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<!DOCTYPE html PUBLIC '-//W3C//DTD HTML 4.01//EN'
'http://www.w3.org/TR/html4/strict.dtd'>
<html lang="en">
<head>
<title>CSS3 Speech Module</title>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii"/>
<link rel="stylesheet" type="text/css" href="default.css">
<style type="text/css">
.prod { font-family: inherit; font-size: inherit }
pre.prod { white-space: pre-wrap; margin: 1em 0 1em 2em }
code { font-size: inherit; }
#box-shadow-samples td { background: white; color: black; }
</style>
<style type="text/css">
/*<![CDATA[*/
caption { text-align: left; font-weight: bold }
.note { font-style: italic }
.issue { color: maroon; font-style: italic }
div.example pre { color: green; margin-left: 2em }
dl { margin-left: 2em }
caption dfn { font-size: 120% }
/*]]>*/
</style>
<link rel="stylesheet" type="text/css"
href="http://www.w3.org/StyleSheets/TR/W3C-WD.css">
</head>
<body>
<div class="head">
<!--logo-->
<h1 id="top">CSS3 Speech Module</h1>
<h2 class="no-num no-toc">[LONGSTATUS] [DATE]</h2>
<dl>
<dt>This version:
<dd><!--<a href="http://www.w3.org/TR/[YEAR]/WD-[SHORTNAME]-[CDATE]">[VERSION]</a>-->
<a href="http://dev.w3.org/csswg/css3-speech">http://dev.w3.org/csswg/css3-speech</a>
<dt>Latest version:
<dd><a
href="http://www.w3.org/TR/css3-speech">[LATEST]</a>
<dt>Previous versions:
<dd><a href="http://www.w3.org/TR/2004/WD-css3-speech-20041216/">http://www.w3.org/TR/2004/WD-css3-speech-20041216/</a>
<dt id="editors-list">Editors:
<dd><a href="mailto:dsr@w3.org">Dave Raggett</a> (<a href=
"http://www.w3.org/">W3C</a>/<a href="http://www.canon.com/">Canon</a>)</dd>
<dd><a href="mailto:daniel@glazman.org">Daniel Glazman</a> (<a href=
"http://www.disruptive-innovations.com/">Disruptive Innovations</a>)</dd>
<dd><a href="mailto:csant@opera.com">Claudio Santambrogio</a> (<a href=
"http://www.opera.com/">Opera Software</a>)</dd>
<dd><a href="mailto:dweck@daisy.org">Daniel Weck</a> (<a href=
"http://www.daisy.org">DAISY Consortium</a>)</dd>
</dl>
<!--copyright-->
<hr title="Separator for header">
</div>
<h2 id="abstract" class="no-num no-toc">Abstract</h2>
<p>CSS (Cascading Style Sheets) is a language for describing the
rendering of HTML and XML documents on screen, on paper, in speech,
etc. CSS defines aural properties that give control over rendering
XML to speech. This draft describes the text to speech properties
proposed for CSS level 3,
and is a re-work of the informative CSS2.1 Aural appendix [[CSS21]].
These are designed for match the model
described in the Speech Synthesis Markup Language (SSML) Version 1.0
[[!SPEECH-SYNTHESIS]].</p>
<p>The CSS3 Speech Module is a community effort and if you would
like to help with implementation and driving the specification
forward along the W3C Recommendation track, please contact the
editors.</p>
<h2 id="status" class="no-num no-toc">Status of this document</h2>
<!--status-->
<hr>
<p>This document is a draft of one of the "modules" for the
upcoming CSS3 specification.
<p>This document has been developed in
cooperation with the <a href="/Voice/Group/">Voice Browser working
group</a> (<a href="http://cgi.w3.org/MemberAccess/AccessRequest">W3C
Members only</a>).
<p>The following features are at-risk and may be dropped at the
end of the CR period if there has not been enough interest from
implementers: 'phoneme'
<p>The CSS WG maintains an <a href="http://www.w3.org/Style/CSS/Tracker/products/29">issues
list</a> for this module.
<h2 id="contents" class="no-num no-toc">Table of contents</h2>
<!--toc-->
<hr />
<h2 id="dependencies"><span class="secno">1. </span>Dependencies on other
modules</h2>
<p>This CSS3 module depends on the following other CSS3
modules:</p>
<ul>
<li>Cascade and Inheritance [[CSS3CASCADE]]</li>
<li>Tables [[CSS3TBL]]</li>
<li>Syntax [[CSS3SYN]]</li>
<li>Values and Units [[CSS3VAL]]</li>
</ul>
<p>It has non-normative (informative) references to the following
other CSS3 modules:</p>
<ul>
<li>The box model [[CSS3BOX]]</li>
<li>Generated and Replaced Content [[CSS3GENCON]]</li>
<li>Selectors [[SELECT]]</li>
</ul>
<h2 id="introduction"><span class="secno">2. </span>Introduction</h2>
<p>The speech rendering of a document, already commonly used by
the blind and print-impaired communities, combines speech synthesis
and "auditory icons". Often such aural presentation occurs by
converting the document to plain text and feeding this to a
<dfn>screen reader</dfn> — software or hardware that simply
reads all the characters on the screen. This results in less
effective presentation than would be the case if the document
structure were retained. Style sheet properties for text to speech
may be used together with visual properties (mixed media) or as
an aural alternative to visual presentation.</p>
<p>Besides the obvious accessibility advantages, there are other
large markets for listening to information, including in-car use,
industrial and medical documentation systems (intranets), home
entertainment, and to help users learning to read or who have
difficulty reading.</p>
<p>When using voice properties, the canvas consists of a two
channel stereo space and a temporal space (you can specify audio
cues before and after synthetic speech). The CSS properties also
allow authors to vary the characteristics of synthetic speech
(voice type, frequency, inflection, etc.).</p>
<div class="example">
<p>Examples:</p>
<pre>
h1, h2, h3, h4, h5, h6 {
voice-family: paul;
voice-stress: moderate;
cue-before: url(ping.au)
}
p.heidi { voice-balance: left; voice-family: female }
p.peter { voice-balance: right; voice-family: male }
p.goat { voice-volume: soft }
</pre>
<p>This will direct the speech synthesizer to speak headers in a
voice (a kind of "audio font") called "paul". Before speaking the
headers, a sound sample will be played from the given URL.
Paragraphs with class "heidi" will appear to come from the left
(if the sound system is capable of stereo), and paragraphs of class
"peter" from the right. Paragraphs with class "goat" will be played
softly.</p>
</div>
<h2 id="aural-model"><span class="secno">3. </span>The aural "box" model</h2>
<p>The formatting model of CSS for aural media is based on a sequence
of sounds and silences that appear in a nested model which is
related to the visual box model; however the aural canvas is one-dimensional,
monolinear. For compatibility with the visual box model, we will call
it the <dfn id="aural-box-model">aural "box" model</dfn>.</p>
<p>The element is surrounded by, in this order, 'rest', 'cue'
and 'pause' properties - they can be thought of as aural equivalents
to 'padding', 'border' and 'margin' respectively.</p>
<p>It can be represented in the following way (including the equivalent
properties from the visual box model for clarification of relationships):</p>
<p><img id="aural-box" src="aural-box.png" alt="A graph depicting the aural 'box' model."/></p>
<p>where <dfn>element</dfn> is the selected element to which the properties
from the Speech Module apply.</p>
<h2 id="mixing-props"><span class="secno">4. </span>Mixing properties:
<a href="#voice-volume">'voice-volume'</a> and
<a href="#voice-balance">'voice-balance'</a></h2>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="voice-volume">voice-volume</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><number> | <percentage> | silent | x-soft | soft |
medium | loud | x-loud | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>medium</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>yes</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>refer to inherited value</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>The 'voice-volume' refers to the amplitude of the waveform output by
the speech synthesiser. This may be mixed with other audio sources,
influencing the perceived loudness of synthetic speech relative
to these sources. Note that voice-volume does not apply to <a href
="#cue-props">audio cues</a> for which there is a separate means
to set the relative loudness.</p>
<p>Values have the following meanings:</p>
<dl>
<dt><strong><number></strong></dt>
<dd>An integer or floating point number in the range '0' to '100'.
'0' represents silence (the <em>minimum</em> level), and 100
corresponds to the <em>maximum</em> level. The volume scale is
linear amplitude.</dd>
<dt><strong><percentage></strong></dt>
<dd>Percentage values are calculated relative to the inherited
value, and are then clipped to the range '0' to '100'.</dd>
<dt><strong>silent</strong>,
<strong>x-soft</strong>,
<strong>soft</strong>,
<strong>medium</strong>,
<strong>loud</strong>, and
<strong>x-loud</strong></dt>
<dd>A sequence of monotonically non-decreasing volume levels. The value
of 'silent' is mapped to '0' and 'x-loud' is mapped to '100'.
The mapping of other values to numerical volume levels is implementation
dependent and may vary from one speech synthesizer to the next.</dd>
</dl>
<p>User agents should allow the level corresponding to '100' to be
set by the listener. No one setting is universally applicable;
suitable values depend on the equipment in use (speakers,
headphones), and the environment (in car, home theater, library)
and personal preferences.</p>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="voice-balance">voice-balance</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><number> | left | center | right | leftwards | rightwards | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>center</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>yes</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>The 'voice-balance' property refers to the balance between
left and right channels, and presumes a two channel (stereo) model
that is widely supported on consumer audio equipment.</p>
<p>Values have the following meanings:</p>
<dl>
<dt><strong><number></strong></dt>
<dd>An integer or floating point number between '-100' and '100'.
For '-100' only the left channel is audible. Simarly for '100' or
'+100' only the right channel is audible. For '0' both channels
have the same level, so that the speech appears to be coming from
the center.</dd>
<dt><strong>left</strong></dt>
<dd>Same as '-100'.</dd>
<dt><strong>center</strong></dt>
<dd>Same as '0'.</dd>
<dt><strong>right</strong></dt>
<dd>Same as '100' or '+100'.</dd>
<dt><strong>leftwards</strong></dt>
<dd>Moves the sound to the left, relative to the inherited voice
balance. More precisely, subtract 20 from the inherited value and
clip the resulting value to the range '-100' and '100'.</dd>
<dt><strong>rightwards</strong></dt>
<dd>Moves the sound to the right, relative to the inherited voice
balance. More precisely, add 20 to the inherited value and clip
the resulting value to the range '-100' and '100'.</dd>
</dl>
<p>Many speech synthesizers only support a single channel. The
voice-balance property can then be treated as part of a post
synthesis mixing step. This is where speech is mixed with other
audio sources. Note that unlike voice-volume, voice-balance
<em>does</em> apply to <a href="#cue-props">cues</a>.</p>
<h2 id="speaking-props"><span class="secno">5. </span>Speaking properties:
<a href="#speak">'speak'</a></h2>
<!-- <p>An additional speech property, speak-header, is described in the
CSS module covering tables.</p> -->
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="speak">speak</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td>none | normal | spell-out | digits | literal-punctuation |
no-punctuation | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>normal</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>yes</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>This property specifies whether text will be rendered aurally
and if so, in what manner. The possible values are:</p>
<dl>
<dt><strong>none</strong></dt>
<dd>Suppresses aural rendering so that the element requires no time
to render. Note, however, that descendants may override this value
and will be spoken. (To be sure to suppress rendering of an element
and its descendants, use the 'display' property [[CSS3BOX]]).</dd>
<dt><strong>normal</strong></dt>
<dd>Uses language-dependent pronunciation rules for rendering an
element and its children. Punctuation is not to be spoken, but
instead rendered naturally as various pauses.</dd>
<dt><strong>spell-out</strong></dt>
<dd>Spells the text one letter at a time (useful for acronyms and
abbreviations). In languages where accented characters are rare, it
is permitted to drop accents in favor of alternative unaccented
spellings. As as example, in English, the word "rôle" can
also be written as "role". A conforming implementation would thus
be able to spell-out "rôle" as "R O L E".</dd>
<dt><strong>digits</strong></dt>
<dd>Speak numbers one digit at a time, for instance, "twelve" would
be spoken as "one two", and "31" as "three one".</dd>
<dt><strong>literal-punctuation</strong></dt>
<dd>Similar to 'normal' value, but punctuation such as semicolons,
braces, and so on are to be spoken literally.</dd>
<dt><strong>no-punctuation</strong></dt>
<dd>Similar to 'normal' value but punctuation is not to be spoken
nor rendered as various pauses.</dd>
</dl>
<p>Note the difference between an element whose 'voice-volume'
property has a value of 'silent' and an element whose 'speak'
property has the value 'none'. The former takes up the same time as
if it had been spoken, including any pause before and after the
element, but no sound is generated. The latter requires no time and
is not rendered (though its descendants may be).</p>
<p>Speech synthesizers are knowledgeable about what is and what is
not a number. The speak property gives authors the means to control
h
5DC1
ow the synthesizer renders the numbers it discovers in the source
text, and may be implemented as a preprocessing step before passing
the text to the speech synthesizer.</p>
<h2 id="pause-props"><span class="secno">6. </span>Pause properties:
<a href="#pause-before">'pause-before'</a>,
<a href="#pause-after">'pause-after'</a> and
<a href="#pause">'pause'</a>,
<a href="#collapsing">collapsing pauses</a></h2>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="pause-before">pause-before</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><time> | none | x-weak | weak | medium | strong
| x-strong | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>implementation dependent</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p> </p>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="pause-after">pause-after</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><time> | none | x-weak | weak | medium | strong
| x-strong | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>implementation dependent</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>These properties specify a pause or prosodic boundary to be
observed before (or after) an element or, if any 'cue-before' or
'cue-after' is specified, before (or after) these. Values have
the following meanings:</p>
<dl>
<dt><strong><time></strong></dt>
<dd>Expresses the pause in absolute time units (seconds and
milliseconds, e.g. "3s", "250ms"). Only positive values are allowed.</dd>
<dt><strong>none</strong>,
<strong>x-weak</strong>,
<strong>weak</strong>,
<strong>medium</strong>,
<strong>strong</strong>, and
<strong>x-strong</strong>
</dt>
<dd>These values may be used to indicate the prosodic strength of
the break in speech output. The synthesis processor may insert a
pause as part of its implementation of the prosodic break. The value
"none" indicates that no prosodic break boundary should be output,
and can be used to inhibit a prosodic break which the processor
would otherwise produce. The other values indicate monotonically
non-decreasing (conceptually increasing) break strength between
elements. The stronger boundaries are typically accompanied by pauses.
"x-weak" and "x-strong" are mnemonics for "extra weak" and "extra
strong", respectively. The breaks between paragraphs are typically
much stronger than the breaks between words within a sentence.</dd>
</dl>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="pause">pause</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td>[ <'pause-before'> || <'pause-after'> ] |
inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>implementation dependent</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>The 'pause' property is a shorthand for setting 'pause-before'
and 'pause-after'. If two values are given, the first value is
'pause-before' and the second is 'pause-after'. If only one value
is given, it applies to both properties.</p>
<div class="example">
<p>Examples:</p>
<pre>
h1 { pause: 20ms } /* pause-before: 20ms; pause-after: 20ms */
h2 { pause: 30ms 40ms } /* pause-before: 30ms; pause-after: 40ms */
h3 { pause-after: 10ms } /* pause-before: <i>unspecified</i>; pause-after: 10ms */
</pre>
</div>
<h3 id="collapsing">Collapsing pauses</h3>
<p>The pause defines the minimum distance of the aural "box" to the
aural "boxes" before and after it. Adjacent pauses should be merged
by selecting the strongest named break or the longest absolute
time interval. Thus "strong" is selected when comparing "strong"
and "weak", while "1s" is selected when comparing "1s" and "250ms".
We say that such pauses <dfn id="collapse">collapse</dfn>.
A combination of a named break and time duration is treated
additively.</p>
<p>The following pauses collapse:</p>
<ol>
<li>The pause-after of an aural "box" and the pause-after of its last child,
provided the former has no rest-after and no cue-after.</li>
<li>The pause-before of an aural "box" and the pause-before of its first child,
provided the former has no rest-before and no cue-before.</li>
<li>The pause-after of an aural "box" and the pause-before of its next sibling.</li>
<li>The pause-before and pause-after of an aural "box", if the the "box" has a
voice-duration of "0ms", no rest-before or rest-after, no
cue-before or cue-after and no content.</li>
</ol>
<p>The pause-after of an element is always adjoining to the pause-before of its
next sibling.</p>
<p>The pause-before an element is adjoining to its first child's pause-before,
if the element has no cue-before nor rest-before.</p>
<p>The pause-after of an element is adjoining to its last child's pause-after,
if the element has no rest-after or cue-after.</p>
<p>An element's own pauses are adjoining if the 'voice-duration' property
is zero, and it has no rest, and it does not contain any content,
and all of its children's pauses (if any) are adjoining.</p>
<p class="note">Editor's note: 'pause' has been re-defined, and has
been moved from between the element's contents and any 'cue' to outside
the 'cue' - this is not backwards compatible with the informative CSS2.1
Aural appendix [[CSS21]].</p>
<h2 id="rest-props"><span class="secno">7. </span>Rest properties:
<a href="#rest-before">rest-before'</a>,
<a href="#rest-after">'rest-after'</a> and
<a href="#rest">'rest'</a></h2>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="rest-before">rest-before</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><time> | none | x-weak | weak | medium | strong
| x-strong | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>implementation dependent</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p> </p>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="rest-after">rest-after</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><time> | none | x-weak | weak | medium | strong
| x-strong | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>implementation dependent</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>These properties specify a rest or prosodic boundary to be observed
before (or after) speaking an element's content. Values have the following
meanings:</p>
<dl>
<dt><strong><time></strong></dt>
<dd>Expresses the rest in absolute time units (seconds and milliseconds,
e.g. "3s", "250ms"). Only positive values are allowed.</dd>
<dt><strong>none</strong>,
<strong>x-weak</strong>,
<strong>weak</strong>,
<strong>medium</strong>,
<strong>strong</strong>, and
<strong>x-strong</strong>
</dt>
<dd>These values may be used to indicate the prosodic strength of
the break in speech output. The synthesis processor may insert a
rest as part of its implementation of the prosodic break. The value
"none" indicates that no prosodic break boundary should be output,
and can be used to inhibit a prosodic break which the processor
would otherwise produce. The other values indicate monotonically
non-decreasing (conceptually increasing) break strength between words.
The stronger boundaries are typically accompanied by rests. "x-weak"
and "x-strong" are mnemonics for "extra weak" and "extra strong",
respectively.</dd>
</dl>
<p>As opposed to <a href="#pause-props">pause properties</a>, the
rest is inserted between the element's content and any 'cue-before'
or 'cue-after' content. Adjacent rests are treated additively.</p>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="rest">rest</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td>[ <'rest-before'> || <rest-after'> ] | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>implementation dependent</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>The 'rest' property is a shorthand for setting 'rest-before' and
'rest-after'. If two values are given, the first value is 'rest-before'
and the second is 'rest-after'. If only one value is given, it applies
to both properties.</p>
<h2 id="cue-props"><span class="secno">8. </span>Cue properties:
<a href="#cue-before">'cue-before'</a>,
<a href="#cue-after">'cue-after'</a> and
<a href="#cue">'cue'</a></h2>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="cue-before">cue-before</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><uri> [<number> | <percentage> | silent
| x-soft | soft | medium | loud | x-loud] | none | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>none</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>apply to inherited value for voice-volume</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p> </p>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="cue-after">cue-after</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><uri> [<number> | <percentage> | silent
| x-soft | soft | medium | loud | x-loud] | none | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>none</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>apply to inherited value for voice-volume</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>Auditory icons are another way to distinguish semantic elements.
Sounds may be played before and/or after the element to delimit it.
Values have the following meanings:</p>
<dl>
<dt><strong><uri></strong></dt>
<dd>The URI must designate an auditory icon resource. If the URI
resolves to something other than an audio file, such as an image,
the resource should be ignored and the property treated as if it
had the value 'none'.</dd>
<dt><strong>none</strong></dt>
<dd>No auditory icon is specified.</dd>
<dt><strong><number></strong></dt>
<dd>An integer or floating point number in the range '0' to '100'.
'0' represents silence (the <em>minimum</em> level), and 100
corresponds to the <em>maximum</em> level. The volume scale is
linear amplitude.</dd>
<dt><strong><percentage></strong></dt>
<dd>Percentage values are calculated relative to the inherited
value of the 'voice-volume' property, and are then clipped to
the range '0' to '100'. By basing the percentage upon the
inherited value for <a href="#mixing-props">voice-volume</a>,
it is easy to adjust the relative loudness of cues compared to
synthetic speech for whatever volume setting has been provided
for that speech.</dd>
<dt><strong>silent</strong>,
<strong>x-soft</strong>,
<strong>soft</strong>,
<strong>medium</strong>,
<strong>loud</strong>, and
<strong>x-loud</strong></dt>
<dd>A sequence of monotonically non-decreasing volume levels.
The value of 'silent' is mapped to '0' and 'x-loud' is mapped
to '100'. The mapping of other values to numerical volume levels
is implementation dependent, but the intention is to match the
corresponding levels for <a href="#mixing-props">voice-volume</a>.</dd>
</dl>
<div class="example">
<p>Examples:</p>
<pre>
a { cue-before: url(bell.aiff); cue-after: url(dong.wav) }
h1 { cue-before: url(pop.au) 80; cue-after: url(pop.au) 50% }
div.caution { cue-before: url(caution.wav) loud }
</pre>
</div>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="cue">cue</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td>[ <'cue-before'> || <'cue-after'> ] | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>not defined for shorthand properties</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>apply to inherited value for voice-volume</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>The 'cue' property is a shorthand for setting 'cue-before'
and 'cue-after'. If two values are given the first value is
'cue-before' and the second is 'cue-after'. If only one value
is given, it applies to both properties.</p>
<div class="example">
<p>The following two rules are equivalent:</p>
<pre>
h1 {cue-before: url(pop.au); cue-after: url(pop.au) }
h1 {cue: url(pop.au) }
</pre></div>
<p>If a user agent cannot render an auditory icon (e.g., the
user's environment does not permit it), we recommend that it
produce an alternative cue (e.g., popping up a warning, emitting
a warning sound, etc.)</p>
<p>Please see the sections on the ::before and ::after pseudo-elements
[[SELECT]] for information on other content
generation techniques.</p>
<!-- Add something here about gc -->
<h2 id="mark-props"><span class="secno">9. </span>Mark properties:
<a href="#mark-before">'mark-before'</a>,
<a href="#mark-after">'mark-after'</a> and
<a href="#mark">'mark'</a></h2>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="mark-before">mark-before</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><string></td>
</tr>