Techniques for checkpoint 3.1 For SMIL, see specific techniques for Checkpoints 3.7, 3.8, and 3.9. Techniques for checkpoint 3.4 Provide access to a static list of time dependent links, including information about the context of the link. For example, provide the time at which the link appeared along with a way to easily jump to that portion of the presentation. Provide easy-to-use controls (including both mouse and keyboard commands) to allow viewers to pause the presentation and advance and rewind by small and large time increments. Provide a mode in which all active elements are highlighted in some way and can be navigated sequentially. For example, use a status bar to indicate the presence of active elements and allow the user to navigate among them with the keyboard or mouse to identify each element when the presentation is moving and when it is paused. Techniques for checkpoint 3.7 It is important that any continuous equivalent tracks be rendered synchronously with the primary content. This ensures that users with disabilities can use the primary and equivalent content in combination. For example, if a hard-of-hearing user is watching a video and reading captions, it is important for the captions to be in sync with the audio so that the viewer can use any residual hearing. For audio description, it is crucial that the primary audio track and the audio description track be kept in sync to avoid having them both play at once, which would reduce the clarity of the presentation. SMIL User agents which play SMIL presentations should take advantage of a variety of access features defined in SMIL. A W3C note on access features of SMIL 1.0 documents those features currently recommended [reference]. A future version of SMIL (known currently as SMIL Boston) is in development and additional access features may be available when this specification becomes a W3C Recommendation. As defined in SMIL 1.0, SMIL players should allow users to turn closed captions on and off by implementing the test attribute system-captions which takes the values "on" and "off." For example, include in the player preferences a way for users to indicate that they wish to view captions, when available. SMIL files with captions available should use the following syntax: In this case, when the user has requested captions, this textstream should be rendered, and when they have not it should not be rendered. SMIL 1.0 does not provide a test attribute to control audio description in the same way as captions. Another test attribute, system-overdub-or-captions, allows the user to choose between alternate language text or sound. This attribute specifies whether subtitles or overdub should be rendered for people who are watching a presentation where the audio may be in a language in which they are not fluent. This attribute can have two values: "overdub", which selects for substitution of one voice track for another, and "subtitle", which means that the user prefers the display of subtitles. However, this attribute should not be used to determine if users need closed captions. When both are available, deaf users will prefer to view captions, which contain additional information on music, sound effects, and who is speaking, which are not included in subtitles since those are intended for hearing people. QuickTime User agents which play QuickTime movies should provide the user with a way to turn on and off the different tracks embedded in the movie. Authors may use these alternate tracks to provide alternative equivalents for use by viewers with disabilities. The Apple QuickTime player currently provides this feature through the menu item "Enable Tracks." Microsoft Windows Media Object User agents which play Microsoft Windows Media Object presentations should provide support for Synchronized Accessible Media Interchange (SAMI), a protocol for creating and displaying caption text synchronized with a multimedia presentation. Users should be given a way to indicate their preference for viewing captions. In addition, user agents which play Microsoft Windows Media Object presentations should enable viewers to turn on and off other alternative equivalents, including audio description and alternate video tracks. Other Formats Other video or animation formats should incorporate similar features. At a minimum, users who are blind and users who are deaf need to be able to turn on and off audio description and and captions. The interface to set these preferences must be accessible. Information on how to author accessible tracks should be included in documentation about the media player. Techniques for checkpoint 3.8 Provide an interface which displays all available tracks, with as much identifying information as the author has provided, and allow users to choose which tracks are rendered. For example, if the author has provided "alt" or "title" for various tracks, use that information to construct the list of tracks. Provide an interface which allows users to indicate their preferred language separately for each kind of continuous equivalent. Users with disabilities may need to choose the language they are most familiar with in order to understand a presentation which may not include all equivalent tracks in all desired languages. In addition, international users may prefer to hear the program audio in its original language while reading captions in their first language, fulfulling the function of subtitles or to improve foreign language comprehension. In classrooms, teachers may wish to control the language of various multimedia elements to achieve specific eduational goals. Techniques for checkpoint 3.9 See specific techniques for checkpoint 3.8.