Document Object Model [DOM], as a subtree of the parent element activated to show the pop-up, and then removing the section from the inserted area when the pop-up goes away.
OR
Using the following style sheet properties to show and hide document sections being used to represent the pop-up items, menus or dialogs:
display:blockdisplay:nonevisibility:visiblevisibility:hiddenBy monitoring these behaviors a user agent may use this information to notify assistive technology that the pop-up has occurred by generating the appropriate accessibility API event.
Some assistive technologies may use the DOM directly to determine these when pop-up occurs. In this case, the first mechanism of writing a section to the DOM would work using the DOM events as demonstrated here.
// create new table row with table cell and div
var newTr = document.createElement('TR');
var newTd = document.createElement('TD');
var newDiv = document.createElement('DIV');
newTr.appendChild(newTd);
newTd.appendChild(newDiv);
//insert this new table row before the Node selected
var container = theNode.parentNode;
container.insertBefore(newTr, theNode);
//remove theNode selected
container.removeChild(theNode);"
However, if you are using CSS to show and hide sections of the DOM (2) it is essential that you set the corresponding ARIA aria-hidden property to indicate that the section is visible or hidden and synchronize it with your CSS styling as shown here:
[aria-hidden=true] {visibility: hidden;}
...
<div role="button" aria-haspopup="true" aria-owns="mypopupmenu">
<div role="menu" aria-hidden="true" id="mypopupmenu">...</div>
When an image is used to represent information within a component, such as image buttons, you need to set the alternative text on those images. This is then mapped by the user agent to the accessible name in the platform accessibility API. It also ensures that visual focus is indicated when the element receives focus. Using our example:
<div role="toolbar" tabindex="0" aria-activedescendant="button1" id="tb1" onkeydown="return optionKeyEvent(event);" onkeypress="return optionKeyEvent(event);"> <img src="buttoncut" role="button" id="button1" alt="cut"> <img src="buttoncopy" role="button" id="button2" alt="copy"> <img src="buttonpaste" role="button" id="button3" alt="paste"> </div>
Once you have made the basic widget accessible you may then need to establish its relationship to other widgets. Examples of this are aria-labelledby, aria-controls, aria-describedby and aria-flowto. The details of using these relationships are described in the Relationships section of this document.
Other relationships which should be considered are more declarative and provide context to the widget within a set. For these, aria-level, aria-posinset, and aria-setsize are provided. If you structure your Document Object Model appropriately so that the user agent can determine this information from it directly, using the DOM hierarchy you do not need to set these properties. There are, however, situations in rich internet applications where all the elements in a container are not in the DOM at one time, such as when you can only render the ten of fifty items in a subtree. In this case the user agent cannot determine the number of tree items (aria-setsize) for the position in the set (aria-posinset), and potentially the tree depth (aria-level) from the DOM. In these situations you will need to provide these WAI-ARIA properties.
Review widget to ensure that you have not hard coded sizes
The ability for applications to respond to system font settings is a requirement. Most user agents are designed to meet this requirement. This also means your Web application running within your browser is impacted when the user agent changes the font sizes to meet the need. If you have hard coded your font size in pixels an increase in system fonts will not be reflected in your Web application. You must also not hard code the size of your widgets in pixels either. If the fonts are scalable, but the widget they are encapsulated in is not, then the text could flow outside your widget.
Follow these rules to allow your application to respond to system font settings:
An em is a is the font unit of measure between the top and bottom of an upper case letter M. This is independent of the scale which the font is reproduced. Often, the user agents font adjustment to system settings, are such that they are defined using the font's internal metrical units (font units), which are specified as units of the total body or em height of the font, hence em units. Em can be used as a proportional unit of length in CSS to scale properties in relation to the default font size settings in a users' browser.
Important: Most browsers today have a zoom feature which allow the user to magnify the entire Web page. Most legislation today requires that your application respond to system font and color settings and therefore you will want to consider the fact the system settings could adversely effect your Web page should you decide to hard code pixel sizes.
To ensure you have set your WAI-ARIA semantics correctly, test your application with your user agent, an assistive technology, and a person with disability. Example assistive technologies are screen readers and screen magnifiers. Ensure that your user agent is designed to support WAI-ARIA and their your assistive technology is designed to support ARIA in the selected user agent.
Finding people with disabilities to do testing may be difficult but many companies employ people with disabilities, including your customers, and you should reach out to them to ask for help. Other places to look are advocacy groups like the National Federation of the Blind or your local schools for the blind, reading and learning centers, and so on. The people you reach out to may someday need to use what you produce.
Providing an effective navigation experience to the user is critical for usability. This section starts with guidance on how to provide effective keyboard navigation for widgets in a Rich Internet Application environment. This includes a discussion on how to manage keyboard focus and the specifics on providing keyboard navigation for tooltips. This is is followed by a broader discussion on how to convey structural semantics for the entire Web page. These semantics help an assistive technology provide additional navigation, increase user productivity, and render the page in an alternative formats. This rendering may be in different forms, including but not limited to speech, page restructuring, and alternative input solutions.
One way to provide keyboard support in (X)HTML is with form and list elements that accept keyboard focus by default. With the Tab key, the user can navigate to these types of elements. However, when building sophisticated widgets, it's necessary to be able to control keyboard navigation exactly. Authors may require or prefer to use host language elements that do not have built-in keyboard navigation features. For example, the author may wish to provide keyboard navigation without altering the tab order. Navigating within large composite widgets such as tree views, menubars, and spreadsheets can be very tedious and is inconsistent with what users are familiar with in their desktop counterparts. The solution is to provide full keyboard support using the arrow keys to provide more intuitive navigation to provide navigation within the widget, while allowing Tab and Shift+Tab to move focus out of the widget to the next place in the tab order.
A tenet of keyboard accessibility is reliable, persistent indication of focus. The author is responsible, in the scripts, for maintaining visual and programmatic focus and observing accessible behavior rules. Screen readers and keyboard-only users rely on focus to operate rich internet applications with the keyboard.
One requirement for supporting the keyboard is to allow focus to be set to any element. The tabindex attribute can be used to include additional elements in the tab order and to set programmatic focus to them. Originally implemented in Internet Explorer 5, the feature has been extended to Opera, Firefox, and Mozilla. The following table outlines the use of the tabindex attribute:
| Tabindex Attribute | Focusable with mouse or JavaScript via element.focus() | Tab Navigation |
|---|---|---|
not present | Follows default behavior of element (only form controls and anchors can receive focus.) | Follows default behavior of element |
zero - tabindex="0" | yes | In tab order relative to element's position in document |
Positive - tabindex="X" (where X is a positive integer between 1 and 32768) | yes | Tabindex value directly specifies where this element is positioned in the tab order. |
Negative - tabindex="-1" | yes | No, author must focus it with element.focus() as a result of arrow or other key press |
Setting a tabindex value of -1 to an element enables the element to receive focus via JavaScript using the element.focus() method. This method is used to enable arrow key navigation to elements. Each element that can be navigated to via arrow keys must have a tabindex of -1 to enable it to receive focus. Here are just a few additional tips to help you with managing keyboard focus:
window.setTimeout(function () { focusItem.focus(); },0); // focusItem must be in scope
<span tabindex="-1" onkeydown="return handleKeyDown();">
If handleKeyDown() returns false, the event will be consumed, preventing the browser from performing any action based on the keystroke.
Use key event handlers to enable activation of the element - For every mouse event handler, a keyboard event handler is required. For example, if you have an onclick="doSomething()" you may also need onkeydown="return event.keyCode != 13 || doSomething();" in order to allow the Enter key to activate that element.
aria-activedescendant property. In addition to tabindex, ARIA provides the aria-activedescendant property for managing the focus of child elements within a widget. Widgets like grid and tree typically manage their children. The root element of the widget should have a tabindex value greater than or equal to "0" to ensure that the widget is in the document tabbing order. Rather than setting a key event handler on each element within a larger component, the event handler can be set on the parent element such as the tree. It is then the job of the parent element to manage the focus of the children.
The parent may use the aria-activedescendant property to indicate the active child. For example, the container element with the role of tree can provide an onkeydown event handler so that each individual tree item within the tree does not need to be focusable and to listen for the keydown event. The container object, in this case the tree, needs to maintain the point of regard and manage which individual child item must be perceived as active.
Important: For a given container widget where activedescendant must cause focus events to be fired to ATs, the actual focus must be on the container widget itself. In HTML this is done by putting tabindex="0" on the container widget.
The key handler on the parent captures the keystrokes and determines what item becomes active next and updates the aria-activedescendant property with the ID of the appropriate, next active child element. The browser takes that ID information and generates the focus event to the assistive technology. Each individual element does not have to be made focusable via a tabindex value of -1, but it must be styled using CSS to indicate the active status
An alternative to using activedescendant is to have the parent element, in response to the same keyboard input, move focus to its children by first removing tabindex from children that do not have focus, which removes them from the tab order. This would be followed by setting the tabindex to "-1" on the element that is to receive focus and then using script to set focus on the element to receive focus. As with aria-activedescendant, this omits managed children from the tabbing order. It enables browsers that do not yet support aria-activedescendant to maintain keyboard navigation, and it provides notification to many assistive technologies like screen magnifiers to move visual focus without relying on other ARIA properties. Today, this technique will work in most user agents, but in the long run aria-activedescendant will require less work by the developer.
Although not always ideal based on the widget you are creating, one benefit of using tabindex to manage focus on an element is that the user agent will scroll the element into view when focus is set to the it. This is not the case for aria-activedescendant. When setting or updating the aria-activedescendant property, e.g. aria-activedescendant="cell23", authors must ensure that the element with id="cell23" is in view. In either case, consider positioning your widget in the visible area of your browser to maximize usability. This can be achieved using available JavaScript scrolling functions.
In some browsers, a JavaScript call to scrollIntoView() on this element should suffice, but in browsers, where this is unreliable, authors should explicitly set the scrollTop and scrollLeft properties of the "cell23" element and its ancestors to scroll the element into view. scrollTop and scrollLeft adjust the node positions by the amounts(pixels) needed to scroll a node into view. Scrolling values are adjusted by the amounts(pixels) needed
to scroll a node into view. This is done by comparing the sizes of the nodes
using available measurements such as scroll+offset+clientWidth/Height/Left/Top. It's important to note that you have to adjust a node so that its viewable within
the context of its parent node. Then you have to move up the DOM tree and make
each parent node visible.
An example of how to handle this can be found in the Dojo Dijit library. Dojo explicitly calls its own implementation of scrollIntoView,dijit.scrollIntoView, at various times, including coincidence with the setting of the aria-activedescendant property. This implementation of scrollIntoView takes a DOM node argument, say "n". Here is the high level algorithm:
dijit.scrollIntoView implements a minimum-position-change algorithm.
Understanding how the DOM scrollIntoView works across browsers is important. Browsers (including Firefox3) force the node either to the top or the bottom of the screen (as defined by the single Boolean parameter) even if its already in view. This is problematic when you only need to scroll horizontally to see the element. It is also problematic when the node is partially off the bottom of the screen and the parameter is (true) which forces the node all the way to the top, and vice versa with the top going to the bottom on (false). IE forces the node to the left of the client area (or right in right-to-left mode) even if it's horizontally in view already.
ThescrollTop and scrollLeft functions create some challenges. scrollTop is always accurate but misleading with respect to inner (nested) scrollbars. scrollLeft cannot be relied on in right-to-left languages because it is sometimes negative and sometimes positive especially with respect to inner (nested) scrollbars. Different browsers handle right-to-left completely differently.
Author-defined keyboard short-cuts or mnemonics present a high risk for assistive technology users. Because they are device-, browser-, and AT-dependent, conflicts among key bindings are highly probable. Therefore, if you needed to use accesskey, you should be aware that it will behave differently in
different browsers. It also may not work with small devices so it is still advisable to ensure that all features are accessible with the basic keys like Tab/shift+tab, arrow, Enter, space and Escape.
The XHTML 2 Working Group is currently developing a new Access Module to address this issue and we hope to have it or a feature like in future versions of (X)HTML. Refer to Section 9: Implementation Guidance.
A tooltip is a popup messages typically triggered by moving a mouse over a control or widget causing a small popup window to appear with additional information about the control. To provide simple text tooltips, the HTML title attribute should more than suffice because the user agent will render it for tooltips. When creating a tooltip, it is essential that the user be able to activate it using the keyboard. When a form control or widget receives keyboard focus, the tooltip must display. When the form control or widget loses focus, the tooltip must disappear. Browsers do not currently support this functionality.
The following code snippet from the iCITA site shows the use of a onfocus="tooltipShow() function to display the tooltip when focus is placed on an element.
<html lang="en-us">
<head>
<title>inline: Tooltip Example 1</title>
<link rel="stylesheet" href="css/tooltip1_inline.css" type="text/css">
<script type="text/javascript" src="js/tooltip1_inline.js"></script>
<script type="text/javascript" src="../js/widgets_inline.js"></script>
<script type="text/javascript" src="../js/globals.js"></script>
<link rel="icon" href="http://www.cites.uiuc.edu/favicon.ico" type="image/x-icon">
<link rel="shortcut icon" href="http://www.cites.uiuc.edu/favicon.ico" type="image/x-icon">
</head>
...
<body onload="initApp()">
<div id="container">
<h1>Tooltip Example 1</h1>
<h2>Create Account</h2>
<div class="text">
<label for="first">First Name:</label>
<input type="text" id="first" name="first" size="20""
onmouseover="tooltipShow(event, this, 'tp1')"
onfocus="tooltipShow(event, this, 'tp1');"
aria-describedby="tp1"
aria-required="false"/>
<div id="tp1" role="tooltip" aria-hidden="true">Your first name is a optional </div>
</div>
...
This section takes a broader look at the Web page. It is intended to assist you in conveying a logical, usable, and accessible layout to an assistive technology or adaptive system designed to modify the visual layout to meet the users needs.
One of the deficiencies of (X)HTML for disabled users has been the usability of keyboard navigation. Users dependent on a keyboard for navigation have been forced to tab everywhere in the document, as the only keyboard accessible document elements are form and anchor elements. This has forced developers to make most everything a link to make it keyboard accessible, and to get to each link you have to tab to it. With the advent of portals and other content aggregation means Web pages are divided into visible regions and there has been no vehicle to get to them other than perhaps to do things such as:
<H1> tag There are number of problems with this approach:
<H1> to mark your regions, this is not consistent across Web sites This remainder of this section provides the author with a playbook for using WAI-ARIA to add semantically rich navigation structure in a Web page so that an assistive technology may provide an effective user experience and avoid these shortcomings.
Follow these steps to assign to mark each logical section:
Identify the logical structure of your page
Break up your page into perceivable block areas which contain semantically associated information called "regions". You can further breakdown each region into logical regions as needed. This is a common process undertaken by portal developers who break the page into perceivable regions called portlets. Think about the user wanting to navigate to these logical block areas on your Web page. Write down a description of what you believe each region to be.
Depending on your Web application you may then need to break it into sub regions depending on the complexity of your Web application. This is a recursive process. A user will look at these perceivable areas like pealing an onion. You might have an outermost collection of perceivable regions or block areas and upon entering each region you may have a collection of regions within it.
Implement the logical structure in markup
Implementing the block structure in markup often involves wrapping elements contained with a "region" such as a <div> or <iframe> with visible borders so that each region or block is perceivable to the user.
Once you have broken up each region you need to label it. The start of each region must have a perceivable header and it should be used to label the region. For details on how to do this see section 3.4.3.1 Header Levels vs. nesting level to create a header to label each region. If you're finding it difficult to come up with a label for the region, make sure at least to use one of the standard roles defined in the following step. The drawback of not providing a label is that users will not know the purpose of the region. By definition, regions would be included in a summary of a page. If an assistive technology were to summarize it would be unable to provide information about the section without a label.
Assign landmark roles to each region
Now that you labeled your regions, you need to assign them semantic navigation landmarks. Landmarks are a vast improvement over the rudimentary "skip to main content" technique employed prior to WAI-ARIA. If possible it is best to use these as landmarks. Skip to main content links impact the layout of applications and only address one main content area. WAI-ARIA provides a collection of landmarks which are applied to each of the regions you identified in step 2.
The presence of common, semantic, navigation landmarks allows each site to support the same standard and allows your assistive technology to provide a consistent navigation experience - an important feature for screen readers and alternate input solutions. For users with cognitive and learning disabilities the landmark information could be used to expand and collapse these regions of your page to aid in simplifying the user experience by allowing the user to manage the amount of information processed at any one time.
There are also mainstream benefits of providing navigation landmarks. Your browser may assign key sequences to move focus to these sections as they can be set on every site. Navigation to these landmarks is device independent. A personal digital assistant (PDA) could assign a device key to get to them in your document. The common landmarks in WAI-ARIA include:
applicationIf the entire web page has a role of application then it should not be treated as a navigational landmark by an assistive technology.
banner complementary contentinfo main navigation search logstatusTo set the landmark in your page:
<div role="log" title="chat log"> <div role="region" title="Game Statistics">
If you have a regional landmark of type application and static descriptive text is available, then on the application landmark, include an aria-describedby reference to associate the application and the static text as shown here:
<div role="applicaton" aria-labelledby="calendar" aria-describedby="info"> <h1 id="calendar">Calendar<h1> <p id="info"> This calendar shows the game schedule for the Boston Red Sox. </p> <div role="grid"> .... </div>
You can create custom regional landmarks by using a generic region. While it is not essential to label these specialized regions with a header, you should provide a title to ensure that the region name is accessible to all users, just as you would the standard regional landmarks. See Header levels versus Nesting levels for directions on how to label the region.
<div role="main"> ... <div role="complementary" title="weather">
Note: the region role is generic and should only be used when a more specific role is not applicable. Assistive technologies should treat this role as a a complementary region.
Indicate to the assistive technology who controls the keyboard navigation
Today's screen readers for the blind have been designed to give the user a "browsing" experience meaning the screen reader consumes a number of keys to aid in the browsing experience. For example, the "up" and "down" arrow keys are used to read the next and previous line of text on your Web page. Accessible rich internet applications will use these keys in an application to navigate within "widgets" like a Tree View.
Assistive technologies must be able to identify widgets which implement WAI-ARIA and allow them use of the keyboard. However, if you have used used numerous widgets to form an application you must set the role on the encompassing region to application. Should you have regions which should be browsed as documents within the application region you should mark those regions with a document role as needed. See section 3.4.2 Structural Roles used to facilitate assistive technology navigation.
When viewing Web content however, screen readers often gather information about all the widgets in an area and present them in a document-like view which the user navigates using keyboard commands provided and controlled by the screen reader. Think of this mode as a virtual environment that presents Web content in a way that makes it convenient for adaptive technology users to navigate and read. This is sometimes called browse mode, or virtual mode. We refer to this as "document browse mode."
Because many screen readers provide document mode navigation support using single key mnemonics on the alpha-numeric keyboard, they may provide a third mode, called "forms mode," used to interact with form controls that are encountered in document mode. Behavior in forms mode is similar to that of application mode. The key feature of forms mode is that it can be toggled with document mode to make it easy to both interact with a specific widget, and read virtualized content of which the widget is a part. Since, as described above, a screen reader's perception of an area as either a document or an application greatly influences how the user reads and interacts with it, ARIA provides content authors a way to indicate whether their pages must be viewed as applications or documents by assistive technologies.
To set document or application mode follow these steps:
After you have divided your Web page into regions through the use of role landmarks and custom regions, you must make a decision: Is your Web page an application or not? If it is, set the role of application on the body tag as follows:
<body role="application">
When using application, all static text must be associated with widgets, groups or panes via using the aria-labelledby and aria-describedby properties, otherwise it will not be read by the screen reader when the user navigates to the related widget or group.
Special Considerations:
application. WAI-ARIA provides dialog and alertdialog roles that are to be treated as special case application roles. Like application, screen readers will leave the main job of keyboard navigation up the application.
When using dialog, all static text must be associated with widgets, groups or panes via using the aria-labelledby and aria-describedby properties, otherwise it will not be read by the screen reader when the user navigates to the related widget or group. Unlike an application, your Web page is unlikely to start out as either of these two roles but rather the author is most likely to dynamically create dialogs or alertdialog sections within the Web page.
Unlike dialog, descriptive text of the alert does not need to be associated via a relationship, as the contents of alert dialogs will be read automatically by the screen reader when the dialog opens.
The default mode for a screen reader to be processing an HTML Web page is document browse mode. This is equivalent to having a role of document on the HTML
<body>tag. If you have already specified a role of application on the body tag there may be times in which you tell the screen reader to switch into "document browse mode" and start stealing the necessary keys to browse a document section of your Web page. These keys are the typical keys used by WAI-ARIA widgets and to provide this level of navigation the keys must be stolen from your browser.To mark areas of your page to tell the assistive technology when to switch into document browse mode, look at the regions/landmarks you have defined and determine which ones must be browsed as a document or navigated as an application. For each region which must be browsed in document browse mode, embed a div element within it with the role of
documentas follows:<div role="document">Now, when a screen reader encounters this region, it will change its interaction model to that of document browsing mode.
This section discusses the use of the heading role and nesting levels.
The heading role value signifies a heading for a section of the document instance. Use of the heading role indicates that a specific object serves as a header. The region of the document to which the heading pertains to should be marked with the aria-labelledby property containing the value of the id for the header.. If you have a heading and there is no element containing the content that it heads, wrap the content in a <div> bearing this aria-labelledby attribute. If headings are organized into a logical outline, the aria-level property can be used to indicate the nesting level. Here is an example:
<p role="main" aria-labelledby="hdr1">
<div role="header" id="hdr1">
Top News Stories
</div>
</p>
Assistive technology briefs users on the context where they are. When they arrive at a new page, a page summary may be given. When they move into a new context, some of the labeling from elements containing the new focus or reading location may be rendered by the assistive technology, to give context to the details to be read next.
The syntactic structure of a page provides the default nesting of contexts. If a paragraph is nested in a <div> or table cell, it is assumed that labels for the <div> or headers for the table cell are pertinent to what is in the paragraph. On the other hand, it is not possible to always flow the logical structure one-to-one into the parse structure.
The aria-owns relationship is provided to annotate logical nesting where the logical child is not a syntactic descendant of the logical parent. In a Rich Internet Application, updates may be made to the document without updating the logical syntactic structure, yet elements may appear to be added to the document structure. From a DOM and accessibility hierarchy perspective aria-owns is a fallback mechanism to using the tree hierarchy provided in the DOM. An example of where aria-owns is needed is a treeitem children where, children in a folder subtree are added to a visible subtree but not be reflected in the actual document subtree of the folder. The aria-owns relationship can be used to associate the folder with new "adopted" child. For more details on the use of aria-owns see section 4.2 Owning and Controlling. The aria-owns relationship is used to indicate to a user agent that a menu is an adopting parent of a sub menu. Another use for aria-owns is a hierarchical diagram where the child nodes of the diagram are not be adequately represented using the DOM structure.
There are several WAI-ARIA roles used to indicate a collection of user interface objects, and each has a distinct purpose:
directory groupregionThe use of each is described below.
The ARIA role, directory, allows authors to mark static table of content sections of a document. Prior to ARIA, the user would need to guess if an area of a document actually pertained to the table of contents. Authors should mark these sections within a document with a role of directory.
<div role="directory">
<ul>
<li>Global Warming Causes
<ul>
<li>CO2 Buildup</li>
<li>Auto emissions<li>
<li>Factory emissions</li>
<li>Destruction of rainforests</li>
</ul>
</li>
<li>Tailoring CO2 buildup</li>
<ul>
<li>Elimination of the incandescent light bulb</li>
<li>Hydrogen fuel cells</li>
<li>Solar energy</li>
<li>Wind power</li>
</ul>
</li>
</ul>
</div>
The presentation role's intended use is to mark an element used to change the look of the page, such as a table that is used to control layout but that does not have all the functional, interactive, or structural relevance implied by the element type for which the presentation role is defined. A presentation element does not need to be mapped to the accessibility API, although it remains in the DOM tree.
A user agent may remove all structural aspects of the element being repurposed. For example, a table marked as presentation would remove the table, td, th, tr and any other child elements of table, while preserving the individual text elements within it. Because the user agent knows to ignore the structural aspects implied in a table, no harm is done by using a table for layout.
The following is an example for using the ARIA presentation role to convey layout:
<table role="presentation">
<tr>
<td>see</td>
<td>spot</td>
<td>run</td>
</tr>
<tr>
<td>over</td>
<td>the</td>
<td>lazy coder</td>
</tr>
</table>
All descendants of the element having a presentation role are still exposed, with the exception of table rows and cells on a table. So, if you were to have forms, images, and text within a table and the table had a role of presentation these elements would be exposed.
Authors should use a role of group to form logical collections of items with related functionality in a widget. A group should not be considered a major perceivable section on a page. A group neither has a heading nor appears in the "Table of Contents." A group may delineate a set of treeitems having the same level in the tree or it may be used to group a set of related checkboxes in a form. Other examples include:
row in a grid; group of children in a tree widget forming a collection of siblings in a hierarchy; or group of items having the same container in a directory Proper handling of a group by assistive technologies, therefore, is determined by the context in which it is provided. Group members that are outside the DOM subtree of the group need to have explicit relationships assigned for them in order to participate in the group. Groups may also be nested.
If an author believes that a section is significant enough in terms of the entire document instance, then the author must assign the section a role of region or one of the designated standard XHTML Role landmark. The designated landmark roles are listed in the section Regions and XHTML Role landmarks..
When defining a region for a section of a document, authors must consider using standard document landmark roles defined by the XHTML Roles Module. This makes it possible for user agents and assistive technologies to treat roles as standard navigation landmarks. If the definition of these regions is inadequate, authors must use the ARIA region role and provide the appropriate title text.
For more information on the use of region see Regions and XHTML Role landmarks.
There are a number of structural roles which are used to support tabular widgets grid and treegrid which indicate additional keyboard navigation as well as the ability to select rows and/or columns. Typically, you would apply these roles to an underlying table in the base markup as shown here:
<table role="grid">
However, in some instances that may not work for the developer, such as when the developer has need for a <div> or <span>, or additional semantics may be needed. To assist, the following roles are provided to support tabular widgets:
When constructing a gridor treegrid the author must use gridcell's for the actual cells:
<table role="grid">
<tr>
<td role= "columnheader">Apples</td><td role= "columnheader">Oranges</td>
</tr>
<tr>
<td role="gridcell">Macintosh</td><td role="gridcell">Valencia</td>
</tr>
</table>
Gridcells are focusable within a grid unlike a table. They may also be editable as is shown in the above example.
Treegrid's may require expanding and collapsing rows which may not be performed using a <tr>. In these instances authors will use an HTML <div>. WAI-ARIA provides a role of row which may be assigned to the <div> to convey to the assistive technology that this is still a row. If you decide to not use the native HTML <table> elements and choose more flexible elements, such as <div> and <span>s, with applied WAI-ARIA roles in this section, you should structurally lay out your elements in line with what you would expect from HTML. All of your rowheaders should be in a row and your gridcells should be children of each subsequent row in the same format as HTML for <td>s and <th>s within <tr>s.
A new feature of WAI-ARIA is the ability to associate descriptive text with a section, drawing, form element, picture, and so on using the aria-describedby property. This is unlike longdesc which typically required the author to create a separate file to describe a picture when it was preferred to have the descriptive text in prose as well so that it was readily available to all users.
<img src="foo" alt="" aria-describedby="prose1"> <div id="prose1"> This prose in this div describes in detail the image foo. </div>
This is the preferred vehicle for providing long descriptions for elements in your document.
In order to be synchronized with the XHTML Role Attribute module, WAI-ARIA includes two XHTML roles which are neither landmarks or widgets of any kind. These roles were incorporated to replace standard elements found in host languages. These roles are definition and note. If either role has a corresponding element in the host language it recommended that authors use the corresponding element in the host language.
The definition role indicates a definition statement in your document.For HTML developers implementing lists of definitions, we recommend you using the DL, DT, and DD elements rather than marking an arbitrary element with a role of definition. An arbitrary element would be appropriate for inline definitions used in conjunction with the DFN element.
Example of an inline definition with an explicit labelledby relationship:
<p>The doctor explained it had been a <dfn id="placebo">placebo</dfn>, or <span role="definition" aria-labelledby"placebo"> or an inert preparation prescribed more for the mental relief of the patient than for its actual effect on a disorder.</span> </p>
Example inline definition with an implicit labelledby relationship determined by nesting:
<p>The doctor explained it had been a <span role="definition"> <dfn>placebo</dfn>, an inert preparation prescribed more for the mental relief of the patient than for its actual effect on a disorder.</span> </p>
Note: In the case where host language semantics do not allow for implicit nesting of definitions terms inside definition roles, authors should explicitly use the aria-labelledby attribute, even when the definition term is nested in the definition as shown here:
<p>The doctor explained it had been a <span role="definition" aria-labelledby="placebo"> <dfn id="placebo">placebo</dfn>, an inert preparation prescribed more for the mental relief of the patient than for its actual effect on a disorder.</span> </p>
The following is an example using a definition list:
<dl> <dt id="anathema">anthema</dt> <dd role="definition" aria-labelledby="anathema">a ban or curse solemnly pronounced by ecclesiastical authority and accompanied by excommunication</dd> <dd role="definition" aria-labelledby="anathema">a vigorous denunciation : cursor</dd> <dt id="homily>homily</dt> <dd role="definition" aria-labelledby="homily">a usually short sermon</dd> <dd role="definition" aria-labelledby="homily">a lecture or discourse on or of a moral theme</dd> </dl>
The note role defines a parenthetic or ancillary remark to the main content of the resource. It also allows assistive technologies to skip over this section of the document unless more information is requested about the main content.
<div role="main" aria-labelledby="foo"> <h1 id="foo">Wild fires spread across the San Diego Hills</h1> Strong winds expand fires ignited by high temperatures ... </div> <div role="note"> This article was last updated July 30, 2008 at 6:05PM. </div>
Marked up content or widgets will often need additional context to make clear what the meaning or purpose is. It is also reasonable that some content media types will need additional descriptions in another format to give clarity to those who are unable to consume the origin format. These additional meta-content sections are linked together by tagging them as labels or descriptions. ARIA provides the aria-labelledby and aria-describedby attributes to signal the browser to feed these relationships into the accessibility layer. This layer is then used by screen readers and other accessibility technology (AT) to gain awareness of how disparate regions are actually contextually connected to each other. With this awareness the AT can then present a meaningful navigation model for discovery and presentation of these additional content sections. The user agent itself can also choose to present these insights in a meaningful way. Generally you should always add these attributes to any widgets on your site as they are often merely a construct of HTML and JavaScript which provides no obvious insight as to what the widget's behavior or interactivity is.
aria-labelledby by attribute. A label should provide the user with the essence of what the object does. For example, you could have a dialog box erected from HTML <div> and you need to assocate a label for the dialog. With a WAI-ARIA role of dialog, you can indicate its widget type and define a label using an HTML header and then associate that label with the dialog using the aria-labelledby relationship.
<div role="dialog" aria-labelledby="dialogheader"> <h2 id="dialogheader">Choose a File</h2> ... Dialog contents >/div<
The section doing the labeling might be referenced by multiple widgets or objects as these need only reference the same id, so contextual description may not always be viable. The labelledby attribute can have multiple ids specified as a space separated list much like applying multiple classes to a single DOM object.
It should be noted that (X)HTML provides a <label for> element which you can use to label form controls. For all visual objects, including (X)HTML form elements, you should use the WAI-ARIA aria-labelledby property for labeling.
Some elements receive their label for embedded text content, but that is the exception.
When one element describes another, use the aria-describedby attribute. An aria-describedby section provides further information about a given object or widget, which may not be intuitively obvious from the context, content or other attributes. For example, a fake window is a common widget used in Web applications and is often constructed using a div absolute positioned in a layer above other content. To simulate common window behavior look and feel there is often an X box in the corner which, when activated, dismisses the window widget. One common way to make this X box is to simply make a link whose content is an X. This doesn't give a non-visual user much to go on and belies the real purpose of the X link. To help we add more descriptive text stored elsewhere in the page like this:
<a role="button" aria-describedby="winClose" href="#" onclick="fakewin.close()">X</a>and then elsewhere in the HTML
<div id="winClose">Closing this window will discard any information entered and return you back to the main page</div>Like labelledby, describedby can accept multiple ids to point to other regions of the page using a space separated list. It is also limited to ids for defining these sets. In our contrived example we would also want a good labelledby section to fully explain what the window does and how closing will effect the task being worked on. If an object or widget lacks describedby the user agent or AT may try to extract information from the label or th tags, if present. The label and th tags have limited use in that they can only be applied to forms or tables, respectively.
ARIA also defines the tooltip role to which aria-describedby may reference an author defined tooltip. The assistive technology can tell from the type of object describing the document element what the purpose of that element is. For example, a screen reader could announce the tooltip without the user having to waive the mouse over the element by following the describedby relationship to a document area with a tooltip role. The aria-describedby property is also useful for describing groups.
Here is a code snippet showing a set of the tooltip:
...
<div class="text">
<label for="first">First Name:</label>
<input type="text"
id="first"
name="first"
size="20"
onfocus="tooltipShow(tooltip1)"
onblur="tooltipHide(tooltip1)"
onmouseover="tooltipShow(tooltip1)"
onmouseout="tooltipHide(tooltip1)"
aria-describedby="tp1"
/>
<div id="tp1" class="tooltip" role="tooltip">Your first name is optional</div>
</div>
...
Two relationships expand the logical structure of a WAI-ARIA Web application. These are aria-owns and aria-controls . The aria-owns relationship completes the parent/child relationship when it cannot be completely determined from the DOM created from the parsing of the markup. The aria-controls relationship defines a cause-and-effect relationship so that assistive technologies may navigate to content effected by and changes to the content where the user is operating.
In addition to WAI-ARIA role and state information, for a document element,
an assistive technology needs to convey its context. In
the case of a treeitem, it is important to know the parent (container),
which may provide a folder depth and the number of siblings in the folder. This containment hierarchy can often be determined by
the DOM tree, as it provides parent, siblings, and children for a given
document element. That said, the DOM hierarchy is rigid and acyclical in
that each node may only have one parent. In some situations, a child
is reused by multiple parents or a child is separated from its
sibilings or parent in the DOM tree. One example is when a radio button
appears in a table but it is not a DOM child of the radiogroup, due to the
authors use of a table for formatting and the placement of the radio buttons
placing them outside the radiogroup container. To solve this problem
WAI-ARIA provides the aria-owns property.
The aria-owns property is set on a document element, and its values are the
unique IDs of all the adopted children. These elements may appear anywhere
in the DOM, yet they are treated as siblings of each owning parent. This
example illustrates a radiogroup that first uses the DOM hierarchy to
convey context and then aria-owns:
First, consider the preferred method for using the W3C DOM to describe the relationship between
radiogroup and radio roles for HTML:
<div id="radio_label">My radio label</div> <ul role="radiogroup" aria-labelledby="radio_label"> <li role="radio">Item #1</li> <li role="radio">Item #2</li> <li role="radio">Item #3</li> </ul>
In this example, the elements with role="radio" are child nodes of the parent role="radiogroup" element node.
Now, consider an alternative method using the aria-owns property to describe the parent-child
role relationship between radiogroup and radio roles for HTML:
<table> <tr> <td role="radiogroup" aria-owns="myradio1 myradio2 myradio3" rowspan="3" > My Radio Label </td> <td id="myradio1" role="radio">Item #1</td> </tr> <tr> <td id="myradio2" role="radio">Item #2</td> </tr> <tr> <td id="myradio3" role="radio">Item #3</td> </tr> </table>
The aria-owns property should be used sparingly, since it
increases the computational load on assistive technology to provide
alternative renderings. Also, when accessing the DOM and enumerating
children of a DOM node, an AT should then enumerate the adopted children
using the aria-owns property. At that instance of walking the DOM, the
parent of the adopted children is the adopted parent and not the DOM
parent. This will avoid recursion problems.
Each child, adopted or natural, should each have the appropriate
aria-posinset and aria-setsize properties set consistent with their
rendering, if these cannot be determined from the DOM from a direct parsing of
the host language. Places where direct parsing does not allow the user
agent to determine
aria-posinset and aria-setsize are long lists where only
the currently visible items are loaded (via Ajax). If the children are
re-sorted then the
aria-posinset and aria-setsize values should be updated
consistent with their visual rendering.
Platform accessibility API mappings must invert this relationship for
assistive technologies, so that they may determine the owning parent from a
child and couple it with
aria-posinset and aria-setsize information to
provide context information to the user.
If you are re-using content across different, transient sections of content by restyling it to render it in association with a different object, you need to maintain the aria-owns property as well to match the current use and apparent ancestry of the reused sub-section. A good example of this is a context help menu that resides at the end of the document. When the user wishes to launch the context help menu in association with different visual elements, styling is used to render the menu in context with that object. Prior to rendering the visual submenu you should ensure the object to which you have requested help assigns its aria-owns property value to the submenu ID. When the menu closes you can remove the aria-owns property.
In rich internet applications document elements may control the behavior on another part of Web page outside themselves. The aria-controls attribute indicates cause-and-effect relationships between document elements.
An example might be a group of radio buttons that "control" contents of a listbox in another part of the page. Here, you would want the radio group to assign a aria-controls relationship to the listbox which will be updating without a page reload. The user, through their assistive technology can then navigate to the listbox by following the aria-controls relationship, when a different radio is selected, to see how the contents changed in the listbox. The ability to update parts of a page without a page reload is a common practice of applications making use of Ajax. Without the aria-controls attribute, a user would be unable to effectively use these types of Web pages as assistive technologies often will not make the user aware of what is happening outside the context of the element the user is currently operating.
With the aria-controls attribute the user may use the assistive technology to follow the relationship to the object it is controlling. It is extremely important for an assistive technology to present changes in the document in response to user input. Therefore, an assistive technology immediately present changes to a live region when the controlling widget is the one which has user keyboard focus. For example, if a tree view controls a help document pane, each time
the tree item changes the new tree item and then the new help contents should also be read. In the case of a screen reader, the amount of information read in the target live region is dependent on how the live region is configured.
The aria-controls attribute takes one or more ids which refer to the document element. If this relationship is not implied by the host language semantics, then the controlling element must be given a controls attribute with the IDs of the other elements where the changes will show up listed in the attribute value.
(X)HTML suffers from a number of disadvantages in keyboard navigation today. One such example is the restriction of navigation to the tabbing order. This is a common problem with presentations in office suites where the logical, perceivable, navigation order of a slide may not match the tabbing order. Sighted users may see a logical navigation process (such as visual steps in the process for assembling a lawn mower). This "flow" is not conveyed by the tab order. The user might tab from step 1 and land on step 4. Another problem is the construction of model-based authoring tools on a Web page. In a model-based authoring tool, a visual object may provide a number of paths that the user can take, such as a multiplexor, which may have output that logically flows to a number of optional electronic components in a drawing. In Web 2.0, developers are actually creating drawings like this to perform tasks such as visually model a work flow. In this scenario, the user will want to decide which object they will navigate their screen reader or alternate input device to next.
Although it is recommended that Tab order follow the reading flow, there may be instances where this is not possible. For these reasons, ARIA provides a relationship property, called aria-flowto. This allows the author to provide an assistive technology with alternative navigation flows through the document that best represents the author's intent and which is more logical for people with disabilities. aria-flowto establishes the recommended reading order of content, so that the an assistive may overriding the default of reading in document order to its user. aria-flowto does not change the keyboard navigation order of they browser.
Consider the first case of changing a basic reading flow to circumvent(X)HTML tabbing. A good example of this is a logical reading flow in a portal with landmarks. In the future, the user may wish to change the reading flow based on the order of priority with which they navigate a personalized Web application like MySpace or MyYahoo. In the following example, the navigation would follow the order of "Top News Stories", "television listings", "stock quotes", and "messages from friends" by following (X)HTML document reading order. However, the author or end user may determine that the main content is most important, followed by "stock quotes", "messages from friends", and then "TV listings."
<html> ... <div role="main" title="Top News Stories" id="main" aria-flowto="stock"></div> <div role="complementary" title="television listings" id="tv"></div> <div role="complementary" title="stock quotes" id="stock" aria-flowto="messages"></div> <div role="complementary" title="messages from friends" id="messages" aria-flowto="tv"></div>
The second use case is such that the Web developer may wish to circumvent the flow by branching to multiple paths in the Web page, requiring the assistive technology to present a collection of options where the user could go next. This is important for work flows or business process management applications as shown in this Process Designer Tool. More of these applications are becoming Web based, and a vehicle is required to tell the user how to get through the work flow. The flowto property takes multiple idrefs, allowing the author to define each object the user could flow to. To implement this technique do the following.
Make each object in the work flow accessible
This will require assigning a title or ARIA label for each object and a unique HTML id. Also, if the html element is repurposed assign it an ARIA role.
<html> ... <img src="foo.jpg" id="331" title="What is the Invoice Value?"> <img src="foo.jpg" id="333" title="Finance Manager Approval"> <img src="foo.jpg" id="334" title="Sales Manager Approval"> ...
For each visual object that will flow to one or more other objects assign the flowto property the list of IDs to which it flows.
<html> ... <img src="foo.jpg" id="331" title="What is the Invoice Value?" aria-flowto="333 334"> <img src="foo.jpg" id="333" title="Finance Manager Approval"> <img src="foo.jpg" id="334" title="Sales Manager Approval"> ...
Use tabindex to enable objects to receive focus. Actually setting focus to them may be performed by an assistive technology, such as an alternative input device. This example places each drawing object in document order with respect to the tab sequence.
<img src="foo.jpg" id="331" title="What is the Invoice Value?"
aria-flowto="333 334" tabindex="0">
<img src="foo.jpg" id="333" title="Finance Manager Approval" tabindex="0">
<img src="foo.jpg" id="334" title="Sales Manager Approval" tabindex="0">
...
When an assistive technology encounters "What is the Invoice Value?," it will know to tell the user that they may choose to navigate either to the "Financial Manager Approval" or to the "Sales Manager Approval" object. The options may be provided through a menu for the What is the Invoice Value object by the assistive technology. After a choice is made, then the AT can move focus to the target object; or in the case of a screen reader, it may just move the user to that location in the screen reader's virtual buffer.
Note: ARIA does not specify backward flowto properties for the same reason that we do not have the reverse of relationships like labelledby. The author may incorrectly do the reversal, creating a whole set of new problems. Rather, the task of the reversal relationships may be handled by the user agent through its accessibility API mapping or in the assistive technology itself.
General rules for managing content and displaying information
display property to ARIA hidden state. This is important for assistive technologies who communicate directly with the user agent's DOM versus a platform accessibility API supported by the user agent. You can also tie CSS visibility:hidden or visibility:collapse to the ARIA hidden state but the use of visibility:hidden will effect layout in that content will continue to flow around the hidden area even though the content to be hidden is invisible. If you are refreshing areas asynchronously, then you need to designate live regions. The following sections explain how to implement live regions and when to use roles that are considered "live" sections by default, including alert, status, or log.
Live regions are parts of a Web page that the author expects to change. Examples of live regions include tables with dynamically updated content (sports stats, stock information), logs where new information is being added (chat transcript logs), notification areas (status, alerts), etc.
Live regions enable assistive technologies, such as screen readers, to be informed of updates without losing the users' place in the content. Live region settings provide hints to assistive technologies about how to process updates. Note that the assistive technology is responsible for handling these updates and enabling users to override these hints.
The section on Live Region Properties and how to use them enumerates the details of how to apply live region properties. This process will help rich internet application (RIA) developers to set live region settings that will provide a good user experience for most assistive technology users with little configuration on their part. When applying these live region properties, it is recommended that you conduct user testing. If the AT supports scripting of the response to live regions you may wish to customize the response, such as through a screen reader script for your Web page.
Identify the live regions
Live regions are any region on a page that receives dynamic updates through client-side scripting. Note the regions of your page that will be live.
See if any of the special case live regions meet your needs
WAI-ARIA provides a number of special case live region roles whose live region properties are pre-defined and which you may use. If one of these live region roles meet your needs just apply the specific role to the region of the Web page.
Decide the priority of each live region
When a live region changes, should the user be notified of the change? Notifications could include a sound for a screen reader user. (For simplicity, we will use the case of an audio notification in this discussion.) The shorter the interval between changes and the less important the information, the less likely that the user needs hears every change. A simple example of changes that should not be heard are changes to time; a sound for every second would be very annoying.
If the user should hear the change, should the change be announced immediately, as soon as possible, or only when the user is idle? Announcing a change immediately can be disorienting for users, so that should be done sparingly. Most updates should probably only be announced when the user is idle.
After you have decided the priority for each live region, then decide the live property value:
aria-live="off"aria-live="polite" aria-live="assertive"Decide how much context is needed for each update
When part of a live region changes, how much context is needed to understand the change. Does the user need to hear the entire live region or just the change by itself?
If the user needs to hear the entire live region, then mark the entire live region with aria-atomic="true".
Decide what types of changes are relevant for each live region
Three possible types of changes are: additions, removals, and text. Additions means new nodes are added to the DOM; removals means nodes are removed from the DOM; and text means changes are solely to the textual content. Should the user hear all types of changes or only certain types?
By default, the user will hear additions and text type changes. If you wish to explicitly define the types of changes, you need to set relevant="THE_TYPES_OF_CHANGES". If more than one type of change is relevant, the types are separated by a space. For example, to define additions and removals as relevant but not text, set relevant="additions removals".
One of the most important concepts behind live regions is politeness. Politeness indicates how much priority a live region has. The following politeness values are available for aria-live: off, polite, and assertive.
aria-live="off"aria-live="polite"aria-live="assertive"There are times to suppress AT presentation changes while a region is updating. For that you can use the aria-busy property.
aria-busy="true"To suppress presentation of changes until a region is finished updating or until a number of rapid-fire changes are finished, set aria-busy="true" and then clear the attribute when the region is finished. While it is busy, the AT will track and collate the changes. It will finally speak the changes once the region is no longer busy
When a live region is updated, the update can often be announced on its own and still make sense. For example, if a news headline is added, it would make sense to simply announce the headline. However, sometimes the entire live region must be read in order to give the user enough context to make sense of the update. For example, it would not make sense to only give the current value of a stock without saying the name of the stock. The atomic setting gives assistive technologies a hint about which of these cases an update falls into.
aria-atomic="false"aria-atomic="true"aria-relevant="additions"aria-relevant="removals"aria-relevant="removals" or aria-relevant="all" should be used sparingly. Notification of an assistive technology when content is removed may cause an unwarranted number of changes to be notified to the user. aria-relevant="text"This example shows two live regions. If both regions update simultaneously, liveRegionA should be spoken first because its message has a higher priority than liveRegionB.
<div id="liveRegionA" aria-live="assertive"> </div> <div id="liveRegionB" aria-live="polite> </div>
You may wish to use a special live region role instead of applying live region properties. ARIA contains a number of standard roles which are by default considered "live" sections of your Web page. It is important to know when to use these and when to create a custom live region on your known. Here are some rules of thumb:
alert- You must use thealertrole for a one-time notification which shows for a period of time and goes away and is intended to alert the user that something has happened. The assistive technology should be notified, by the user agent, that an alert has occurred providing your operating system supports this type of event notification. When choosing to use alert you should use thealertdialogrole instead if something inside the alert is to receive focus. Bothalertandalertdialogappear to pop-up to the user to get their attention.
status- You must use thestatusrole when you want to mark an area which is updated periodically and provides general status of your Web application. Changes in status are not typically announced automatically by an assistive technology. However, it is possible to configure some assistive technologies, such as a scriptable screen reader, to watch for changes in the status bar and announce them. Using the status role is also important in that the user could always check the status section for changes in status on different Web pages. Many applications provide status widgets and they are often found, visibly, at the bottom of the application and contain a variety of widgets within it to convey status. The use ofstatusdoes not guarantee how the AT will respond to changes in the status. The author can still put live="off" or live="assertive" to influence the ATs treatment of the status.
timer- You must use a timer role when you want to mark an area which indicates an amount of elapsed time from a start point, or the time remaining until an end point. The text encapsulated within the timer indicate the current measurement, indicate the current time measurement, and are updated as that amount changes. However the timer value is not necessarily machine parsable. The text contents MUST be updated at fixed intervals, except when the timer is paused or reaches an end-point.
marquee- You must use a marquee role when you need to mark an area with scrolling text such as a stock ticker. The latest text of the scrolled area must be available in the DOM. A marquee behaves like a live region, with an assumed defaultaria-liveproperty value of "polite."
log- You must use log if you have a live area where new information is added, like a scrolling chat log of text. Unlike other regions, implied semantics indicate the arrival of new items and the reading order. The log contains a meaningful sequence and new information is added only to the end of the log, not at arbitrary points. If the have a chat text entry area you should indicate that it also controls the aria log aria like so:<div contenteditable="true" role="log" id="chatlog"> </div> <label id="gettext">Send Text</label> <div aria-controls="chatlog" role="textbox" contenteditable="true" aria-labelledby="gettext"> </divlive region - If you have some other live area use case, ARIA allows you to mark an area using the
aria-liveattribute. This accompanied by the collection of attributes which support the live property allow you to create your own custom live area on your Web page. For more details regarding live regions refer to the live region section of the this guide.
This section identifies best practices for elements used as form elements.
Until the introduction of WAI-ARIA's aria-invalid state and aria-required property, only presentational strategies have been available to Web content authors to indicate that certain form fields and controls are required or invalid. In applications, these states are only available through styling or varying markup, which is inconsistent, and therefore is inconclusive. In Web-based forms, fields required may be marked by an asterisk. Forms submitted with required data missing or improperly specified may be redisplayed with the unacceptable elements highlighted in red. The assistive technology user is poorly served by such imprecise methods, and all users confront inconsistent indicators for consistent situations.
The ARIA invalid state and required property provide:
When a text input field that has a maximum length value (or the host markup language's equivalent) receives focus, the value defined for "maximum length" should be communicated to the user. When text entry reaches that maximum length (or the markup language's equivalent), an alert (expressed in accordance with user preferences and capabilities) should inform the user that the maximum length for a given field has been reached. Such an alert can be expressed programmatically or if, using as an aural icon, by using a WAI-ARIA alert; the user agent may alert the user through a system beep and by triggering the operating systems' "show sounds" facility. When maximum length (or the markup language's equivalent) is reached, the user must then be able to move to another form field in a manner consistent with tab-navigation for that document.
Having a user agent automatically change focus in a form in response to user input can be advantageous in situations where that change saves the user keystrokes or on-screen keyboard interaction in order to manually move the focus from one field to another. However, as with form auto-completion, this type of text input event must be firmly under user control because this may not have been the user's intention and some users with disabilities may become disoriented such as those with sight impairments. Consider these cases:
Use caution when using automatic submission of a form without explicit user command or in response to a user-defined setting that permits such behavior, as expressed by the Priority 1 UAAG 1.0 Checkpoints 7.1, 7.2 and 11.1. Unless the user has specifically chosen to set the user agent to allow auto-submission, authors are advised not to set onChange or onFocus events either to trigger submission of a form or to provide an auto-submission event upon completion of all or all required fields of a form or input field.
Drag-and-drop operations are a common feature of Rich Internet Applications (RIAs). Drag-and-drop features have traditionally challenged people with functional disabilities. These problems arise from the difficulty of manipulating the mouse, finding targets capable of receiving the object being dragged, and actually moving the object to the drop target. Screen readers and alternate input systems assist the user to some degree by allowing the user to simulate a click, drag, and release operation. It is then up to the user to find a target that, hopefully, will receive the object(s) being dragged. Additionally, the user may not be aware if the desired drop operation is supported or what source objects can be selected for dragging. The end result can be a very unproductive and frustrating experience.
ARIA introduces two new Drag and Drop properties that aide Web application authors with the drag and drop process, called aria-grabbed and aria-dropeffect. The property aria-grabbed is applied to the source(s) being dragged, while aria-dropeffect is applied to the target(s). Use of these properties--combined with best practices for enabling the user to select the appropriate drag operations and for assigning appropriate keyboard operations for dragging and dropping--will vastly improve the accessibility of drag and drop functionality. The following steps will guide you through the process.
Identify draggable objects
Set the initial aria-grabbed state of all draggable interface objects.
Roles that typically support drag and drop operations are listitem and treeitem. The default state for all objects is assumed to be undefined, meaning that they are not draggable. For objects that may be dragged, set the aria-grabbed state to "false". This will allow assistive technologies to indicate which objects are draggable and potentially facilitate in choosing the objects to grab.
Objects that can be dragged need to have a determinable role. HTML tags such as <div> and <span> provide no semantics, unlike <select>, and would require you to set the WAI ARIA role attribute.
This step clearly marks elements that can be "grabbed" for drag-and-drop operation. Assistive technologies, such as screen readers or alternate input devices, can help the user move focus directly to the grab-supporting objects without having to navigate through all the elements and to guess which could be ready to initiate a drag operation. Although not necessary, authors or intermediaries could use CSS to highlight those elements that may be grabbed. At this point, qualified drop targets cannot be determined as they are determined based on the objects being dragged--which have not yet been selected.
All grabbable objects must be navigable using the keyboard.
Allow the user to initiate the appropriate drag operation using the keyboard
The author must provide a keyboard accessible way of selecting one or
more elements to drag. It is recommended that the space bar be used for
selection. It is further recommended that Shift+Spacebar be used to select
multiple objects and define a contiguous set; and that control+space be
used to define a noncontiguous set. As each object is selected, its
aria-grabbed property must be set to "true", giving the ATs references as
to what has been grabbed. It is recommended that control+m be supported
to indicate that all objects have been selected for drag.
Note: Selection of the objects to be dragged may differ depending on their type. For example, a list of emails that might be selected one at a time or many at a time, either in contiguous or noncontiguous locations, selected be easily with the Space key as indicated above. However, text in a document might better be selected by positioning the cursor at the beginning of a word and holding down the Ctrl key while using the right and left arrow keys to mark the letters you wish to move.
Mark the drop targets
When it is determined that all source objects have been "grabbed", you
must indicate which targets may receive them by setting the aria-dropeffect properties on those targets. This enables an assistive
technology to keep track of the drop targets to
assist the user in navigating to drop targets. The aria-dropeffect property supports one or more of the following values reflecting what
your application will support in the case of a drag-and-drop operation:
Example:
<div role="treeitem" aria-dropeffect="copy move popup">
CSS may also be used to highlight the targets to show sighted users
which objects can receive a drop of the grabbed source(s). Any object
without an aria-dropeffect property set will have an assumed
aria-dropeffect value of "none." Any object with an aria-dropeffect value
of "none" is ignored by ATs in the drop operation.
Implement keyboard functionality to assist the user and AT with executing the drop.
After all objects have been grabbed, the author should provide standard keyboard accessible navigation (such as through tabbing) to enable the user to navigate to the desired drop target. To achieve this, you may optionally support Shift+F10 to invoke a single select list of possible drop targets from which the user may choose a single drop target that, when selected, would move focus to that drop target. Otherwise, you must provide a keyboard accessible way (through tabbing and arrowing) to allow the user to navigate to the drop target. The user's point of regard should be clearly visible during this navigation.
When the user arrives at the drop target the author should provide a keyboard accessible way to drop the selected object(s) onto the target. Control+M should be used to provide the most intuitive type of drop, either copy, move, or a shortcut. In the case of only one drop operation available, the Control+M should be used to drop the selected object(s) onto the target.
If drop target supports additional drop operations, then the
author should provide an ARIA-enabled pop-up menu from which the user
can choose supported operations from the list. A recommended way to
invoke this menu is to use the Shift+Control+M key sequence when focus
is on the drop target. Furthermore, the aria-dropeffect property should include "popup" in its list of values to indicate that a
keyboard accessible menu is provided. After the user has selected an
action from the pop-up menu, the menu must close, with focus returning
to the drop target. If the user does not choose an action and instead
presses the Escape key, the application must dismiss the menu,
returning focus to the drop target.
Cancelling a drag operation
If at any time during the drag process, the user pressed the Escape key to cancel drag operations, all aria-dropeffect properties must be set to "none", keyboard focus should return to the last grabbed source object, and all grabbable objects' aria-grabbed properties must be set to "supported."
Clean-up after drag/drop
Once the drop has occurred, you should clean up the DOM as you would do for drag-and-drop operation. This should include setting:
aria-dropeffect properties to "none" or remove them altogether.aria-grabbed of draggable objects to "false".aria-grabbed property or have an aria-grabbed property set to "undefined."Other methods of performing the same operation as drag-and-drop may be the best way to meet the accessibility requirements. As an example, when moving a mail message from the inbox to another folder, a list of those folders could be presented in a select list as an alternative to drag-and-drop.
Document non-recommended keyboard navigation
If the author must use alternatives to the keyboard navigation recommended here, it should be documented on the page.
States and Properties that an Assistive Technology is likely to change:
Authors should monitor changes to these properties by monitoring <a href="http://www.w3.org/TR/2000/REC-DOM-Level-2-Events-20001113/events.html#Events-MutationEvent">DOM Mutation events</a> for attribute changes and respond accordingly by making the appropriate changes to you web application. Note that if any of these states and properties are set in error, the Web application is responsible for handling the error condition.
The following States and Properties are unlikely to be manipulated by an assistive technology: An AT would need to have greater understanding of the application and the results could be adverse.
For these widgets and structures, this document describes the keyboard interaction and identifies the relevant ARIA roles, states, and properties.
If the host language does not define key mappings, such as hot keys, and the author defines key mappings other than those described here or in Drag-and-Drop Support, then the author must provide documentation of those key mappings in the contents of the web page.
The following may apply to some or all widgets.
Writing rich internet applications is much more difficult than writing in HTML. It is even more work to ensure your application runs in multiple browsers and supports WAI-ARIA. It is highly recommended that you reuse existing rich internet application widget libraries which have implemented WAI-ARIA. The authors of these libraries will have to have gone through:
It is recommended that authors start by using a UI component library which has already implemented WAI-ARIA like the Dojo Toolkit Dijit library.
This section is informative.
This section is informative.
The following people contributed to the development of this document.
Special thanks to Aaron Leventhal for effort and insight as he implemented a working prototype of accessibility API bindings.
Simon Bates, Judy Brewer (W3C/MIT), Christian Cohrs, Becky Gibson (IBM), Alfred S. Gilman, Andres Gonzalez (Adobe), Jeff Grimes (Oracle), Barbara Hartel, Earl Johnson (Sun), Jael Kurz, Linda Mao (Microsoft), Shane McCarron (ApTest), Dave Pawson (RNIB), Henri Sivonen (Mozilla), Vitaly Sourikov, Mike Squillace (IBM), Ryan Williams (Oracle), Tom Wlodkowski.
This publication has been funded in part with Federal funds from the U.S. Department of Education, National Institute on Disability and Rehabilitation Research (NIDRR) under contract number ED05CO0039. The content of this publication does not necessarily reflect the views or policies of the U.S. Department of Education, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.