[contents] _________________________________________________________________ W3C Techniques for User Agent Accessibility Guidelines 1.0 W3C Working Draft 29-October-1999 This version: http://www.w3.org/WAI/UA/WD-WAI-USERAGENT-TECHS-19991029 (plain text, postscript, pdf, gzip tar file of HTML, zip archive of HTML) Latest version: http://www.w3.org/WAI/UA/WAI-USERAGENT-TECHS Previous version: http://www.w3.org/WAI/UA/WAI-USERAGENT-TECHS-19991005 Editors: Jon Gunderson, University of Illinois at Urbana-Champaign Ian Jacobs, W3C Copyright © 1999 W3C® (MIT, INRIA, Keio), All Rights Reserved. W3C liability, trademark, document use and software licensing rules apply. _________________________________________________________________ Abstract This document provides techniques for implementing the checkpoints defined in "User Agent Accessibility Guidelines 1.0". These techniques address the accessibility of user interfaces, content rendering, program interfaces, and languages such as HTML, CSS and SMIL. This document is part of a series of accessibility documents published by the Web Accessibility Initiative. Status of this document This section describes the status of this document at the time of its publication. Other documents may supersede this document. The latest status of this document series is maintained at the W3C. This is a W3C Working Draft for review by W3C Members and other interested parties. It is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress". This is work in progress and does not imply endorsement by, or the consensus of, either W3C or Members of the WAI User Agent (UA) Working Group. While User Agent Accessibility Guidelines 1.0 strives to be a stable document (as a W3C Recommendation), the current document is expected to evolve as technologies change and content developers discover more effective techniques for designing accessible Web sites and pages. Please send comments about this document to the public mailing list: w3c-wai-ua@w3.org. This document has been produced as part of the Web Accessibility Initiative, and is intended as a draft of a Proposed Recommendation for how to improve user agent accessibility. The goals of the WAI UA Working Group are discussed in the WAI UA charter. A list of the UA Working Group participants is available. A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR. Table of Contents * Abstract * Status of this document * 1 Introduction + 1.1 Priorities * 2 User Agent Accessibility Guidelines + 1. Support input and output device-independence + 2. Ensure user access to all content + 3. Allow the user to turn off rendering or behavior that may reduce accessibility + 4. Ensure user control over styles + 5. Observe operating system conventions and standard interfaces + 6. Implement open specifications and their accessibility features + 7. Provide navigation mechanisms + 8. Help orient the user + 9. Notify the user of content and viewport changes + 10. Allow the user to configure the user agent + 11. Provide accessible product documentation and help * 3 Accessibility Topics + 3.1 User control of style + 3.2 Link techniques + 3.3 Table techniques + 3.4 Frame techniques + 3.5 Form techniques + 3.6 Script techniques + 3.7 Abbreviations and acronyms * 4 Appendix: Accessibility features of some operating systems * 5 Appendix: Loading assistive technologies for DOM access * 6 Appendix: Assistive Technology Functionalities * 7 Appendix: Terms and Definitions * 8 Acknowledgments * 9 References * 10 Services _________________________________________________________________ 1 Introduction 1.1 Priorities Each checkpoint in this document is assigned a priority that indicates its importance for users. [Priority 1] This checkpoint must be satisfied by user agents as a native feature, otherwise one or more groups of users with disabilities will find it impossible to access information. Satisfying this checkpoint is a basic requirement for some individuals to be able to use the Web. [Priority 2] This checkpoint should be satisfied by user agents as a native feature, otherwise one or more groups of users will find it difficult to access information. Satisfying this checkpoint will remove significant barriers to accessing Web documents. [Priority 3] This checkpoint may be satisfied by user agents as a native feature to make it easier for one or more groups of users to access information. Satisfying this checkpoint will improve access to the Web for some individuals. _________________________________________________________________ 2 User Agent Accessibility Guidelines This section lists each checkpoint of the Guidelines along with some possible techniques for satisfying it. Each checkpoint also links to larger accessibility topics where appropriate. Guideline 1. Support input and output device-independence 1.1 Ensure that every functionality offered through the user interface is available through every input device APIs implemented by the user agent. User agents are not required to reimplement low-level functionalities (e.g., for character input or pointer motion) that are inherently bound to a particular API and most naturally implemented through that API. [Priority 1] Note. The device-independence required by this checkpoint applies to functionalities described by the other checkpoints in this document unless otherwise stated by individual checkpoints. This checkpoint does not require user agents to support all operating system input device APIs, only to make the software accessible through those they do implement. Techniques: Operating system and application frameworks provide standard mechanisms for controlling application navigation for standard input devices. In the case of Windows, OS/2, the X Windows System, and MacOS, the window manger provides GUI applications with this information through the messaging queue. In the case of non-GUI applications, the compiler run-time libraries provide standard mechanisms for receiving keyboard input in the case of desktop operating systems. Should you use an application framework such as the Microsoft Foundation Classes, the framework used must support the same standard input mechanisms. When implementing custom GUI controls do so using the standard input mechanisms defined above. Examples of not supporting the standard input devices are: + Do not communicate directly with the device. For instance, in Windows, do not open the keyboard device driver directly. This may circumvent system messaging. It is often the case that the windowing system needs to change the form and method for processing standard input mechanisms for proper application coexistence within the user interface framework. + Do not implement your own input queue handler. Devices for mobility access, such as those that support serial keys, use the standard input queue to control applications. __________________________________________________________ 1.2 Implement the standard input and output device APIs of the operating system (e.g., for mouse, keyboard, speech input, etc.) [Priority 1] 1.3 Ensure that the user can interact with all active elements in a device-independent manner. [Priority 1] For example, users who are blind or have motor impairments must be able to activate the links in a client-side image map without a pointing device. One technique for doing so is to render client-side image maps as text links. Note. This checkpoint is an important special case of checkpoint 1.1. Techniques: Refer to checkpoint 1.1 and checkpoint 1.5. For client-side image maps: + If alternative text ("alt" or "title" in HTML) is available and not null for the element (like INPUT or IMG in HTML) that points to a client-side map, then render some text indicating a map (like "Start of map") plus the alternative text and the number of areas in the map. If alt text is null, do not render the map or its areas. + For each AREA in the map, if alternative text ("alt" or "title") is available and not null, then render the alternative text as a link. Otherwise, render some text like "Map area" plus part or all of the href as a link. If alt "text" is null for an AREA, do not render that AREA. + When reading through the whole Web page, read the start of map alternative text with the number of areas, but skip over the AREA links. To read and activate the map areas, use keys that read and navigate link by link or element by element. __________________________________________________________ 1.4 Ensure that every functionality offered through the user interface is available through the standard keyboard API. [Priority 1] Functionalities include being able to show, hide, resize and move graphical viewports created by the user agent. Note. This checkpoint is an important special case of checkpoint 1.1. 1.5 Ensure that all messages to the user (e.g., warnings, errors, etc.) are available through all output device APIs implemented by the user agent. [Priority 1] For instance, ensure that information about how much content has been viewed is available through output device APIs. Proportional navigation bars may provide this information graphically, but the information must be available (e.g., as text) to users relying on synthesized speech or braille output. Techniques: Operating system and application frameworks provide standard mechanisms for using standard output devices. In the case of common desktop operating systems such as Windows, OS/2, and MacOS, standard API are provided for writing to the display and the multimedia subsystems. It is important to also support standard output notification of sound such as notifications found in the Windows control panel for sounds. Windows maps accessibility features to the event caused by generation of these specific system sounds. Accessibility features such as SoundSentry would flash the screen, as appropriate, in response to events that would cause these sounds to play. This enables the users with deafness to use the application in the absence of sound. When implementing standard output, do not: + Render text in the form of bitmap before transferring to the screen. Screen Readers intercept text drawing calls to create a text representation of the screen, called an offscreen model, which is read to the user. Common operating system 2D graphics engines and drawing libraries provide functions for drawing text to the screen. Examples of this are the Graphics Device Interface (GDI) for Windows, Graphics Programming Interface (GPI) for OS/2, and for the X Windows System or Motif it is the X library (XLIB). + Provide your own mechanism for generating pre-defined system sounds. + When using a device do not use the device driver directly. Screen readers are designed to monitor what is drawn on the screen by hooking drawing calls at different points in the of the drawing process. By calling the display driver directly you may be drawing to the display below the point at which a screen reader for the blind is intercepting the drawing call. + Do not draw directly to the video frame buffer. This circumvents the interception point at which a screen reader hooks the display calls. __________________________________________________________ Guideline 2. Ensure user access to all content 2.1 Ensure that the user has access to all content, including alternative representations of content. [Priority 1] Note. Although it is not a requirement that alternative content be available at the same time as primary content, some users may benefit from simultaneous access. For instance, users with low vision may want to view images (even imperfectly) but require alternative text for the image to be rendered in a very large size or as speech. Techniques: It is not sufficient to convert a rendering intended for one medium into a rendering for a different medium (e.g., a graphical rendering to speech) since structural information is lost. Examples: table cells, nested lists (want to know where list item ends). Also, serial access to content not always convenient, so we need additional mechanisms to select and receive content. Where does content come from? Some combination of document source, style sheets (which may hide content or generate content), and user agent additions (which may add contextual information or dynamic information such as whether a link has been visited). In addition, the user agent may want to provide "intelligent" access to content to simplify the view or to convey models more familiar to users than what is conveyed by the DTD alone. In the Amaya browser ([AMAYA]), users may access attribute values as follows: Place the cursor at the element in question, open/swap to the structure view. You are shown list of attributes and values. Another technique: select the element (press escape in Linux), then the attributes are all available from the attributes menu. For alt, one can also look at the alternate view, which renders alt text instead of images - a lynx-like view. All the views are synchronized for navigation (and for editing). What does access mean? Access means that the user agent renders selected content. Content includes text, video, audio, and alternative equivalents to them (which may be attribute values, element content, external resources, etc.). In the simplest case, the user agent renders the document (e.g., two-dimensional graphical layout, audio stream, line-by-line braille stream) and the user has access to the entire rendering. But this is not sufficient and so the user agent must provide navigation mechanisms that allow the user to set the selection/focus and then request the selected content (or information about the content - refer to another section...). User interface issues o How to indicate what piece of content one wants to access? o How does the user agent present the information? o How does the user configure the user agent to present associated contextual information? Refer to the section on navigation for different navigation techniques (serial, direct, tree, etc.). Structured v. Unstructured selection. o Users may want to select content based on the rendering structure alone (i.e., that amounts to selecting across element borders). o Users may want to select content based on structure (e.g., a table cell). Contextual information In addition to providing information about content, user agents should provide contextual information. Examples: table cell row/column position or header information. Or list item number within nested lists. Contextual information includes language of content as well. + Refer to the section on link techniques. + Refer to the section on table techniques. + Refer to the section on frame techniques. + Refer to the section on form techniques. + Refer to the section on abbreviations and acronyms. + To provide text equivalents of non-text content: o Look for the "alt" attribute (e.g., on IMG in HTML). o Look for the "title" attribute o If the replaced content is text (e.g., a "text" element in SMIL), use the text content. + The "Altifier Tool" (refer to [ALTIFIER]) illustrates smart techniques for generating alternative text for images, etc. when the author hasn't supplied any. Speech-based user agents providing accessible solutions for images should, by default, provide no information about images for which the author has provided no alternative text. The reason for this is that the image will clutter the user's view with unusable information adding to the confusion. In the case of an speech rendering, nothing should be spoken for the image element. This user should be able to turn off this option to find out what images were inaccessible so that the content author could be contacted to correct the problem. In the case of videos, an assistive technology should, by default, notify the user that a video exists as this will likely result in the launch of a plug-in. In the case of a video, user agents should indicate what type of video it is, accompanied by any associated alternative equivalent. User agents should prefer plug-ins that support system-specific accessibility features over those that don't. In the case of applets, an assistive technology should, by default, notify the user that an applet exists, as this will likely result in the launch of an associated plug-in or browser specific Java Virtual Machine. In the case of an applet, the notification should include any associated alternative equivalent. This is especially important since applets typically do provide an application frame that would provide application title information. When an applet is loaded, it should support the Java system conventions for loading an assistive technology (refer to the appendix on loading assistive technologies for DOM access). When the applet receives focus, the browser user agent should first notify the user about the applet as described in the previous paragraph and turn control over to the assistive technology that provides access to the Java applet. In [HTML40], alternative content may come from the following sources: + For the IMG element: The "alt", "title", and "longdesc" attributes. + For the OBJECT element: The content of the element and the "title" attribute. + For the APPLET element: The "alt" attribute and the content of the element. + For the AREA element: The "alt" attribute. + For the INPUT element: The "alt" attribute. + For the ACRONYM and ABBR elements: The "title" attribute may be used for the acronym or abbreviation expansion. + For the TABLE element, the "summary" attribute. + For frames, the NOFRAMES element and the "longdesc" attribute on FRAME and IFRAME. + For scripts, the NOSCRIPT element. __________________________________________________________ 2.2 If more than one alternative equivalent is available for content, allow the user to choose from among the alternatives. This includes the choice of viewing no alternatives. [Priority 1] For example, if a multimedia presentation has several closed captions available (e.g., in different languages, different levels of detail, etc.) allow the user to choose from among them. 2.3 Render content according to natural language identification. [Priority 1] Natural language may be identified by markup (e.g., the "lang" attribute in HTML [HTML40] or "xml:lang" in [XML]) or HTTP headers. Refer also to checkpoint 2.9 and checkpoint 5.3. 2.4 Provide time-independent access to time-dependent active elements or allow the user to control the timing of changes. [Priority 1] Techniques: + Provide time-dependent information in a time-independent manner, such as a static list of links that are time-dependent and occupy the same screen real estate. + Allow the user to control the timing of changes. + Allow the user to navigate sequences of related links that vary over time. __________________________________________________________ 2.5 Allow the user to specify that continuous equivalent tracks (e.g., closed captions, auditory descriptions, video of sign language, etc.) be rendered at the same time as audio and video tracks. [Priority 1] 2.6 If a technology allows for more than one audio track, allow the user to choose from among tracks. [Priority 1] 2.7 When no text equivalent has been specified, indicate what type of object is present. [Priority 2] 2.8 When alternative text has been specified explicitly as empty (i.e., an empty string), render nothing. [Priority 3] 2.9 For identified but unsupported natural languages, notify the user of language changes when configured to do so. [Priority 3] Techniques: A user agent should treat content language as part of contextual information. When the language changes, the user agent should either render the content in the supported language or notify the user of the language change (if configured for notification). Rendering could involve speaking in the designated language in the case of an audio browser or screen reader. If the language was not supported, the language change notification could be spoken in the default language by a screen reader or audio browser. Language switching for blocks of content may be more helpful than inline language switching. In some language combinations, less than a few words long foreign phrases are often well-integrated in the primary language (e.g., Japanese being the primary and English being the secondary or quoted). In such situations, dynamic switching in in-line level may make the reading sound unnatural, and possibly harder to be understood. Language information for HTML ("lang", "dir") and XML ("xml:lang") should be made available through the DOM ([DOM1]). User agents may announce language changes using style sheets and generating text (refer to [CSS2]) that indicates the change of language. __________________________________________________________ Guideline 3. Allow the user to turn off rendering or behavior that may reduce accessibility 3.1 Allow the user to turn on and off rendering of background images. [Priority 1] Techniques: + In [CSS1], background images may be turned on/off with the 'background' and 'background-image' properties. __________________________________________________________ 3.2 Allow the user to turn on and off rendering of background audio. [Priority 1] Techniques: + Users sometimes specify background sounds with the "bgsound" attribute. Note. This attribute is not part of [HTML40]. + In [CSS2], background sounds may be turned on/off with the 'play-during', property. __________________________________________________________ 3.3 Allow the user to turn on and off rendering of video. [Priority 1] 3.4 When the user agent renders audio natively, allow the user to turn on and off rendering of audio. [Priority 1] 3.5 Allow the user to turn on and off animated or blinking text. [Priority 1] Techniques: + The BLINK element. Note. The BLINK element is not defined by a W3C specification. + The MARQUEE element. Note. The MARQUEE element is not defined by a W3C specification. + The CSS 'blink' value of the 'text-decoration' property. __________________________________________________________ 3.6 Allow the user to turn on and off animations and blinking images. [Priority 1] 3.7 Allow the user to turn on and off support for scripts and applets. [Priority 1] Note. This is particularly important for scripts that cause the screen to flicker, since people with photosensitive epilepsy can have seizures triggered by flickering or flashing in the 4 to 59 flashes per second (Hertz) range. Users should be able, for security reasons, to prevent scripts from executing on their machines. Techniques: Refer to the section on script techniques __________________________________________________________ 3.8 Allow the user to turn on and off rendering of images. [Priority 3] 3.9 Allow the user to turn on and off author-specified forwards that occur after a time delay and without user intervention. [Priority 3] Techniques: Page refresh according to an author-specified time interval can be achieved with the following markup in HTML: The user agent should allow the user to disable this type of page refresh. Although no HTML specification defines this behavior formally, some user agents support the use of the META element to refresh the current page after a specified number of seconds, with the option of replacing it by a different URI. Instead of this markup, authors should use server-side redirects (with HTTP). User agents can provide a link to another page rather than changing the page automatically. __________________________________________________________ For example, when forwarding has been turned off, offer a static link to the target. 3.10 Allow the user to turn on and off automatic content refresh. [Priority 3] For example, when turned off, allow the user to refresh content manually instead (through the user interface). Guideline 4. Ensure user control over styles Checkpoints for fonts and colors: 4.1 Allow the user to control font family. [Priority 1] 4.2 Allow the user to control the size of text. [Priority 1] For example, allow the user to control font size through style sheets or the user interface. Or allow the user to magnify text. 4.3 Allow the user to control foreground color. [Priority 1] 4.4 Allow the user to control background color. [Priority 1] 4.5 Allow the user to control selection highlighting (e.g., foreground and background color). [Priority 1] 4.6 Allow the user to control focus highlighting (e.g., foreground and background color). [Priority 1] Checkpoints for applets and animations: 4.7 Allow the user to control animation rate. [Priority 2] Checkpoints for video. 4.8 Allow the user to control video frame rates. [Priority 1] 4.9 Allow the user to control the position of audio closed captions. [Priority 1] 4.10 Allow the user to start, stop, pause, and rewind video. [Priority 2] Checkpoints for audio: 4.11 Allow the user to control audio playback rate. [Priority 1] 4.12 When the user agent renders audio natively, allow the user to control the audio volume. [Priority 2] 4.13 Allow the user to start, stop, pause, and rewind audio. [Priority 2] Checkpoints for synthesized speech: 4.14 Allow the user to control synthesized speech playback rate. [Priority 1] 4.15 Allow the user to control synthesized speech volume. [Priority 1] 4.16 Allow the user to control synthesized speech pitch, gender and other articulation characteristics. [Priority 2] Checkpoints for the user interface: 4.17 Allow the user to select from available author, user, and user agent default style sheets. [Priority 1] Note. Users should be able to select no style sheets, effectively turning them off. 4.18 Allow the user to control user agent-initiated spawned viewports. [Priority 2] For example, in HTML, allow the user to control the process of opening a document in a new target frame or a viewport created by author-supplied scripts. In SMIL 1.0, allow the user to control viewports created with show="new". Control may involve prompting the user to confirm or cancel the viewport creation. Users may also want to control the size or position of the viewport and to be able to close the viewport (e.g., with the "back" functionality). Techniques: User agents may: + Allow users to turn off support for spawned viewports entirely + Prompt them before spawning a viewport For example, user agents may recognize the HTML construct target="_blank" and spawn the window according to the user's preference. __________________________________________________________ Guideline 5. Observe operating system conventions and standard interfaces 5.1 Provide accessible APIs to other technologies. [Priority 1] 5.2 Use accessibility resources and conventions of the operating system and supported programming languages, including those for plug-ins and virtual machine environments. [Priority 1] For instance, if the user agent supports Java applets and provides a Java Virtual Machine to run them, the user agent should support the proper loading and operation of a Java native assistive technology. This assistive technology can provide access to the applet as defined by Java accessibility standards. Techniques: The operating system application programming interfaces (APIs) that support accessibility are designed to provide a bridge between the standard user interface supported by the operating system and alternative user interfaces developed by third-party assistive technology vendors to provide access to persons with disabilities. Applications supporting these APIs are therefore generally more compatible with third-party assistive technology. The User Agent Accessibility Guidelines Working Group strongly recommends using and supporting APIs that improve accessibility and compatibility with third-party assistive technology. Third-party assistive technology can use the accessibility information provided by the APIs to provide an alternative user interface for various disabilities. The following is an informative list of currently public APIs that support accessibility: + Microsoft Active Accessibility ([MSAA]) in Windows 95/98/NT versions. + Sun Microsystems Java Accessibility API ([JAVAAPI]) in Java Code. Many operating systems have built-in accessibility features for improving the usability of the standard operating system by persons with disabilities. When designing software that runs above an underlying operating system, developers should ensure that the application: 1. Makes use of operating system level features. See the appendix of accessibility features for some common operating systems. 2. Inherits operating system settings related to accessibility. Pertinent settings include font and color information as well as other pieces of information discussed in this document. Write output to and take input from standard system APIs rather than direct from hardware controls where possible. This will enable the I/O to be redirected from or to assistive technology devices - for example, screen readers and braille devices often redirect output (or copy it) to a serial port, while many devices provide character input, or mimic mouse functionality. The use of generic APIs makes this feasible in a way that allows for interoperability of the assistive technology with a range of applications. User agents should use standard rather than custom controls when designing user agents. Third-party assistive technology developers are more likely able to access standard controls than custom controls. If you must use custom controls, review them for accessibility and compatibility with third-party assistive technology. For information about rapid access to Microsoft Internet Explorer's DOM through COM, refer to [BHO]. __________________________________________________________ 5.3 Provide programmatic read and write access to user agent functionalities and user interface controls. [Priority 1] Refer also to checkpoint 5.2. 5.4 Implement selection and focus mechanisms and make the selection and focus available to users and through APIs. [Priority 1] Refer also to checkpoint 7.1 and checkpoint 5.3. 5.5 Provide programmatic notification of changes to content and user interface controls (including selection and focus). [Priority 1] Refer also to checkpoint 5.2. 5.6 Comply with W3C Document Object Model specifications and export interfaces defined by those specifications. [Priority 1] For example, refer to [DOM1] and [DOM2]. User agents should export these interfaces using available operating system conventions. Note. The DOM Level 1 specification states that "DOM applications may provide additional interfaces and objects not found in this specification and still be considered DOM compliant." Techniques: [Ed. Need to emphasize more of what DOM can do.] A Document Object Model (DOM) is an interface to a standardized tree structure representation of a document. This interface allows authors to access and modify the document with client-side scripting language (e.g., JavaScript) in a consistent manner across scripting languages. As a standard interface, a DOM makes it easier not just for authors but for assistive technology developers to extract information and render it in ways most suited to the needs of particular users. Information of particular importance to accessibility that must be available through the DOM includes: + Content, including alternative content. + Style sheet information (for user control of styles). + Script and event handlers (for device-independent control of behavior). + The document structure (for navigation, creation of alternative views). User agents should support W3C DOM Recommendations, including [DOM1] and [DOM2]]. The W3C Recommendation for DOM Level 1 ([DOM1]) provides access to HTML and XML document information. The DOM Level 2 ([DOM2]) is made of a set of core interfaces to create and manipulate the structure and contents of a document and a set of optional modules. These modules contain specialized interfaces dedicated to XML, HTML, an abstract view, generic stylesheets, Cascading Style Sheets, Events, traversing the document structure, and a Range object. It is important to note that DOM is designed to be used on a server as well as a client and therefore many user interface-specific information such as screen coordinate information is not relevant and not supported by the DOM specification. Assistive technologies also require information about browser highlight mechanisms (e.g., the selection and focus) that may not be available through the W3C DOM. Note. The WAI Protocols and Formats Working Group is focusing its efforts on the DOM as the conduit from which to extract accessibility information from and to enhance the accessibility of a rendered document through a user agent. It is this are should concentrate on for providing access to user agent documents. __________________________________________________________ 5.7 Provide programmatic exchange of information in a timely manner. [Priority 2] This is important for synchronous alternative renderings and simulation of events. 5.8 Follow operating system conventions and accessibility settings. In particular, follow conventions for user interface design, default keyboard configuration, product installation, and documentation. [Priority 2] Refer also to checkpoint 10.4. Techniques: Develop the UA User Interface (UI) with standard interface components per the target platform(s). Most major operating system platforms provide a series of design and usability guidelines, these should be followed when possible (see platforms below). These checklists, style guides, and human interface guidelines provide very valuable information for developing applications (e.g., UAs) for any platform/operating system/GUI. If your custom interface cannot provide information or operation as defined above, then you may need to design your UA using any additional options provided by that platform. For instance, software should use the standard interface for keyboard events rather than working around it. Evaluate your standard interface components on the target platform against any built in operating system accessibility functions (see Appendix 8) and be sure your UA operates properly with all these functions. For example, take caution with the following: + Microsoft Windows supports an accessibility function called "High Contrast". Standard window classes and controls automatically support this setting. However, applications created with custom classes or controls must understand how to work with the "GetSysColor" API to ensure compatibility with High Contrast. + Apple Macintosh supports an accessibility function called "Sticky Keys". Sticky Keys operates with keys the operating system understands to be defined as modifier keys, and therefore a custom UA control should not attempt to define a new modifier key. Some guidelines for specific platforms: + "Macintosh Human Interface Guidelines" [APPLE-HI] Apple Computer Inc. + "IBM Guidelines for Writing Accessible Applications Using 100% Pure Java" [JAVA-ACCESS]. + "An ICE Rendezvous Mechanism for X Window System Clients" [ICE-RAP]. + "Information for Developers About Microsoft Active Accessibility" [MSAA]. + "The Inter-Client communication conventions manual" [ICCCM]. + "Lotus Notes accessibility guidelines" [NOTES-ACCESS]. + "Java accessibility guidelines and checklist" [JAVA-CHECKLIST]. + "The Java Tutorial. Trail: Creating a GUI with JFC/Swing" [JAVA-TUT]. + "The Microsoft Windows Guidelines for Accessible Software Design" [MS-SOFTWARE]. General guidelines for producing accessible software: + "Accessibility for applications designers" [MS-ENABLE]. + "Application Software Design Guidelines" [TRACE-REF]. + "Designing for Accessibility" [SUN-DESIGN]. + "EITAAC Desktop Software standards" [EITAAC]. + "Requirements for Accessible Software Design" [ED-DEPT]. + "Software Accessibility" [IBM-ACCESS]. + Towards Accessible Human-Computer Interaction" [SUN-HCI]. + "What is Accessible Software" [WHAT-IS]. + Accessibility guidelines for Unix and X Window applications [XGUIDELINES]. Support System Conventions for loading Assistive Technologies: User agents should support operating system or application environment (e.g., Java) conventions for loading assistive technologies. In the case of Java applets, the browser's Java Virtual Machine should support the Sun convention for loading an assistive technology. Writing an application that follows the Java system conventions for accessible software does not allow the applet to be accessible if an assistive technology designed for that environment cannot be run to make the applet accessible. Refer to the appendix on loading assistive technologies for DOM access for information about how an assistive technology developer can load its software into a Java Virtual Machine. __________________________________________________________ Guideline 6. Implement open specifications and their accessibility features 6.1 Implement the accessibility features of supported specifications (markup languages, style sheet languages, metadata languages, graphics formats, etc.). [Priority 1] Refer also to checkpoint 1.1. Note. The Techniques Document ([UA-TECHNIQUES]) discusses accessibility features of W3C specifications. Techniques: + The accessibility features of Cascading Style Sheets (refer to [CSS1] and [CSS2]) are described in [CSS-ACCESS]. + The accessibility features of SMIL 1.0 (refer to [SMIL]) are described in [SMIL-ACCESS]. + The following is a list of accessibility features of [HTML40]: o Support the "alt" attribute defined for the IMG, AREA, INPUT, and APPLET elements. o Support the "longdesc" attribute defined for IMG elements ([HTML40], section 13.2). This attribute may be used to attach additional descriptive information to images if the "alt" description is insufficient. o Support the CAPTION element ([HTML40], section 11.2.2) for rich table captions. o Support the ACRONYM and ABBR elements ([HTML40], section 9.2.1) for acronyms and abbreviations. o Support the "summary" attribute for TABLE ([HTML40], section 11.2.1) for table summary information. o Support table elements (THEAD, TBODY, TFOOT, COLGROUP, and COL) that group table rows and columns into meaningful sections. o Support attributes ("scope", "headers", and "axes") so that non-visual browsers may render a table in a linear fashion, based on the semantically significant labels. o Support the "scope", header", and help users keep track of header information. o Support the NOSCRIPT element ([HTML40], sections 18.3.1 and 16.4.1) for accessible alternatives to scripts. o Support the NOFRAMES element ([HTML40], sections 18.3.1 and 16.4.1) for accessible alternatives to frames. o Support the "lang" attribute ([HTML40], section 8.1). o Support the "tabindex" attribute ([HTML40], section 17.11.1) for assigning the order of keyboard navigation within a document. o Support the "accesskey" attribute ([HTML40], section 17.11.2) for assigning keyboard commands to active components such as links, and form controls. __________________________________________________________ 6.2 Implement W3C specifications when they are appropriate for a task. [Priority 2] For instance, for markup, support [HTML40] or [XML]. For style sheets, support [CSS1], [CSS2], or XSL. For mathematics, support [MATHML]. For synchronized multimedia, support [SMIL]. For access to the structure of HTML or XML documents, support [DOM1]. For an event model, support [DOM2]. Refer also to checkpoint 5.6. Guideline 7. Provide navigation mechanisms 7.1 Allow the user to navigate viewports (including frames). [Priority 1] Note. For example, when all frames of a frameset are displayed side-by-side, allow the user to navigate among them with the keyboard. Or, when frames are displayed individually (e.g., by a text browser or speech synthesizer), provide a list of links to individual frames. Navigating into a viewport makes it the current viewport. Techniques: + Some operating systems provide a means to navigate among all windows, not just those created by the user agent. This suffices for viewports that are windows. However user agents may also allow the user to shift the focus from window to window independent of the standard operating system mechanism. + Consult the section on frame techniques. __________________________________________________________ 7.2 For user agents that offer a browsing history mechanism, when the user returns to a previous view, restore the point of regard in the viewport. [Priority 1] For example, when users navigate "back" and "forth" among views, for each view they should find the viewport position where they left it. 7.3 Allow the user to navigate just among table cells of a table (notably left and right within a row and up and down within a column). [Priority 1] Note. Navigation techniques include keyboard navigation from cell to cell (e.g., using the arrow keys) and page up/down scrolling. Refer also to checkpoint 1.1 and checkpoint 5.3. Techniques: All users should be able to quickly determine the nature and purpose of a table. Examining the table visually often conveys a sense of the table contents with a quick scan of the cells. Users with blindness or low vision, users who have difficulty translating printed material, or users in an eyes-busy or speech-based environment may not able to do this. Providing table summary information, when first navigating to a table allows the nature of a table to be easily determined. In HTML, summary information for tables comes from the "summary" attribute on the TABLE element as well as the CAPTION element. An auditory rendering agent, when the point-of-regard moves to a table, might say, "Table: Tax tables for 1998," thus identifying the nature of the table. The user could then use keyboard commands to move the selection to the next logical block of information, or use a different command to "burrow" into the table. The "burrow" command should have an opposite "up" command, which would move the selection from an individual cell to the table as a whole, so that the user can leave a table from any cell within it, rather than navigating to the end. If the user moves the focus up to look over the summary information, it should be possible to burrow back to the same cell. When navigating a table that contains another table, this strategy can avoid confusion. For example, if each row of a table contained five cells, but the second row contained a 4x4 table in the third cell, a user could be disoriented when the row did not end as expected. However, when the selection moved to the third cell of the table, a compliant browser would report that this was a table, and describe its contents. The user would have the option of navigating to the forth cell of the parent table, or burrowing into the table within this cell. When rendering tabular information, the fact that it is tabular information should be apparent. For a graphical user agent, such information is commonly made obvious by the border attribute or by visually apparent aligned white space between columns. However, for a non-graphical agent, such information must also be made evident. As the user agent shifts the selection to a table, it should first allow users to access summary information about the table (e.g., the CAPTION element or the "summary" attribute in HTML). Access to this information allows the user to determine whether or not to examine the contents of the table, or to move the selection to the next block of content. Users should be able to choose not to have the summary information presented, if, for example, they visit a table frequently and don't want to hear the summary information repeated each time. In many data tables, the meaning of the contents of a cell are related to the contents of adjacent cells. For example, in a table of sales figures, the sales for the current quarter might be best understood in relation to the sales for the previous quarter, located in the adjacent cell. In order to provide access to contextual information for individuals using non-graphical browsers, or for individuals with certain types of learning disabilities, it is necessary for the user agent to allow the selection to be moved from cell to cell, both right/left and up/down via keyboard commands. The UA should inform the user when navigation has led to a table edge. The most direct method of performing such navigation would be via the cursor keys, though other navigation strategies might be used. Users of graphical browsers can easily locate cells within a table that are at the intersection of a row and column of interest. To provide equivalent access to users of non-graphical browsers, equivalent means of navigation should be provided. The search function of a browser will allow the user to locate key terms within a table, but will not allow the user to find cells that are at the intersection of rows and columns of interest. More techniques: + An advanced search mode might provide entries for header information, allowing the user to find information at the intersection of columns and rows using the key terms. + A search mode might allow the user to search for key terms that are related to key header terms, allowing searches to be restricted to specific rows or headers within a table. The header information visible in a TH cell may be abbreviated, in which case it should be user preference to see the "abbr" value if any or the full contents. Axis information may also help the user search into confined portions of the table. Column groups and row groups are other confining partitions of a table in which a search may be limited. Software: + Table navigation script from the Trace Center __________________________________________________________ 7.4 Allow the user to navigate all active elements. [Priority 1] Navigation mechanisms may range from sequential (e.g., serial navigation by tabbing) to direct (e.g., by entering link text) to searching on active elements only (e.g., based on form control text, associated labels, or form control names). 7.5 Allow the user to navigate just among all active elements. [Priority 2] Refer also to checkpoint 7.4. Techniques: Sequential navigation includes all active elements. User agents might provide other navigation mechanisms limited to a particular type of element. For example "Find the next table" or "Find the previous form". The following techniques suggest some types of navigation. + Serial navigation. It is important that application developers maintain a logical keyboard navigation order. The navigation order is defined as the order of navigation among components and component elements via the keyboard. Generally users navigate by tabbing between components or groups and using the arrow keys within a component group or component's elements. The ability to tab between software components is a key feature in the implementation of keyboard accessibility. (Cross-reference to keyboard access.) Buttons of common functionality, such as a set of radio buttons used to set the location of a panel (top left, bottom left, and so on.), should be grouped together so the first element of the visible group can be tabbed to. Allow the user to use the arrow keys to navigate to each end of the group. + How to indicate that something is in tabbing order in Java: A component is inclusive in the tabbing order when added to a panel and its isFocusTraversable() method returns true. A component can be removed from the tabbing order by simply extending the component, overloading this method, and returning false. + For active elements, navigation to the previous or next active element. + In a table, up/down and left/right. Direct navigation: Excessive use of serial navigation can reduce the usability of software for both disabled and non-disabled users. As a developer, you need to determine the point at which tabbing gets in the way and provide a keyboard alternative. This is done through the use of keyboard shortcuts. Note that user agents must provide information about available shortcuts (the current keyboard configuration) to users. + Need for element identification. + Access by position in document. + Next/Previous occurrence of text in an element's content (e.g., first letter) in the current document. + In a table, access to cell based on coordinates. __________________________________________________________ 7.6 Allow the user to search for rendered text content, including alternative text content. [Priority 2] Techniques: + Allow users to search for element content and attribute values (human-readable ones). + Allow users to search the document source view. + For forms, allow users to find required controls. Allow users to search on labels as well as content of some controls. + Allow the user to search among just alternative text. + For multimedia presentations: o Allow users to search and examine time-dependent media elements and links in a time-independent manner. For example, present a static list of time-dependent links. o Allow users to search closest timestamp from a text stream or a media elements or links and find other media elements active at the same time. o Allow users to view a list of all media elements or links of the presentations sorted by start or end time or alphabetically. o For frames, allow users to search for content in all frames (without having to be in a particular frame). __________________________________________________________ 7.7 Allow the user to navigate according to structure. [Priority 2] For example, allow the user to navigate familiar elements of a document: paragraphs, tables, headers, lists, etc. Techniques: + DOM is minimal (tree navigation) + Best navigation will involve a mix of source tree information and rendered information. + May use commonly understood document models rather than strict DTD navigation. E.g., properly nesting headers in HTML. Headers should be used only to convey hierarchy, not for graphical side-effects. + Goal of simplifying the structure view as much as possible. + Allow the user to control level of detail/ view of structure. + Depth first as well as breadth first possible. Allow next/previous sibling, up to parent, and end of element. + Navigation of synchronized multimedia: allow users to stop, pause, fast forward, advance to the next clip, etc. Skipping navigation bars: Author-supplied navigation mechanisms such as navigation bars at the top of each page may force users with screen readers or some physical disabilities to wade through numerous links on each page of a site. User agents may facilitate browsing for these users by allowing them to skip recognized navigation bars (e.g., through a configuration option). Some techniques for doing so include: 1. Provide a functionality to jump to the first non-link content. 2. In HTML, the MAP element may be used to mark up a navigation bar (even when there is no associated image). Thus, users might ask that MAP elements not be rendered in order to hide links inside the MAP element. Note. Starting in HTML 4.0, the MAP element allows block content, not just AREA elements. __________________________________________________________ 7.8 Allow the user to configure structured navigation. [Priority 3] For example, allow the user to navigate only paragraphs, or only headers and paragraphs, etc. Techniques: + Allow the user to navigate by element type. + Allow the user to expand or shrink portions of the structured view (control detail level) for faster access to important parts content. __________________________________________________________ Guideline 8. Help orient the user 8.1 Provide a mechanism for highlighting and identifying (through a standard interface where available) the current viewport, selection, and focus. [Priority 1] Note. This includes highlighting and identifying frames. Refer also to checkpoint 9.1.. Techniques: + If colors are used to highlight the current viewport, selection, or focus, allow the user to set preferred colors and to ensure sufficient contrasts. + If the current viewport is a window, allow the user to cause the window to pop to the foreground. + If the current viewport is a frame or the user doesn't want windows to pop to the foreground, use colors, reverse videos, or other visual clues to indicate the current viewport. For speech or braille output, render the title or name of a frame or window and indicate changes in the current viewport. Refer also to the section on frame techniques __________________________________________________________ 8.2 Provide access to table cell header information. [Priority 1] Refer also to checkpoint 5.3. Techniques: + Refer to the section on table techniques + Allow the user to access this information on demand (e.g., by activating a menu or keystroke). __________________________________________________________ 8.3 Provide an outline of a resource view built from its structural elements (e.g., frames, headers, lists, forms, tables, etc.) [Priority 2] For example, for each frame in a frameset, provide a table of contents composed of headers where each entry in the table of contents links to the header in the document. 8.4 Indicate whether a focused link has been marked up to indicate that following it will involve a fee. [Priority 2] Note. [MICROPAYMENT] describes how authors may mark up micropayment information in an interoperable manner. This information may be provided through the standard user interface provided the interface is accessible. Thus, any prompt asking the user to confirm payment must be accessible. Techniques: + Refer to the section on link techniques. + Allow the user to access this information on demand (e.g., by activating a menu or keystroke for a focused link). __________________________________________________________ 8.5 Provide information to help the user decide whether to follow a focused link. [Priority 2] Note. Useful information includes: whether the link has already been visited, whether it designates an internal anchor, the type of the target resource, the length of an audio or video clip that will be started, and the expected natural language of target resource. Techniques: + Refer to the section on link techniques. + Allow the user to access this information on demand (e.g., by activating a menu or keystroke). __________________________________________________________ 8.6 Allow the user to configure the outline view. [Priority 3] For example, allow the user to control the level of detail of the outline. Refer also to checkpoint 5.3. 8.7 Allow the user to configure what information about links to present. [Priority 3] Note. Using color as the only distinguishing factor between visited and unvisited links does not suffice since color may not be perceivable by all users or rendered by all devices. Refer also to checkpoint 8.5. Techniques: Allow the user to access this information on demand (e.g., by activating a menu or keystroke). __________________________________________________________ 8.8 Provide a mechanism for highlighting and identifying (through a standard interface where available) active elements. [Priority 3] Note. User agents may satisfy this checkpoint by supporting the appropriate style sheet mechanisms, such as link highlighting. 8.9 Maintain consistent user agent behavior and default configurations between software releases. Consistency is less important than accessibility and adoption of operating system conventions. [Priority 3] In particular, make changes conservatively to the layout of user interface controls, behavior of existing functionalities, and default keyboard configuration. Guideline 9. Notify the user of content and viewport changes 9.1 Provide information about user agent-initiated content and viewport changes directly to the user and through APIs. [Priority 1] For example, inform the users when a script causes a popup menu to appear. Techniques: Refer to the section on frame techniques __________________________________________________________ 9.2 Ensure that when the selection or focus changes, it is in the viewport after the change. [Priority 2] 9.3 Prompt the user to confirm any form submission triggered indirectly, that is by any means other than the user activating an explicit form submit control. [Priority 2] For example, do not submit a form automatically when a menu option is selected, when all fields of a form have been filled out, on a mouseover event, etc. 9.4 Allow the user to configure notification preferences for common types of content and viewport changes. [Priority 3] For example, allow the user to choose to be notified (or not) that a script has been executed, that a new viewport has been opened, that a pulldown menu has been opened, that a new frame has received focus, etc. Techniques: Refer to the section on frame techniques __________________________________________________________ 9.5 When loading content (e.g., document, video clip, audio clip, etc.) indicate what portion of the content has loaded and whether loading has stalled. [Priority 3] Techniques: Status information - on resource loading - should be provided in a device-independent manner. Techniques include text and non-text status indicators. Users should be able to request status information or have it rendered automatically. User agents may allow users to configure when status information should be rendered (e.g., by hiding or showing the status bar). Screen readers may provide access on demand (e.g., through the keyboard) to the most recent status information, or to announce the new information whenever it changes. Useful status information: + Document proportions (numbers of lines, pages, width, etc.) + Number of elements of a particular type (e.g., tables) + The viewport is at the beginning or end of the document. + Size of document in bytes. User agents may allow users to configure what status information they want rendered. Allow users to access status information on demand through a keyboard or other shortcut. __________________________________________________________ 9.6 Indicate the relative position of the viewport in content (e.g., the percentage of an audio or video clip that has been played, the percentage of a Web page that has been viewed, etc.). [Priority 3] Note. Depending on how the user has been browsing, the percentage may be calculated according to focus position, selection position, or viewport position. Guideline 10. Allow the user to configure the user agent 10.1 Provide information about the current input configuration (e.g., keyboard bindings). [Priority 1] Techniques: Tabbing order: + How to specify in HTML Keyboard shortcuts + How to specify in HTML + Visibility of. + Documentation of. At a minimum: list in README file that comes with software. Some suggestions: 1. Allow the user to use the find command to jump to a link instead of tabbing there. It would save a lot of keystrokes, especially if one programs the keystrokes as macros. But this requires that focus moves to the location that find highlights. 2. Allow the user to use find command to jump to text in buttons. 3. Allow the user to use find command to jump to image by searching on its alternative content (e.g., "alt" attribute). 4. Allow the user to separate setting the focus and activating the control. For links, first-time users of a page may want to hear link text (focus) before deciding whether to follow the link (activate). More experienced users of a page would prefer to follow the link directly, without the intervening focus step. Some reserved keyboard shortcuts are listed in the appendix on accessibility features of some operating systems. __________________________________________________________ 10.2 Allow the user to change and control the input configuration. [Priority 2] For example, allow the user to configure the user agent for single-key activation of functionalities. For self-voicing browsers, allow the user to modify what voice commands activate functionalities. Similarly, allow the user to modify the graphical user interface for quick access to commonly used functionalities (e.g., through buttons). Techniques: User agents that allow users to customize or reconfigure mappings from keyboard, voice, etc. to user agent functionalities should allow each mapping to be accompanied by a description so that the user can understand the mapping. For example, if "Control-P" maps to a print functionality, a short description would be "Print" or "Print setup". + Profiles + Default values + Device-independent configuration When using a physical keyboard, some users require single-key access, others require that keys activated in combination be physically close together, while others require that they be spaced physically far apart. When allowing users to configure keyboard access to functionalities, user agents must consider operating system conventions, author-specified shortcuts, and user preferences. The user agent's default configuration should include shortcuts for frequently performed actions and should respect operating system conventions. User agents, to allow the user to turn on and off author-specified keyboard configurations, may offer a checkbox in the keyboard mapping dialog to that would toggle the support for author-specified keyboard configurations. In [HTML40], authors may specify keyboard behavior with the "tabindex" and "accesskey" attributes. [Ed. New section. Users must be allowed to control keyboard configuration based on specific needs. For poor motor control, keys far apart on a regular keyboard. For poor mobility, keys close together. General principle: fewest keystrokes, short distance to move.] __________________________________________________________ 10.3 Use operating system conventions to indicate the input configuration. [Priority 2] For example, on some operating systems, if a functionality is available from a menu, the letter of the key that will activate that functionality is underlined. Techniques: In some operating systems, information about shortcuts is rendered visually using an underscore under a character in a menu item or button corresponding to the shortcut key activated with an ALT+character. For menu accelerators the text in the menu item is often followed by a CNTRL+function key. These are conventions used by the Sun Java Foundations Classes (refer to [JAVA-TUT]) and Microsoft Foundations Classes for Windows. __________________________________________________________ 10.4 Avoid default input configurations that interfere with operating system conventions. [Priority 2] For example, the default configuration should not include "Alt-F4" or "Control-Alt-Delete" on operating systems where that combination has special meaning to the operating system. In particular, default configurations should not interfere with the mobility access keyboard modifiers reserved for the operating system. Refer also to guideline 5. 10.5 Allow the user to configure the user agent in named profiles that may be shared (by other users or software). [Priority 2] Users must be able to select from among available profiles or no profile (i.e., the user agent default settings). Techniques: Cascading Style Sheets may be part of a source document or linked externally. Stand-alone style sheets are useful for implementing user profiles in public access computer environments where several people use the same computer. User profiles allow for convenient customization and may be shared by a group. Configuration profiles allow individual users to save their user agent settings and re-apply them easily. This is particularly valuable in an environment where several people may use the same machine. The user should be able to easily transfer profiles between installations of the same user agent. One way to facilitate this is to follow applicable operating system conventions for profiles. Users should be able to switch rapidly between profiles (or the default settings). This is helpful when: + Several people use the same machine. + One user is being helped by another who may not recognize the information being displayed using the user's profile. User agents may apply a profile when the user logs in. They may also allow users to apply settings interactively, for example by allowing them to choose from a list of named profiles in a menu. Sample profiles (based on common usage scenarios) can assist users in the initial set up of the user agent. These profiles can serve as models and may be copied and fine-tuned to meet an individual's particular needs. __________________________________________________________ 10.6 Provide default input configurations for frequently performed operations. [Priority 3] In particular, provide convenient mappings to functionalities that promote accessibility such as navigation of links. 10.7 Allow the user to configure the graphical arrangement of user interface controls. [Priority 3] Techniques: + Allow multiple icon sizes. __________________________________________________________ Guideline 11. Provide accessible product documentation and help 11.1 Provide a version of the product documentation that conforms to the Web Content Accessibility Guidelines. [Priority 1] Refer to [WAI-WEBCONTENT]. Techniques: Documentation created in HTML should follow the [WAI-WEBCONTENT]. Electronic documentation created in open standard formats such as HTML and ASCII can often be accessed in the user's choice of application such as a word processor or browser. Accessing documentation in familiar applications is particularly important to users with disabilities who must learn the functionalities of their tools and be able to configure them for their needs. Commonly used applications are also more likely to be compatible with assistive technology. Electronic documentation should not be provided in proprietary formats. Users with print impairments may need or desire documentation in alternative formats such as Braille, large print, or audio tape. User agent manufacturers may provide user manuals in alternative formats. Documents in alternative formats can be created by agencies such as Recording for the Blind and Dyslexic and the National Braille Press. User instructions should be expressed in an input device-independent manner. Provide instructions for using or configuring the user agent in a manner that can be understood by a user of any input device including a mouse or keyboard. For example, "Select the Home button on the toolbar" or "Select Home from the Go menu to return to the Home page." Universal design means that access to features that help accessibility should be integrated into standard menus. User agents should avoid regrouping access to accessibility features into specialized menus. __________________________________________________________ 11.2 Document all user agent features that promote accessibility. [Priority 1] For example, review the documentation or help system to ensure that it discusses the functionalities addressed by the checkpoints of this document. Techniques: Include references to accessibility features in these parts of the documentation: 1. Indexes. Include terms related to product accessibility in the documentation index (e.g., "accessibility", "disability" or "disabilities"). 2. Tables of Contents. Include terms related to product accessibility in the documentation table of contents (e.g., features that promote accessibility) 3. Include instructions on how to modify all user configurable defaults and preferences (e.g, images, video, style sheets, and scripts) as specified by the documentation. 4. Include a list of all keyboard shortcuts or other input configuration information in the accessibility section of the documentation. __________________________________________________________ 11.3 Document the default input configuration (e.g., default keyboard bindings). [Priority 1] For example, documentation of what user agent features may be activated with a single keystoke, voice command, or button activation is an important part of the user interface to users visual impairments, some types of movement impairments, or multiple disabilities. Without this documentation,these users may not realize they can accomplish a particular task with a single gesture and so might unnecessarily avoid that feature of the software. Or they might waste time and energy using a very inefficient technique to perform a task. 11.4 In a dedicated section, document all features of the user agent that promote accessibility. [Priority 2] _________________________________________________________________ 3 Accessibility Topics This section introduces some general techniques to promote accessibility in user agent functionality. A list of assistive technologies and browsers designed for accessibility is available at the WAI Web site (refer to [USERAGENTS]). 3.1 User control of style To ensure accessibility, users must have final control over certain renderings. * For changing text size, allow font size changes or provide a zoom mechanism. * To hide content, use the 'display' and 'visibility' properties of [CSS1]. Implement CSS ([CSS1], [CSS2]) including the CSS2 cascade order and user style sheets. The CSS2 cascade order ensures that user style sheets with "!important" take precedence over author style sheets, giving users final control. Style sheets give authors design flexibility while offering users final control over presentation (refer also to [WAI-WEBCONTENT], checkpoint 3.3). CSS should be implemented by user agents that implement CSS for text that it renders. CSS includes properties for audio, braille (fixed and refreshable), screen, and print rendering, and all relevant properties for supported output media should be implemented. Note that in the CSS cascade order, markup is given less weight than style sheet rules. Thus, an author may use both presentation markup and style sheets, and user agents that support style sheets will prefer the latter. A user style sheet can be implemented through a user interface, which means that the user may not have to understand how to write style sheets; they are generated or the user agent acts as though they were. For an example of this, refer to the style sheets implementation of Amaya ([AMAYA]), which provides a GUI-based interface to create and apply internal style sheets. The same technique could be used to control a user style sheet. For images, applets, and animations: Background images may be controlled by the use of local style sheets, and more effectively if these can be dynamically updated. Animation rate depends on the players used. User agents that provide native rendering of animation (for example a movie player, a driver for animated GIF images, or a java machine) should enable the control of animation rates, or at least allow the user to stop, and to play frame-by-frame, as well as straight rendering. A user agent could provide control of the general timing of a presentation, combined with the ability to select from available tracks manually. An issue to bear in mind is that when animation is synchronized with audio, a user may need the ability to play the animation separately from the associated audio. For time-based presentations: Implement user controls to start, atop, rewind and pause presentations, and where multiple tracks are supported, to choose which tracks should be rendered. SMIL ([SMIL]) provides for a number of these features. A SMIL implementation should provide for direct user control, as well as activation of the controls through a published API, for developers of assistive technologies. For user agents rendering audio: On selecting from among available description tracks. SMIL ([SMIL]) allows users to specify captions in different languages. By setting language preferences in the SMIL player, users may access captions (or audio) in different languages. The G2 player from Real Networks currently allows users to specify which language they prefer, which can be evaluated in a SMIL document to choose from among text or audio tracks. Currently only one language can be indicated which does not permit choosing, for example, English spoken audio with Spanish captions. The Quicktime player currently permits turning on and off any number of tracks individually, which can include audio, video, and text. For user agents rendering video: Implement the CSS positioning and/or SMIL layout languages. Allow the user to freeze a presentation, manually move and resize component video tracks (including captions, subtitles and signed translations) and to apply CSS stylesheets to text-based presentation and SVG. For user agents rendering speech: CSS2 ([CSS2]]) properties for speech can allow users to control speech rate, volume, and pitch. These can be implemented by allowing the user to write and apply a local style sheet, or can be automatically generated by means of (accessible) user controls, which should also be controllable through an API. User interface: * Allow the user to select large or small buttons and controls (and ensure that these values are applied consistently across the user interface) @@CMN: Opera does this.@@ * Allow the user to control features such as menu font sizes, or speech rates - this may be achieved through use of operating system standards. * Allow the user to regroup buttons and controls, and reorder menus (@@CMN: MS Word does this. This is also related to reconfiguring commands, etc.@@) 3.2 Link techniques [Ed. Talk about CSS pseudo-classes for :hover] [Ed. Talk about using :before to clearly indicate that something is a link (e.g., 'A:before { content : "LINK:" }')] * Address broken link handling so that it doesn't disorient users. For example, leave viewport as is and notify user. * Provide the user with media-independent information about the status of a link as the link is chosen. For example, do not rely solely on font styles or color changes to alert the user whether or not the link has previously been followed. The user should be able to pick from amongst a list of alert mechanisms (i.e. color changes, sound clips, status line messages, etc.), and should not be limited to only one type of alert mechanism. + For assistive technologies: Provide the user with the option to have the TITLE (if present) or the hyperlink text made available to the user when the user navigates from link to link. * Alert the user if following a link involves the payment of a fee. * When presenting the user with a list of the hyperlinks contained in a document, allow the user to choose between "Display links using hyperlink text" or "Display links by title (if present)", with an option to toggle between the two views. + Provide the user with orientation information about the listed links. For example, identify a selected link as "Link X of Y", where "Y" is the total number of links available in the document. * Offer the user a list of links which have been visited and a list of links which have not yet been visited, or provide a media-independent mechanism to distinguish between visited and unvisited links. Do _not_ rely on visual or aural prompts alone to signify the difference between visited and unvisited links. * Offer the user a list of links which are internal (i.e., local to document) and those which are external, or provide a media-independent mechanism to distinguish between external and internal links in a list of links. Do _not_ rely on visual or aural prompts *alone* to signify the difference between internal and external links. Lynx ([LYNX]) numbers each link and other element and provides information about the relative position of the section of the document. Position is relative to the current page and the number of the current page out of all pages. Each page usually has 24 lines. Information about link status and other properties can be provided in an information view such as that provided by Netscape Navigator about how many and what types of elements are in a document. User agents should not consider that all local links (to anchors in the same page) have been visited when the page has been visited. User agents may use graphical or aural icons to indicate visited links or broken links. Users should be able to: * Configure what information about links they wish presented to them. * Turn on and off automatic rendering of this information when a link is focused. * Get information about a focused link on demand, even if automatic rendering has been turned off. 3.3 Table techniques Tables were designed to structure relationships among data. In graphical media, tables are often rendered on a two-dimensional grid, but this is just one possible interpretation of the data. On the Web, the HTML TABLE element has been used more often than not to achieve a formatting effect ("layout tables") rather than as a way to structure true tabular data ("data tables"). Layout tables cause problems for some screen readers and when rendered, confuse users. Even data tables can be difficult to understand for users that browse in essentially one dimension, i.e. for whom tables are rendered serially. The content of any table cell that visually wraps onto more than one line can be a problem. If only one cell has content that wraps, there is less problem if it is in the last column. Large tables pose particular problems since remembering cell position and header information becomes more difficult as the table grows. User agents facilitate browsing by providing access to specific table cells and their associated header information. How headers are associated with table cells is markup language-dependent. Tabular navigation is required by people with visual impairments and some types of learning disabilities to determine the content of a particular cell and spatial relationships between cells (which may convey information). If table navigation is not available users with some types of visual impairments and learning disabilities may not be able to understand the purpose of a table or table cell. 3.3.1 Table rendering A linear view of tables -- cells presented row by row or column by column -- can be useful, but generally only for simple tables. Where more complex structures are designed, allowing for the reading of a whole column from header downward is important as is carrying the ability to perceive which header belongs to which column or group of columns if more than one is spanned by that header. It is important for whole cells to be made available as chunks of data in a logical form. It might be that a header spans several cells so the header associated with that cell is part of the document chunk for that and each of the other cells spanned by that header. Inside the cell, order is important. It must be possible to understand what the relationships of the items in a cell are to each other. Properly constructed data tables generally have distinct TH head cells and TD data cells. The TD cell content gains implicit identification from TH cells in the same column and/or row. For layout tables, a user agent can assist the reader by indicating that no relationships among cells should be expected. Authors should not use TH cells just for their formatting purpose in layout tables, as those TH cells imply that some TD cells should gain meaning from the TH cell content. When a table is "read" from the screen, the contents of multiline cells may become intermingled. For example, consider the following table: This is the top left cell This is the top right cell of the table. of the table. This is the bottom left This is the bottom right cell of the table. cell of the table. If read directly from the screen, this table might be rendered as "This is the top left cell This is the top right cell", which would be confusing to the user. A user agent should provide a means of determining the contents of cells as discrete from neighboring cells, regardless of the size and formatting of the cells. This information is made available through the DOM [DOM1]). 3.3.2 Cell rendering Non-graphical rendering of information by a browser or an assistive technology working through a browser will generally not render more than a single cell, or a few adjacent cells at a time. Because of this, the location of a cell of interest within a large table may be difficult to determine for the users of non-graphical rendering. In order to provide equivalent access to these users, compliant browsers should provide a means of determining the row and column coordinates of the cell having the selection via keyboard commands. Additionally, to allow the user of a non-graphical rendering technology to return to a cell, the browser should allow a means of moving the selection to a cell based on its row and column coordinates. At the time the user enters a table, or while the selection is located within a table, the user agent should allow an assistive technology to provide information to the user regarding the dimensions (in rows and columns) of the table. This information, in combination with the summary, title, and caption, can allow the user with a disability to quickly decide whether to explore the table of skip over it. Dimensions is an appropriate term, though dimensions needn't be constants. For example a table description could read: "4 columns for 4 rows with 2 header rows. In those 2 header rows the first two columns have "colspan=2". The last two columns have a common header and two subheads. The first column, after the first two rows, contains the row headers. Some parts of a table may have 2 dimensions, others three, others four, etc. Dimensionality higher than 2 are projected onto 2 in a table presentation. The contents of a cell in a data table are generally only comprehensible in context (i.e., with associated header information, row/column position, neighboring cell information etc.). User agents provide users with header information and other contextual information. Techniques for rendering cells include: * Provide this information through an API. * Render cells as blocks. This may assist some screen readers. Using this strategy, the user agent might render individual cells with the relevant top and side headers attached. * Allow navigation and querying of cell/header information. When the selection is on an individual cell, the user would be able to use a keyboard command to receive the top and left header information for that cell. The user agent should appropriately account for headers that span multiple cells. * Allow users to read one table column or row at a time, which may help them identify headers. * Ignore table markup entirely. This may assist some screen readers. However, for anything more than simple tables, this technique may lead to confusion. 3.3.3 Cell header algorithm User agents should use the algorithm to calculate header information provided in the HTML 4.0 specification ([HTML40], section 11.4.3). Since not all tables are designed with the header information, user agents should provide, as an option, a "best guess" of the header information for a cell. Note that data tables may be organized top-to-bottom, bottom-to-top, right-to-left, and left-to-right, so user agents should consider all edge rows when seeking header information. Some repair strategies for finding header information include: * Consider that the top or bottom row to contains header information. * Consider that the leftmost or rightmost column in a column group contains header information. * If cells in an edge row or column span more than one row or column, consider the following row or column to contain header information as well. The user may choose the form and amount of this information, possibly announcing the row heads only once and then the column head or its abbreviation ("abbr") to announce the cell content. [Ed. The following issues were raised by Harvey Bingham.] 1. TH cells on both the left and right of the table need to be considered. 2. For TH cells with "rowspan" set: the content of those TH cells must be considered for each of the N-1 rows below the one containing that TH content. 3. An internal TH in a row surrounded on either side by TDs has no means to specify to which (row or column) that TH overrides what existed to its left or above it. 4. Finding column header cells assumes they are all above the TD cell to which they apply. 5. A TH with "colspan" set needs to be included in the list of TH for the M-1 columns to the right of the column in which the TH is found. 3.3.4 Table metadata Users of screen readers or other serial access devices cannot easily glean information about a page "at a glance". This is particularly difficult when accessing two-dimensional tables and trying to determine their content. Therefore, contextual information about tables (available from author-supplied markup or generated by the user agent) is very important to making them accessible. Text metadata about tables can come from a number of elements, attributes, the structure of the table itself, or other sources. Useful information to make available to users includes: * The number of column groups and columns. * The number of row groups and rows, in particular information about table headers and footers. * Which rows contain header information (whether at the top or bottom of the table). * Which columns contain header information (whether at the left or right of the table). * Whether there are subheads. * How many rows or columns a header spans. * The row/column dimensions of the table. 3.4 Frame techniques Frames were originally designed for use by graphical user interfaces to allow the graphical viewport to be broken up into pieces that could change independently (e.g,. selecting an entry in a table of contents in one frame changes the contents of a second frame). However Frames can pose problems users who rely on synthesized speech, refreshable braille, and magnified views. Problems include: * Orientation: What frame am I in? How is the frameset organized? What is the relationship among frames? What happens in frame B when I select a link in frame A? * Navigation: How do I get from frame to frame? To help users, user agents should: * Consider the author's alternative presentation to frames (e.g., provided by NOFRAMES in [HTML40]). * Inform the user that they are viewing a frameset. * Provide information about the number of frames in the frameset. * Provide (possibly nested) lists of links to each frame in the frameset. The link text can be the frame title (given by "title" or "name" if "title" is not present). Other alternative renderings for a frameset include simply rendering each frame in the frameset sequentially as a block (e.g., aligned vertically in a graphical environment). * Highlight the current frameset (e.g., with a thick border, by displaying the name of the current frameset in the status bar, etc. * Provide information about the current frame. Make available frame title for speech synthesizers and braille devices. * If a page does not have a list of links within in a frame available outside the frame, make the list available outside the frame. * Allow navigation between frames (forward and backward through the nested structure, return to global list of links to frames). * Allow the user to bookmark the current frame. * Inform the user if an action in one frame causes the content of another frame to change. Allow the user to navigate quickly to the frame(s) that changed. Frame structure information should be available through the DOM and appropriate accessibility interfaces. Using DOM and operating specific accessibility API to expose frame information provides one means for assistive technologies to provide alternative control of frames and rendering of frame information. The user agent should fully implement the DOM Level 1 Recommendation ([DOM1]) API related to frames: HTMLFrameSetElement, HTMLFrameElement, and HTMLIFrameElement. For people with visual impairments who are enlarge text on the screen to improve readability, frames become distorted and unusable. Other users with cognitive disabilities sometimes become disoriented in complex side-by-side frame configurations. To improve access to frames, user agents should allow frames to be viewed as a list so the user can identify the number of frames and the functions of each frame. If no frames information is present it should also be rendered so the user can optionally use that view of the information. Consider renderings of the following document: Time Value of Money <P>List of Presentation Slides</P> <OL> <LI><A HREF="slide001">Time Value of Money</A> <LI><A HREF="slide002">Topic Overview</A> <LI><A HREF="slide003">Terms and Short Hand</A> <LI><A HREF="slide004">Future Value of a Single CF</A> <LI><A HREF="slide005">Example 1: FV example:The NBA's new Larry Bird exception</A> <LI><A HREF="slide006">FV Example: NBA's Larry Bird Exception (cont.)</A> <LI><A HREF="slide007">SuperStar's Contract Breakdown</A> <LI><A HREF="slide008">Present Value of a Single Cash Flow</A> <LI><A HREF="slide009">Example 2: Paying Jr, and A-Rod</A> <LI><A HREF="slide010">Example 3: Finding Rate of Return or Interest Rate</A> <LI><A HREF="slide011">Annuities</A> <LI><A HREF="slide012">FV of Annuities</A> <LI><A HREF="slide013">PV of Annuities</A> <LI><A HREF="slide014">Example 4: Invest Early in an IRA</A> <LI><A HREF="slide015">Example 4 Solution</A> <LI><A HREF="slide016">Example 5: Lotto Fever </A> <LI><A HREF="slide017">Uneven Cash Flows: Example 6:Fun with the CF function</A> <LI><A HREF="slide018">Example 6 CF worksheet inputs</A> <LI><A HREF="slide019">CF inputs continued</A> <LI><A HREF="slide020">Non-Annual Interest Compounding</A> <LI><A HREF="slide021">Example 7: What rate are you really paying?</A> <LI><A HREF="slide022">Nominal to EAR Calculator</A> <LI><A HREF="slide023">Continuous Interest Compounding</A> <LI><A HREF="slide024">FV and PV with non-annual interest compounding</A> <LI><A HREF="slide025">Non-annual annuities</A> <LI><A HREF="slide026">Example 8: Finding Monthly Mortgage Payment</A> <LI><A HREF="slide027">solution to Example 8</A> </OL> The following illustrate how some user agents handle this frameset. First, rendering in Microsoft Internet Explorer 5.0 on a Windows platform: Image shows the example frameset with five frame panes rendered in Microsoft Internet Explorer 5.0 Rendering by Lynx on Linux: Time Value of Money FRAME: Size buttons FRAME: Presentation Outline FRAME: Navigation buttons FRAME: Slide Image FRAME: Notes List of Presentation Slides 1. Time Value of Money 2. Topic Overview 3. Terms and Short Hand 4. Future Value of a Single CF 5. Example 1: FV example:The NBA's new Larry Bird exception 6. FV Example: NBA's Larry Bird Exception (cont.) 7. SuperStar's Contract Breakdown 8. Present Value of a Single Cash Flow 9. Example 2: Paying Jr, and A-Rod 10. Example 3: Finding Rate of Return or Interest Rate 11. Annuities 12. FV of Annuities 13. PV of Annuities 14. Example 4: Invest Early in an IRA 15. Example 4 Solution 16. Example 5: Lotto Fever 17. Uneven Cash Flows: Example 6:Fun with the CF function 18. Example 6 CF worksheet inputs 19. CF inputs continued 20. Non-Annual Interest Compounding 21. Example 7: What rate are you really paying? 22. Nominal to EAR Calculator 23. Continuous Interest Compounding 24. FV and PV with non-annual interest compounding 25. Non-annual annuities 26. Example 8: Finding Monthly Mortgage Payment 27. solution to Example 8 Graphical rendering by Home Page Reader on Windows: Image shows the example frameset with five links for each of the frame elements in IBM home page reader Audio rendering by Home Page Reader on Windows: @@add here@@ User agents may also indicate the number of frames in a document and which frame is the current frame via the menu bar or popup menus. Users can configure the user agent to include a FRAMES menu item in their menu bar. The menu bar makes the information highly visible to all users and is very accessible to assistive technologies. In the following snapshot, the menu bar indicates the number of frames and a check next to the name of the frame element indicates which is the current frame: Image shows a pull down menu indicating the number of frames in a document, the labels associated with each frame, and a check mark to indicate the current frame 3.5 Form techniques * For labels explicitly associated with form controls (e.g., "for" attribute on LABEL in HTML), make available label information when the user is navigating among the form controls. * Provide information about what is required for each form control. * Provide information about the order of form controls (e.g., as specified by "tabindex" in HTML). This is important since users that access forms serially need to know they have supplied all the necessary information before submitting the form. Statement of form submission problems from Gregory Rosmaita: Point A: As a user, I do not want to be prompted time I submit a form, provided that I submitted the form by activating its submit button. If, however, I simply hit the ENTER or the RETURN key from within a FORM control (i.e., rather than explicitly activating the SUBMIT mechanism), I would like the UA to request confirmation before submitting the form content. Point B: As a user, I do NOT want the form content automatically submitted if I inadvertently press the ENTER or RETURN key. PROBLEM STATEMENT FOR POINT B: Inadvertently pressing the RETURN or ENTER key is quite a prevalent phenomenon amongst users of every level of expertise - especially those who often find it necessary to switch between user agents. Lynx, for example, uses the ENTER key within FORMs as a means of exposing drop-down (or pop-up, depending upon your point of view) SELECT menus. Thus, when one encounters a SELECT menu using Lynx, one: exposes the content of the menu by pressing the ENTER key, and then is able to navigate between OPTIONs using the up and down arrows or via Lynx's text-search feature. When one finds the appropriate OPTION, it is selected by pressing ENTER, which causes the selected item to be displayed in the SELECT menu listbox. The problems posed by the default "submit on enter" feature of most GUI browsers, is not limited to the SELECT menu problem outlined above. Lynx (as well as several other text-based browsers) uses the ENTER/RETURN key as a means of toggling several FORM controls, such as the selection of checkboxes and radio buttons. Moreover, I would like to stress that the "Auto-Submit-On- Enter" feature is not only quite problematic for one operating in an eyes-free environment, but for those unaccustomed to using online forms, and for those unfamiliar with a particular user agent's default key- bindings for forms, as well as those (like myself and countless others) who surf the Web using a variety of browsers, often switching from browser to browser -- ALT- TAB-ing from Lynx32 to MSIE to Opera, for example -- in order to better comprehend the contents of a page or while attempting to navigate an poorly structured site or a poorly marked-up form Point C: As a speech user, I am constantly frustrated and misdirected by the use of javascript and event handler controlled pseudo-forms, wherein the user is presented with a menu (in the form of a listbox in GUI browsers), and is redirected to a different viewport upon selection of an OPTION. PROBLEM STATEMENT FOR POINT C: The markup behind such pseudo-forms is a mix of javascript (in particular the "function switchpage(select)" command) and HTML FORM controls, which utilize HTML4's event handler script attributes (in particular the "onchange" event handler attribute has been defined. An example (gleaned from the document source for one Web site follows: