The Voice Browser Working Group has sought to
develop standards to enable access to the web using spoken
interaction. The Speech Synthesis Markup Language Specification is
part of this set of new markup specifications for voice browsers,
and is designed to provide a rich, XML-based markup language for
assisting the generation of synthetic speech in web and other
applications. The essential role of the markup language is to
provide authors of synthesizable content a standard way to control
aspects of speech such as pronunciation, volume, pitch, rate and
etc. across different synthesis-capable platforms.
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 working draft of the "Speech Synthesis Markup Language
Specification". You are encouraged to subscribe to the public
discussion list <www-voice@w3.org> and to mail in your comments
as soon as possible. To subscribe, send an email to <mailto:www-voice-request@w3.org>
with the word subscribe in the subject line (include the
word unsubscribe if you want to unsubscribe). A public
archive is available online.
This specification describes markup for generating synthetic
speech via a speech synthesizer, and forms part of the proposals
for the W3C Speech Interface Framework. This document has been
produced as part of the W3C
Voice Browser Activity, following the procedures set out for
the W3C
Process. The authors of this document are members of the Voice Browser Working
Group (W3C Members only).
The previous draft of this specification was published as a Last
Call Working Draft in January of 2001. Over the past year the Voice
Browser Working Group has not focused its attention on this
specification, but now it is ready to make more active and timely
progress on the specification. The Working Group has
meanwhile made progress on other specifications, such as the Speech
Recognition Grammar Format and the VoiceXML 2.0 specification.
These are related to the SSML specification, and in some areas
depend on this specification.
In order to coordinate the advancements of these specification
along the W3C track to Recommendation, the Working Group felt that
it was necessary to update the SSML specification with changes
necessary to support the VoiceXML specification. Due to changes
in the state of the art of the technology of speech synthesis during
this timeframe, the Working Group felt it would be appropriate to
make a new release of the specification, with a small number of
changes, as a Working Draft. The expectation and goal are that it
will be possible to release another draft after that one as a Last
Call Working Draft because the Working Group will have focused
sufficient attention on the specification for it to be technically
sound in today's world.
Following the publication of the previous draft of this
specification, the group received a number of public comments.
Those comments have not been addressed in this current Working
Draft but will be addressed in the timeframe of the Last Call
Working Draft. Commenters who have sent their comments to the
public mailing list need not resubmit their comments in
order for them to be addressed at that time.
To help the Voice Browser working group build an implementation
report, (as part of advancing the document on the W3C
Recommendation Track), you are encouraged to implement this
specification and to indicate to W3C which features have been
implemented, and any problems that arose.
Publication as a Working Draft does not imply endorsement by the
W3C Membership. This is a draft document and may be updated,
replaced or obsoleted by other documents at any time. It is
inappropriate to cite W3C Working Drafts as other than "work in
progress". A list of current public W3C Working Drafts can be found
at http://www.w3.org/TR/.
The W3C Standard is known as the Speech Synthesis Markup
Language specification and is based upon the JSGF and/or JSML
specifications, which are owned by Sun Microsystems, Inc.,
California, U.S.A. The JSML specification can be found at [JSML].
The Speech Synthesis Markup Language specification is part of a
larger set of markup specifications for voice browsers developed
through the open processes of the W3C. It is designed to provide a
rich, XML-based markup language for assisting the generation of
synthetic speech in web and other applications. The essential role
of the markup language is to give authors of synthesizable content
a standard way to control aspects of speech output such as
pronunciation, volume, pitch, rate and etc. across different
synthesis-capable platforms.
There is some variance in the use of technical vocabulary in the
speech synthesis community. The following definitions establish a
common understanding for this document.
| Voice Browser |
A device which interprets a (voice) markup language and is
capable of generating voice output and/or interpreting voice input,
and possibly other input/output modalities. |
| Speech Synthesis |
The process of automatic generation of speech output from data
input which may include plain text, formatted text or binary
objects. |
| Text-To-Speech |
The process of automatic generation of speech output from text
or annotated text input. |
The design and standardization process has followed from the Speech Synthesis Markup
Requirements for Voice Markup Languages published December 23,
1999 by the W3C Voice Browser Working Group.
The following items were the key design criteria.
- Consistency: provide predictable control of voice
output across platforms and across speech synthesis
implementations.
- Interoperability: support use along with other W3C
specifications including (but not limited to) the Dialog Markup
Language, Audio Cascading Style Sheets and SMIL.
- Generality: support speech output for a wide range of
applications with varied speech content.
- Internationalization: Enable speech output in a large
number of languages within or across documents.
- Generation and Readability: Support automatic
generation and hand authoring of documents. The documents should be
human-readable.
- Implementable: The specification should be
implementable with existing, generally available technology and the
number of optional features should be minimal.
A Text-To-Speech (TTS) system that supports the Speech Synthesis
Markup Language will be responsible for rendering a document as
spoken output and for using the information contained in the markup
to render the document as intended by the author.
Document creation: A text document provided as input to
the TTS system may be produced automatically, by human authoring,
or through a combination of these forms. The Speech Synthesis
markup language defines the form of the document.
Document processing: The following are the six major
processing steps undertaken by a TTS system to convert marked-up
text input into automatically generated voice output. The markup
language is designed to be sufficiently rich so as to allow control
over each of the steps described below so that the document author
(human or machine) can control the final voice output.
-
XML Parse: An XML parser is used to extract the document
tree and content from the incoming text document. The structure,
tags and attributes obtained in this step influence each of the
following steps.
-
Structure analysis: The structure of a document
influences the way in which a document should be read. For example,
there are common speaking patterns associated with paragraphs and
sentences.
- Markup support: The "paragraph" and
"sentence" elements defined in the TTS markup language
explicitly indicate document structures that affect the speech
output.
- Non-markup behavior: In documents and parts of
documents where these elements are not used, the TTS system is
responsible for inferring the structure by automated analysis of
the text, often using punctuation and other language-specific
data.
-
Text normalization: All written languages have special
constructs that require a conversion of the written form
(orthographic form) into the spoken form. Text normalization is an
automated process of the TTS system that performs this conversion.
For example, for English, when "$200" appears in a document it may
be spoken as "two hundred dollars". Similarly, "1/2" may be spoken
as "half", "January second", "February first", "one of two" and so
on.
- Markup support: The "say-as"
element can be used in the input document to explicitly
indicate the presence and type of these constructs and to resolve
ambiguities. The set of constructs that can be marked includes
dates, times, numbers, acronyms, current amounts and more. The set
covers many of the common constructs that require special treatment
across a wide number of languages but is not and cannot be a
complete set.
- Non-markup behavior: For text content that is not
marked with the "say-as" element the TTS system is expected to make
a reasonable effort to automatically locate and convert these
constructs to a speakable form. Because of inherent ambiguities
(such as the "1/2" example above) and because of the wide range of
possible constructs in any language, this process may introduce
errors in the speech output and may cause different systems to
render the same document differently.
-
Text-to-phoneme conversion: Once the system has
determined the set of words to be spoken it must convert those
words to a string of phonemes. A phoneme is the basic unit
of sound in a language. Each language (and sometimes each national
or dialect variant of a language) has a specific phoneme set: e.g.,
most US English dialects have around 45 phonemes. In many languages
this conversion is ambiguous since the same written word may have
many spoken forms. For example, in English, "read" may be spoken as
"reed" (I will read the book) or "red" (I have read the book).
Another issue is the handling of words with non-standard spellings
or pronunciations. For example, an English TTS system will often
have trouble determining how to speak some non-English-origin
names; e.g. "Tlalpachicatl" which has a Mexican/Aztec origin.
- Markup support: The "phoneme"
element allows a phonemic sequence to be provided for any word
or word sequence. This provides the content creator with explicit
control over pronunciations. The "say-as"
element may also be used to indicate that text is a proper name
that may allow a TTS system to apply special rules to determine a
pronunciation.
- Non-markup behavior: In the absence of a "phoneme" element the TTS system must apply
automated capabilities to determine pronunciations. This is
typically achieved by looking up words in a pronunciation
dictionary and applying rules to determine other pronunciations.
Most TTS systems are expert at performing text-to-phoneme
conversions so most words of most documents can be handled
automatically.
-
Prosody analysis: Prosody is the set of features of
speech output that includes the pitch (also called intonation or
melody), the timing (or rhythm), the pausing, the speaking rate,
the emphasis on words and many other features. Producing human-like
prosody is important for making speech sound natural and for
correctly conveying the meaning of spoken language.
- Markup support: The "emphasis"
element, "break" element and "prosody" element may all be used by document
creators to guide the TTS system in generating
appropriate prosodic features in the speech output.
- Non-markup behavior: In the absence of these
elements, TTS systems are expert (but not perfect) in automatically
generating suitable prosody. This is achieved through analysis of
the document structure, sentence syntax, and other information that
can be inferred from the text input.
-
Waveform production: The phonemes and prosodic
information are used by the TTS system in the production of the
audio waveform. There are many approaches to this processing step
so there may be considerable platform-specific variation.
- Markup support: The TTS markup does not provide
explicit controls over the generation of waveforms. The "voice" element allows the document creator to
request a particular voice or specific voice qualities (e.g. a
young male voice). The "audio" element allows
for insertion of recorded audio data into the output stream.
There are many classes of document creator that will produce
marked-up documents to be spoken by a TTS system. Not all document
creators (including human and machine) have access to information
that can be used in all of the elements or in each of the
processing steps described in the previous
section. The following are some of the common cases.
-
The document creator has no access to information to mark up the
text. All processing steps in the TTS system must be performed
fully automatically on raw text. The document requires
only the containing "speak" element to
indicate the content is to be spoken.
-
When marked text is generated programmatically the creator may
have specific knowledge of the structure and/or special text
constructs in some or all of the document. For example, an email
reader can mark the location of the time and date of receipt of
email. Such applications may use elements that affect structure,
text normalization, prosody and possibly text-to-phoneme
conversion.
-
Some document creators make considerable effort to mark as many
details of the document to ensure consistent speech quality across
platforms and to more precisely specify output qualities. In these
cases, the markup may use any or all of the available elements to
tightly control the speech output. For example, prompts generated
in telephony and voice browser applications may be fine-tuned to
maximize the effectiveness of the overall system.
-
The most advanced document creators may skip the higher-level
markup (structure, text normalization, text-to-phoneme conversion,
and prosody analysis) and produce low-level TTS markup for segments
of documents or for entire documents. This typically requires tools
to generate sequences of phonemes, plus pitch and timing
information. For instance, tools that do "copy synthesis" or
"prosody transplant" try to emulate human speech by copying
properties from recordings.
The following are important instances of architectures or
designs from which marked-up TTS documents will be generated. The
language design is intended to facilitate each of these
approaches.
-
Dialog language: It is a requirement that it should be
possible to include documents marked with the speech synthesis
markup language into the dialog description document to be produced
by the Voice Browser Working Group.
-
Interoperability with Aural CSS : Any
HTML processor that is Aural CSS-enabled can produce Speech
Synthesis Markup Language. ACSS is covered in Section 19 of
the Cascading Style
Sheets, level 2 (CSS2) Specification (12-May-1998). This usage
of speech synthesis facilitates improved accessibility to existing
HTML and XHTML content.
-
Application-specific style-sheet processing: As
mentioned above, there are classes of application that have
knowledge of text content to be spoken and this can be incorporated
into the speech synthesis markup to enhance rendering of the
document. In many cases, it is expected that the application will
use style-sheets to perform transformations of existing XML
documents to speech synthesis markup. This is equivalent to the use
of ACSS with HTML and once again the speech synthesis markup
language is the "final form" representation to be passed to the
speech synthesis engine. In this context, SSML may be viewed as a
superset of ACSS
capabilities, excepting spatial audio.
The Speech Synthesis Markup Language Specification provides
a standard way to specify gross properties of
synthetic speech production such as pronunciation, volume, pitch,
rate and etc. Exact specification of synthetic speech output
behavior across disparate platforms, however, is
beyond the scope of this document.
Requirements terms
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
in this document are to be interpreted as described in [RFC2119]. However, for readability, these
words do not appear in all uppercase letters in this
specification.
The following elements are defined in this draft
specification.
The Speech Synthesis Markup Language is an XML application. The
root element is speak. xml:lang is a defined attribute
specifying the language of the root document. The
version attribute is a required attribute that
indicates the version of the specification to be used for the
document. The version number for this specification is
1.0.
<?xml version="1.0"?>
<speak version="1.0" xml:lang="en-US">
... the body ...
</speak>
Following the XML
convention, languages are indicated by an xml:lang
attribute on the enclosing element with the value following [RFC3066] to define language codes. A
language is specified by an RFC 3066 identifier following the
convention of XML 1.0.
[Note: XML 1.0 adopted RFC3066 through Errata as of
2001-02-22].
Language information is inherited down the document hierarchy,
i.e. it has to be given only once if the whole document is in one
language, and language information nests, i.e. inner attributes
overwrite outer attributes.
xml:lang is a defined attribute for speak , paragraph , sentence , p , and s elements.
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xmlns="http://www.w3.org/2001/10/synthesis"
xml:lang="en-US">
<paragraph>I don't speak Japanese.</paragraph>
<paragraph xml:lang="ja">Nihongo-ga wakarimasen.</paragraph>
</speak>
General Notes (Normative)
-
The speech output platform largely determines behavior in the
case that a document requires speech output in a language not
supported by the speech output platform. In any case, if a value
for xml:lang specifying an unsupported language is
encountered, a conforming SSML processor should attempt to continue
processing and should also notify the hosting environment in that
case.
-
There may be variation across conformant platforms in the
implementation of xml:lang for different markup
elements (e.g. paragraph and sentence elements). A document
author should beware that intra-sentential language changes may not
be supported on all platforms.
-
A language change often necessitates a change in the voice.
Where the platform does not have the same voice in both the
enclosing and enclosed languages it should select a new voice with
the inherited voice attributes. Any change in voice will reset the
prosodic attributes to the default values for the new voice of the
enclosed text. Where the "xml:lang" value is the same as the
inherited value there is no need for any changes in the voice or
prosody.
-
All elements should process their contents specific to the
enclosing language. For instance, the phoneme, emphasis and break
element should each be rendered in a manner that is appropriate to
the current language.
A paragraph element represents the paragraph
structure in text. A sentence element represents the
sentence structure in text. A paragraph contains zero or more
sentences.
xml:lang is a defined attribute on both paragraph
and sentence elements.
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xmlns="http://www.w3.org/2001/10/synthesis"
xml:lang="en-US">
<paragraph>
<sentence>This is the first sentence of the paragraph.</sentence>
<sentence>Here's another sentence.</sentence>
</paragraph>
</speak>
General Notes (Normative)
-
For brevity, the markup also supports <p> and <s> as
exact equivalents of <paragraph> and <sentence>. (Note:
XML requires that the opening and closing elements be identical so
<p> text </paragraph> is not legal.). Also note that
<s> means "strike-out" in HTML 4.0 and earlier, and in
XHTML-1.0-Transitional, but not in XHTML-1.0-Strict.
-
The use of paragraph and sentence
elements is optional. Where text occurs without an enclosing
paragraph or sentence elements the speech
output system should attempt to determine the structure using
language-specific knowledge of the format of plain text.
The say-as element indicates the type of text
construct contained within the element. This information is used to
help specify the pronunciation of the contained text. Defining a
comprehensive set of text format types is difficult because of the
variety of languages that must be considered and because of the
innate flexibility of written languages. The say-as
element has been specified with a reasonable set of format types.
Text substitution may be utilized for unsupported constructs.
The type attribute is a required attribute that
indicates the contained text construct. The format is a text type
optionally followed by a colon and a format.
The base set of type values, divided according to broad
functionality, is as follows:
Pronunciation Types
-
acronym: The contained text is an acronym.
-
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
<say-as type="acronym"> DEC </say-as>
</speak>
Output: "DEC."
-
spell-out: The characters in the contained text string
are pronounced as individual characters.
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
<say-as type="spell-out"> USA </say-as>
</speak>
Output: "U, S, A".
Numerical Types
-
number: contained text contains integers,
fractions, floating points, Roman numerals or some other textual
format that can be interpreted and spoken as a number in the
current language. Format values for numbers are:
ordinal, where the contained text should be
interpreted as an ordinal. The content may be a digit sequence or
some other textual format that can be interpreted and spoken as an
ordinal in the current language; cardinal, where
the contained text should be interpreted as a cardinal. The content
may be a digit sequence or some other textual format that can be
interpreted and spoken as a cardinal in the current
language; and digits, where the contained text
is to be read as a digit sequence, rather than as a number.
-
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
Rocky <say-as type="number"> XIII </say-as>
</speak>
Output: "Rocky thirteen."
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
Pope John the <say-as type="number:ordinal"> VI </say-as>
<!-- Pope John the sixth -->
Deliver to <say-as type="number:digits"> 123 </say-as>
Brookwood.
</speak>
Output: "Deliver to one two three Brookwood."
Time, Date and Measure Types
-
date: contained text is a date. Format values for
date input content are:
"dmy", "mdy",
"ymd" (day, month , year), (month, day, year),
(year, month, day)
"ym", "my",
"md" (year, month), (month, year), (month,
day)
"y", "m", "d"
(year), (month), (day).
-
time: contained text is a time of day. Format
values for time input content are:
"hms", "hm",
"h" (hours, minutes, seconds), (hours, minutes),
(hours).
-
duration: contained text is a temporal duration.
Format values for duration input content are:
"hms", "hm",
"ms", "h", "m",
"s" (hours, minutes, seconds), (hours, minutes),
(minutes, seconds), (hours), (minutes), (seconds).
-
currency: contained text is a currency amount.
-
measure: contained text is a measurement.
-
telephone: contained text is a telephone
number.
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
<say-as type="date:ymd"> 2000/1/20 </say-as>
<!-- January 20th two thousand -->
Proposals are due in <say-as type="date:my"> 5/2001 </say-as>
<!-- Proposals are due in May two thousand and one -->
The total is <say-as type="currency">$20.45</say-as>
<!-- The total is twenty dollars and forty-five cents -->
</speak>
Address, Name, Net Types
-
name: contained text is a proper name of a person,
company etc.
-
net: contained text is an internet identifier.
Format values for internet identifier input content are:
"email", "uri".
-
address: contained text is a postal address.
-
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
<say-as type="net:email"> road.runner@acme.com </say-as>
</speak>
General Notes (Normative)
-
When specified, format values of say-as attributes
are to be interpreted by the conforming SSML processor as hints
provided by the mark-up document author to aide text normalization
and pronunciation.
-
In all cases, the text enclosed by any say-as
element is intended to be a standard, orthographic form of the
language currently in context. An SSML processor should be able to
support the common, orthographic forms of the specified language.
In the case of dates for example, <say-as type="date">
2000/1/20 </say-as> may be read as "January twentieth two
thousand" or as "the twentieth of January two thousand" and so
on.
-
When character(s) designating currency units are included in the
enclosed text, the SSML processor should include the units in the
rendered output.
Usage Notes (Informative)
-
When multi-field quantities are specified in the format value
attribute ("dmy", "my", etc.), the processor may assume that the
fields are separated by a single, non-alphanumeric character. The
resulting orthographic form may be language-specific, e.g. using a
slash to delimit year, month and day in English.
The phoneme element provides a phonetic
pronunciation for the contained text. The
"phoneme" element may be empty. However, it is
recommended that the element contain human-readable text that can
be used for non-spoken rendering of the document. For example, the
content may be displayed visually for users with hearing
impairments.
The ph attribute is a required attribute that
specifies the phoneme string.
The alphabet attribute is an optional attribute
that specifies the phonetic alphabet. The default value of
alphabet for a conforming SSML processor is
"ipa", corresponding to characters composing the
International Phonetic Alphabet. In addition to an exhaustive set
of vowel and consonant symbols, IPA supports a syllable delimiter,
numerous diacritics, stress symbols, lexical tone symbols,
intonational markers and more.
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
<phoneme alphabet="ipa" ph="tɒmɑtoʊ">
tomato
</phoneme>
<!-- This is an example of IPA using character entities -->
</speak>
If a value for alphabet specifying an unknown
phonetic alphabet is encountered, a conforming SSML processor
should continue processing and should notify the hosting
environment in that case.
Usage Notes (Informative)
-
Characters composing many of the International Phonetic Alphabet
(IPA) phonemes are known to display improperly on most platforms.
Additional IPA limitations include the fact that IPA is difficult
to understand even when using ASCII equivalents, IPA is missing
symbols required for many of the world's languages, and IPA editors
and fonts containing IPA characters are not widely available. The
Voice Browser Working Group will address the issue of specifying a
more robust phoneme alphabet at a later date.
-
Entity definitions may be used for repeated pronunciations. For
example:
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE speak PUBLIC "-//W3C//DTD SYNTHESIS 1.0//EN"
"http://www.w3.org/TR/speech-synthesis/synthesis.dtd"
[
<!ENTITY uk_tomato "tɒmɑtoʊ">
]>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
... you say <phoneme ph="&uk_tomato;"> tomato </phoneme>
I say...
</speak>
The sub element is employed to indicate that the
specified text replaces the contained text for pronunciation. This
allows a document to contain both a spoken and written form. The
required alias attribute specifies the string to be
substituted for the enclosed string.
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
<sub alias="World Wide Web Consortium"> W3C </sub>
<!-- World Wide Web Consortium -->
</speak>
The "voice" element is a production element
that requests a change in speaking voice. Attributes are:
-
xml:lang: optional language specification
attribute.
-
gender: optional attribute indicating the preferred
gender of the voice to speak the contained text. Enumerated values
are: "male", "female", "neutral".
-
age: optional attribute indicating the preferred
age of the voice to speak the contained text. Acceptable values are
of type (integer)
-
variant: optional attribute indicating a preferred
variant of the other voice characteristics to speak the contained
text. (e.g. the second or next male child voice). Valid values of
variant are integers.
-
name: optional attribute indicating a
platform-specific voice name to speak the contained text. The value
may be a space-separated list of names ordered from top preference
down.
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
<voice gender="female">Mary had a little lamb,</voice>
<!-- now request a different female child's voice -->
<voice gender="female" variant="2">
It's fleece was white as snow.
</voice>
<!-- platform-specific voice selection -->
<voice name="Mike">I want to be like Mike.</voice>
</speak>
General Notes (Normative)
-
When there is not a voice available that exactly matches the
attributes specified in the document, or multiple voices that match
the criteria, the voice selection algorithm may be
platform-specific. In both cases, a conforming SSML processor
should continue processing and should notify the hosting
environment.
-
Voice attributes are inherited down the tree including to within
elements that change the language.
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
<voice gender="female">
Any female voice here.
<voice age="6">
A female child voice here.
<paragraph xml:lang="ja">
<!-- A female child voice in Japanese. -->
</paragraph>
</voice>
</voice>
</speak>
-
A change in voice resets the prosodic parameters since different
voices have different natural pitch and speaking rates. Volume is
the only exception.
-
The xml:lang attribute may be used specially to
request usage of a voice with a specific dialect or other variant
of the enclosing language.
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
<voice xml:lang="en-cockney">
Try a Cockney voice (London area).
</voice>
<voice xml:lang="en-brooklyn">
Try one with a New York accent.
</voice>
</speak>
The "emphasis" element requests that the
contained text be spoken with emphasis (also referred to as
prominence or stress). The synthesizer determines how to render
emphasis since the nature of emphasis differs between languages,
dialects or even voices. The attributes are:
-
level: the level attribute indicates
the strength of emphasis to be applied. Defined values are
"strong", "moderate",
"none" and "reduced". The default
level is "moderate". The meaning of
"strong" and "moderate" emphasis
is interpreted according to the language being spoken (languages
indicate emphasis using a possible combination of pitch change,
timing changes, loudness and other acoustic differences). The
"reduced" level is effectively the opposite of
emphasizing a word. For example, when the phrase "going to" is
reduced it may be spoken as "gonna". The "none"
level is used to prevent the speech synthesizer from emphasizing
words that it might typically emphasize.
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
That is a <emphasis> big </emphasis> car!
That is a <emphasis level="strong"> huge </emphasis>
bank account!
</speak>
The break element is an empty element that controls
the pausing or other prosodic boundaries between words. The use of
the break element between any pair of words is optional. If the
element is not defined, the speech synthesizer is expected to
automatically determine a break based on the linguistic context. In
practice, the break element is most often used to
override the typical automatic behavior of a speech synthesizer.
The attributes are:
-
size: the size attribute is an
optional attribute having one of the following relative values:
"none", "small",
"medium" (default value), or
"large". The value "none"
indicates that a normal break boundary should be used. The other
three values indicate increasingly large break boundaries between
words. The larger boundaries are typically accompanied by
pauses.
-
time: the time attribute is an
optional attribute indicating the duration of a pause in seconds or
milliseconds. It follows the "Times" attribute format from the Cascading Style Sheets,
level 2 (CSS2) Specification . e.g. "250ms", "3s".
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
Take a deep breath <break/> then continue.
Press 1 or wait for the tone. <break time="3s"/>
I didn't hear you!
</speak>
Usage Notes (Informative)
-
Using the size attribute is generally preferable to
the time attribute within normal speech. This is
because the speech synthesizer will modify the properties of the
break according to the speaking rate, voice and possibly other
factors. As an example, a fixed 250ms pause (placed with the
time attribute) sounds much longer in fast speech than
in slow speech.
The prosody element permits control of the pitch,
speaking rate and volume of the speech output. The attributes
are:
-
pitch: the baseline pitch for the contained text in
Hertz, a relative change or values "high",
"medium", "low",
"default".
-
contour: sets the actual pitch contour for the
contained text. The format is outlined below.
-
range: the pitch range (variability) for the
contained text in Hertz, a relative change or values
"high", "medium",
"low", "default".
-
rate: the speaking rate in words-per-minute for the
contained text, a relative change or values
"fast", "medium",
"slow", "default".
-
duration: a value in seconds or milliseconds for
the desired time to take to read the element contents. Follows the
Times attribute format from the Cascading Style Sheets, level
2 (CSS2) Specification . e.g. "250ms", "3s".
-
volume: the volume for the contained text in the
range 0.0 to 100.0 (higher values are louder and specifying a value
of zero is equivalent to specifying "silent"), a
relative change or values "silent",
"soft", "medium",
"loud" or "default".
Relative values
Relative changes for any of the attributes above are specified
as floating-point values: "+10", "-5.5", "+15.2%", "-8.0%". For the
pitch and range attributes, relative changes in semitones are
permitted: "+0.5st", "+5st", "-2st".
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
The price of XYZ is <prosody rate="-10%">
<say-as type="currency">$45</say-as></prosody>
</speak>
Pitch contour
The pitch contour is defined as a set of targets at specified
intervals in the speech output. The algorithm for interpolating
between the targets is platform-specific. In each pair of the form
(interval,target), the first value is a percentage of
the period of the contained text and the second value is the value
of the pitch attribute (absolute, relative, relative
semitone, or descriptive values are all permitted). Interval values
outside 0% to 100% are ignored. If a value is not defined for 0% or
100% then the nearest pitch target is copied.
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xml:lang="en-US"
xmlns="http://www.w3.org/2001/10/synthesis">
<prosody contour="(0%,+20)(10%,+30%)(40%,+10)">
good morning
</prosody>
</speak>
General Notes (Normative)
-
The duration attribute takes precedence over the
rate attribute. The contour attribute
takes precedence over the pitch and range
attributes.
-
All prosodic attribute values are indicative. If a conforming
speech synthesizer is unable to accurately render a document as
specified, (e.g. trying to set the pitch to 1Mhz, or the speaking
rate to 1,000,000 words per minute.) it will make a best effort to
continue processing by imposing a limit or a substitute for the
specified, unsupported value.
-
In some cases, SSML processors may elect to ignore a given
prosodic markup if the processor determines, for
example, that the indicated value is redundant, improper or in
error. In particular, concatenative-type synthetic speech systems
that employ large acoustic units may reject prosody-modifying
markup elements if they are redundant with the prosody of a given
acoustic unit(s) or would otherwise result in degraded speech
quality.
-
The default value of all prosodic attributes is no change. For
example, omitting the rate attribute means that the
rate is the same within the element as outside.
Usage Notes (Informative)
-
The descriptive values ("high", "medium" etc.) may be specific
to the platform, to user preferences or to the current language and
voice. As such, it is generally preferable to use the descriptive
values or the relative changes over absolute values.
The audio element supports the insertion of recorded audio files and the insertion of other
audio formats in conjunction with synthesized speech output. The
audio element may be empty. If the audio
element is not empty then the contents should be the marked-up text
to be spoken if the audio document is not available. The alternate
content may include text, speech markup, or another
audio element. The alternate contents may also be used
when rendering the document to non-audible output and for
accessibility. The optional attribute is src, which is
the URI of a document with an appropriate mime-type.
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xmlns="http://www.w3.org/2001/10/synthesis"
xml:lang="en-US">
<!-- Empty element -->
Please say your name after the tone. <audio src="beep.wav"/>
<!-- Container element with alternative text -->
<audio src="prompt.au">What city do you want to fly from?</audio>
<audio src="welcome.wav">
<emphasis>Welcome</emphasis> to the Voice Portal.
</audio>
</speak>
An audio element is sucessfully rendered if:
- The referenced audio source is played, or
- If the processor is unable to execute #1, then the alternative
content is successfully rendered.
Deciding which conditions result in the alternative content
being rendered is platform dependent. If the audio
element is not successfully rendered, a conforming SSML processor
should continue processing and should notify the hosting
environment in that case. An SSML processor may determine after
beginning playback of an audio source that it cannot be played in
its entirety. For example, encoding problems, network disruptions,
etc. may occur. The processor may designate this either as
successful or unsuccessful rendering, but it must document this
behavior.
Usage Notes (Informative)
A mark element is an element that places a marker
into the text/tag sequence. The mark element that
contains text is used to reference a special sequence of tags and
text, either for internal reference within the SSML document, or
externally by another document. The empty mark element
can also be used to reference a specific location in the text/tag
sequence, and can additionally be used to insert a marker into an
output stream for asynchronous notification. When audio output of
the TTS document reaches the mark, the speech
synthesizer issues an event that includes the required
name attribute of the element. The platform defines
the destination of the event. The mark element does
not affect the speech output process.
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xmlns="http://www.w3.org/2001/10/synthesis"
xml:lang="en-US">
We would like
<mark name="congrats">to extend our warmest congratulations</mark>
to the members of the Voice Browser Working Group!
Go from <mark name="here"/> here, to <mark name="there"/> there!
</speak>
Usage Notes (Informative)
When supported by the implementation, requests can be made to
pause and resume at document locations specified by the
mark values.
A legal Speech Synthesis Markup Language document must have a
legal XML
Prolog [XML §2.8].
The XML prolog in a synthesis document comprises the XML
declaration and an optional DOCTYPE declaration referencing the
synthesis DTD. It is followed by the root speak
element. The XML prolog may also contain XML comments, processor
instructions and other content permitted by XML in a prolog.
The version number of the XML declaration indicates which
version of XML is being used. The version number of the
speak element indicates which version of the SSML
specification is being used -- "1.0" for this
specification. The speak version is a
required attribute.
The speak element must designate the SSML namespace
using the xmlns attribute [XMLNS]. The
namespace for SSML is defined to be http://www.w3.org/2001/10/synthesis.
If present, the DOCTYPE should reference the standard DOCTYPE
and identifier.
The following are two examples of SSML headers:
<?xml version="1.0" encoding="ISO-8859-1"?>
<speak version="1.0" xmlns="http://www.w3.org/2001/10/synthesis"
xml:lang="en">
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE speak PUBLIC "-//W3C//DTD SYNTHESIS 1.0//EN"
"http://www.w3.org/TR/speech-synthesis/synthesis.dtd">
<speak version="1.0" xmlns="http://www.w3.org/2001/10/synthesis"
xml:lang="en">
The Synchronized
Multimedia Integration Language (SMIL, pronounced "smile")
enables simple authoring of interactive audiovisual presentations.
SMIL is typically used for "rich media"/multimedia presentations
which integrate streaming audio and video with images, text or any
other media type. SMIL
is an easy-to-learn HTML-like language, and many SMIL presentations are
written using a simple text-editor. See the SMIL/SSML integration
examples in Appendix A..
Aural style
sheets are employed to augment standard visual forms of
documents (like HTML) with additional elements that assist in the
synthesis of the text into audio. In comparison to SSML,
ACSS-generated documents are capable of more complex specifications
of the audio sequence, including the designation of 3D location of
the audio source. Many of the other ACSS elements
overlap SSML functionality, especially in the specification of
voice type/quality. SSML may be viewed as a superset of ACSS
capabilities, excepting spatial audio.
The fetching and caching behavior of SSML documents is defined
by the environment in which the SSML processor operates. In a
VoiceXML interpreter context for example, the caching policy is
determined by the VoiceXML interpreter.
This section is Normative.
A synthesis document fragment is a Conforming Speech
Synthesis Markup Language Fragment if:
- it is a well-formed
XML document [XML] conforming
to namespaces in XML [XMLNS]
- and it conforms to the criteria for Conforming Stand-Alone Speech Synthesis Markup
Language Documents after:
- all non-synthesis namespace elements and attributes and all
xmlns attributes which refer to non-synthesis namespace elements
are removed from the document,
- and, an appropriate XML declaration (i.e.,
<?xml...?>) is included at the top of the
document,
- and, if the
speak element does not already
designate the synthesis namespace using the "xmlns" attribute, then
xmlns="http://www.w3.org/2001/10/synthesis" is added
to the element.
A document is a Conforming Stand-Alone Speech
Synthesis Markup Language Document if:
The Speech Synthesis specification and these conformance
criteria provide no designated size limits on any aspect of
synthesis documents. There are no maximum values on
the number of elements, the amount of character data, or the number
of characters in attribute values.
The SSML namespace may be used with other XML namespaces as per
the Namespaces
in XML Recommendation. Future work by W3C will address ways to
specify conformance for documents involving multiple
namespaces.
-
A Speech Synthesis Markup Language processor is a program that
can parse and process Speech Synthesis Markup Language documents.
-
In a Conforming Speech Synthesis Markup Language Processor, the
XML parser must be able to parse and process all XML constructs
defined within XML 1.0
and XML
Namespaces.
-
A Conforming Speech Synthesis Markup Language Processor must
correctly understand and apply the semantics defined for each
markup element as described by this document.
-
A Conforming Speech Synthesis Markup Language Processor is
required to parse all language declarations successfully.
-
A Conforming Speech Synthesis Markup Language Processor should
inform its hosting environment if it encounters a language that it
can not support.
-
There is no conformance requirement with respect to performance
characteristics of the Speech Synthesis Markup Language
Processor.
5.1 Normative References
- [XML]
- World Wide Web Consortium. Extensible Markup Language (XML)
1.0 (Second Edition). W3C Recommendation, 6 October 2000. See
http://www.w3.org/TR/2000/REC-xml-20001006
- [XMLNS]
- World Wide Web Consortium. Namespaces in XML. W3C
Recommendation. See http://www.w3.org/TR/REC-xml-names
- [JSML]
- Sun Microsystems. JSpeech Markup
Language. Sun Microsystems submission to W3C, 5
June 2000. See http://www.w3.org/TR/jsml/
- [RFC2119]
- S. Bradner, Key words for use in RFCs to Indicate
Requirement Levels , Harvard University, March 1997.
See http://www.normos.org/ietf/rfc/rfc2119.txt
- [RFC3066]
- H. Alvestrand, Tags for the Identification of
Languages. See http://www.ietf.org/rfc/rfc3066.txt
- [CSS2]
- World Wide Web Consortium, Cascading Style Sheets,
level 2 CSS2 Specification. W3C Recommendation.
See http://www.w3.org/TR/REC-CSS2/aural.html
- [VXML]
- World Wide Web Consortium. Voice Extensible Markup
Language (VoiceXML) Version 2.0. W3C Working Draft.
See http://www.w3.org/TR/2001/WD-voicexml20-20011023/
5.2 Informative References
- [SABLE]
- R. Sproat, SABLE. A Standard for TTS Markup. See
http://www.research.att.com/~rws/Sable.v1_0.htm
This document was written with the participation of the members
of the W3C Voice Browser Working Group (listed in alphabetical
order):
- Brian Eberman, SpeechWorks International
Andrew Hunt, SpeechWorks International
Jim Larson, Intel
Bruce Lucas, IBM
Scott McGlashan, PipeBeach
T.V. Raman, IBM
Dave Raggett, W3C/Openwave
Richard Sproat, ATT
Luc Van Tichelen, ScanSoft
Kuansan Wang, Microsoft
Mark Walker, Intel
This appendix is Non-Normative.
The following is an example of reading headers of email
messages. The paragraph and sentence elements
are used to mark the text structure. The say-as
element is used to indicate text constructs such as the time
and proper name. The break element is placed
before the time and has the effect of marking the time as important
information for the listener to pay attention to. The prosody element is used to slow the speaking rate
of the email subject so that the user has extra time to listen and
write down the details.
<?xml version="1.0"?>
<speak xmlns="http://www.w3.org/2001/10/synthesis" xml:lang="en">
<paragraph>
<sentence>You have 4 new messages.</sentence>
<sentence>The first is from
<say-as type="name">
Stephanie Williams
</say-as>
and arrived at <break/>
<say-as type="time">3:45pm</say-as>.
</sentence>
<sentence>
The subject is <prosody rate="-20%">ski trip</prosody>
</sentence>
</paragraph>
</speak>
The following example combines audio files and different spoken
voices to provide information on a collection of music.
<?xml version="1.0"?>
<speak xmlns="http://www.w3.org/2001/10/synthesis" xml:lang="en">
<paragraph>
<voice gender="male">
<sentence>Today we preview the latest romantic music
from the W3C.</sentence>
<sentence>Hear what the Software Reviews said about
Tim Lee's newest hit.</sentence>
</voice>
</paragraph>
<paragraph>
<voice gender="female">
He sings about issues that touch us all.
</voice>
</paragraph>
<paragraph>
<voice gender="male">
Here's a sample. <audio src="http://www.w3c.org/music.wav"/>
Would you like to buy it?
</voice>
</paragraph>
</speak>
SMIL Integration Example
The SMIL language is an XML-based multimedia control language.
It is especially well suited for describing dynamic media
applications that include synthetic speech output.
File 'greetings.ssml' contains the
following:
<?xml version="1.0"?>
<speak xmlns="http://www.w3.org/2001/10/synthesis" xml:lang="en">
<sentence>
<mark name="greetings">
<emphasis>Greetings</emphasis> from the
<sub alias="World Wide Web Consortium">W3C</sub>!
</mark>
</sentence>
</speak>
SMIL Example 1: W3C logo image appears, and then one
second later, the speech sequence is rendered. File
'greetings.smil' contains the following:
<smil xmlns="http://www.w3.org/2001/SMIL20/Language">
<head>
<top-layout width="640" height="320">
<region id="whole" width="640" height="320"/>
</top-layout>
</head>
<body>
<par>
<img src="http://w3clogo.gif" region="whole" begin="0s"/>
<ref src="greetings.ssml#greetings" begin="1s"/>
</par>
</body>
</smil>
SMIL Example 2: W3C logo image appears, then clicking
on the image causes it to disappear and the speach sequence to be
rendered. File 'greetings.smil' contains the following:
<smil xmlns="http://www.w3.org/2001/SMIL20/Language">
<head>
<top-layout width="640" height="320">
<region id="whole" width="640" height="320"/>
</top-layout>
</head>
<body>
<seq>
<img id="logo" src="http://w3clogo.gif" region="whole"
begin="0s" end="logo.activateEvent"/>
<ref src="greetings.ssml#greetings"/>
</seq>
</body>
</smil>
This appendix is Informative.
The synthesis DTD is located at http://www.w3.org/TR/speech-synthesis/synthesis.dtd.
<?xml version="1.0" encoding="ISO-8859-1"?>
<!--
SSML DTD 20020313
Copyright 1998-2002 W3C (MIT, INRIA, Keio), All Rights Reserved.
Permission to use, copy, modify and distribute the SSML DTD and
its accompanying documentation for any purpose and without fee is
hereby granted in perpetuity, provided that the above copyright
notice and this paragraph appear in all copies.
The copyright holders make no representation about the suitability
of the DTD for any purpose. It is provided "as is" without expressed
or implied warranty.
-->
<!ENTITY % duration "CDATA">
<!ENTITY % integer "CDATA">
<!ENTITY % uri "CDATA">
<!ENTITY % audio "#PCDATA | audio ">
<!ENTITY % structure "paragraph | p | sentence | s">
<!ENTITY % sentence-elements "break | emphasis | mark | phoneme |
prosody | say-as | voice | sub">
<!ENTITY % allowed-within-sentence " %audio; | %sentence-elements; ">
<!ENTITY % say-as-types "(acronym|spell-out|currency|measure|
name|telephone|address|
number|number:ordinal|number:digits|number:cardinal|
date|date:dmy|date:mdy|date:ymd|
date:ym|date:my|date:md|
date:y|date:m|date:d|
time|time:hms|time:hm|time:h|
duration|duration:hms|duration:hm|duration:ms|
duration:h|duration:m|duration:s|
net|net:email|net:uri)">
<!ELEMENT speak (%allowed-within-sentence; | %structure;)*>
<!ATTLIST speak
version NMTOKEN #REQUIRED
xml:lang NMTOKEN #IMPLIED
xmlns CDATA #REQUIRED
xmlns:xsi CDATA #IMPLIED
xsi:schemaLocation CDATA #IMPLIED
>
<!ELEMENT paragraph (%allowed-within-sentence; | sentence | s)*>
<!ATTLIST paragraph
xml:lang NMTOKEN #IMPLIED
>
<!ELEMENT sentence (%allowed-within-sentence;)*>
<!ATTLIST sentence
xml:lang NMTOKEN #IMPLIED
>
<!ELEMENT p (%allowed-within-sentence; | sentence | s)*>
<!ATTLIST p
xml:lang NMTOKEN #IMPLIED
>
<!ELEMENT s (%allowed-within-sentence;)*>
<!ATTLIST s
xml:lang NMTOKEN #IMPLIED
>
<!ELEMENT voice (%allowed-within-sentence; | %structure;)*>
<!ATTLIST voice
xml:lang NMTOKEN #IMPLIED
gender (male | female | neutral) #IMPLIED
age %integer; #IMPLIED
variant %integer; #IMPLIED
name CDATA #IMPLIED
>
<!ELEMENT prosody (%allowed-within-sentence; | %structure;)*>
<!ATTLIST prosody
pitch CDATA #IMPLIED
contour CDATA #IMPLIED
range CDATA #IMPLIED
rate CDATA #IMPLIED
duration %duration; #IMPLIED
volume CDATA #IMPLIED
>
<!ELEMENT audio (%allowed-within-sentence; | %structure;)*>
<!ATTLIST audio
src %uri; #IMPLIED
>
<!ELEMENT emphasis (%allowed-within-sentence;)*>
<!ATTLIST emphasis
level (strong | moderate | none | reduced) "moderate"
>
<!ELEMENT say-as (#PCDATA)>
<!ATTLIST say-as
type %say-as-types; #REQUIRED
>
<!ELEMENT sub (#PCDATA)>
<!ATTLIST sub
alias CDATA #REQUIRED
>
<!ELEMENT phoneme (#PCDATA)>
<!ATTLIST phoneme
ph CDATA #REQUIRED
alphabet CDATA "ipa"
>
<!ELEMENT break EMPTY>
<!ATTLIST break
size (large | medium | small | none) "medium"
time %duration; #IMPLIED
>
<!ELEMENT mark (%allowed-within-sentence; | %structure;)*>
<!ATTLIST mark
name ID #REQUIRED
>
This appendix is Normative.
The synthesis schema is located at http://www.w3.org/TR/speech-synthesis/synthesis.xsd.
Note: the synthesis schema includes a no-namespace core
schema, located at http://www.w3.org/TR/speech-synthesis/synthesis-core.xsd,
which may be used as a basis for specifying Speech Synthesis Markup
Language Fragments embedded in non-synthesis namespace
schemas.
<?xml version="1.0" encoding="ISO-8859-1"?>
<xsd:schema targetNamespace="http://www.w3.org/2001/10/synthesis"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns="http://www.w3.org/2001/10/synthesis"
elementFormDefault="qualified">
<xsd:annotation>
<xsd:documentation>SSML 1.0 Schema (20020311)</xsd:documentation>
</xsd:annotation>
<xsd:annotation>
<xsd:documentation>Copyright 1998-2002 W3C (MIT, INRIA, Keio),
All Rights Reserved. Permission to use, copy, modify and
distribute the SSML schema and its accompanying documentation
for any purpose and without fee is hereby granted in
perpetuity, provided that the above copyright notice and this
paragraph appear in all copies. The copyright holders make no
representation about the suitability of the schema for any purpose.
It is provided "as is" without expressed or implied warranty.
</xsd:documentation>
</xsd:annotation>
<xsd:include schemaLocation="synthesis-core.xsd"/>
</xsd:schema>
<?xml version="1.0" encoding="ISO-8859-1"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified">
<xsd:annotation>
<xsd:documentation>SSML 1.0 Core Schema
(20020222)</xsd:documentation>
</xsd:annotation>
<xsd:annotation>
<xsd:documentation>Copyright 1998-2002 W3C (MIT,
INRIA, Keio), All Rights Reserved. Permission to use,
copy, modify and distribute the SSML core schema and its
accompanying documentation for any purpose and without
fee is hereby granted in perpetuity, provided that the
above copyright notice and this paragraph appear in all
copies. The copyright holders make no representation
about the suitability of the schema for any purpose.
It is provided "as is" without expressed or implied
warranty.</xsd:documentation>
</xsd:annotation>
<xsd:annotation>
<xsd:documentation>Importing dependent
namespaces</xsd:documentation>
</xsd:annotation>
<xsd:import namespace="http://www.w3.org/XML/1998/namespace"
schemaLocation="http://www.w3.org/2001/xml.xsd"/>
<xsd:annotation>
<xsd:documentation>General Datatypes</xsd:documentation>
</xsd:annotation>
<xsd:simpleType name="duration">
<xsd:annotation>
<xsd:documentation>Duration follows "Times" in
CCS specification; e.g. "25ms", "3s"</xsd:documentation>
</xsd:annotation>
<xsd:restriction base="xsd:string">
<xsd:pattern value="[0-9]+m?s"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:simpleType name="relative.change">
<xsd:annotation>
<xsd:documentation>Relative change: e.g. +10, -5.5,
+15%, -9.0%</xsd:documentation>
</xsd:annotation>
<xsd:restriction base="xsd:string">
<xsd:pattern value="[+-][0-9]+(.[0-9]+)?[%]?"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:simpleType name="relative.change.st">
<xsd:annotation>
<xsd:documentation>Relative change in semi-tones:
e.g. +10st, -5st</xsd:documentation>
</xsd:annotation>
<xsd:restriction base="xsd:string">
<xsd:pattern value="[+-]?[0-9]+st"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:simpleType name="height.scale">
<xsd:annotation>
<xsd:documentation>values for height
</xsd:documentation>
</xsd:annotation>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="high"/>
<xsd:enumeration value="medium"/>
<xsd:enumeration value="low"/>
<xsd:enumeration value="default"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:simpleType name="number.range">
<xsd:annotation>
<xsd:documentation>number range: e.g. 0-123, 23343-223333.
No constraint that the second number is greater than the first.
</xsd:documentation>
</xsd:annotation>
<xsd:restriction base="xsd:string">
<xsd:pattern value="[0-9]+-.[0-9]+"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:simpleType name="speed.scale">
<xsd:annotation>
<xsd:documentation>values for speed
</xsd:documentation>
</xsd:annotation>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="fast"/>
<xsd:enumeration value="medium"/>
<xsd:enumeration value="slow"/>
<xsd:enumeration value="default"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:simpleType name="volume.scale">
<xsd:annotation>
<xsd:documentation>values for speed
</xsd:documentation>
</xsd:annotation>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="silent"/>
<xsd:enumeration value="soft"/>
<xsd:enumeration value="medium"/>
<xsd:enumeration value="loud"/>
<xsd:enumeration value="default"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:simpleType name="float.range1">
<xsd:annotation>
<xsd:documentation>0.0 - 100.0
</xsd:documentation>
</xsd:annotation>
<xsd:restriction base="xsd:float">
<xsd:minInclusive value="0.0"/>
<xsd:maxInclusive value="100.0"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:simpleType name="Say-as.datatype">
<xsd:annotation>
<xsd:documentation>say-as datatypes
</xsd:documentation>
</xsd:annotation>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="acronym"/>
<xsd:enumeration value="spell-out"/>
<xsd:enumeration value="number"/>
<xsd:enumeration value="number:ordinal"/>
<xsd:enumeration value="number:digits"/>
<xsd:enumeration value="number:cardinal"/>
<xsd:enumeration value="date"/>
<xsd:enumeration value="date:dmy"/>
<xsd:enumeration value="date:mdy"/>
<xsd:enumeration value="date:ymd"/>
<xsd:enumeration value="date:ym"/>
<xsd:enumeration value="date:my"/>
<xsd:enumeration value="date:md"/>
<xsd:enumeration value="date:y"/>
<xsd:enumeration value="date:m"/>
<xsd:enumeration value="date:d"/>
<xsd:enumeration value="time"/>
<xsd:enumeration value="time:hms"/>
<xsd:enumeration value="time:hm"/>
<xsd:enumeration value="time:h"/>
<xsd:enumeration value="duration"/>
<xsd:enumeration value="duration:hms"/>
<xsd:enumeration value="duration:hm"/>
<xsd:enumeration value="duration:ms"/>
<xsd:enumeration value="duration:h"/>
<xsd:enumeration value="duration:m"/>
<xsd:enumeration value="duration:s"/>
<xsd:enumeration value="currency"/>
<xsd:enumeration value="measure"/>
<xsd:enumeration value="name"/>
<xsd:enumeration value="net"/>
<xsd:enumeration value="net:email"/>
<xsd:enumeration value="net:uri"/>
<xsd:enumeration value="address"/>
<xsd:enumeration value="telephone"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:annotation>
<xsd:documentation>General attributes</xsd:documentation>
</xsd:annotation>
<xsd:annotation>
<xsd:documentation>Elements</xsd:documentation>
</xsd:annotation>
<xsd:element name="aws" abstract="true">
<xsd:annotation>
<xsd:documentation>The 'allowed-within-sentence'
group uses this abstract element. Elements with aws as
their substitution class are then alternatives for
'allowed-within-sentence'.</xsd:documentation>
</xsd:annotation>
</xsd:element>
<xsd:group name="allowed-within-sentence">
<xsd:choice>
<xsd:element ref="aws"/>
</xsd:choice>
</xsd:group>
<xsd:element name="struct" abstract="true"/>
<xsd:group name="structure">
<xsd:choice>
<xsd:element ref="struct"/>
</xsd:choice>
</xsd:group>
<xsd:element name="speak" type="speak"/>
<xsd:complexType name="speak" mixed="true">
<xsd:choice minOccurs="0" maxOccurs="unbounded">
<xsd:group ref="allowed-within-sentence"/>
<xsd:group ref="structure"/>
</xsd:choice>
<xsd:attribute name="version" use="required">
<xsd:simpleType>
<xsd:restriction base="xsd:NMTOKEN"/>
</xsd:simpleType>
</xsd:attribute>
<xsd:attribute ref="xml:lang"/>
</xsd:complexType>
<xsd:element name="paragraph" type="paragraph"
substitutionGroup="struct"/>
<xsd:element name="p" type="paragraph" substitutionGroup="struct"/>
<xsd:complexType name="paragraph" mixed="true">
<xsd:choice minOccurs="0" maxOccurs="unbounded">
<xsd:group ref="allowed-within-sentence"/>
<xsd:element ref="sentence"/>
<xsd:element ref="s"/>
</xsd:choice>
<xsd:attribute ref="xml:lang"/>
</xsd:complexType>
<xsd:element name="sentence" type="sentence"
substitutionGroup="struct"/>
<xsd:element name="s" type="sentence" substitutionGroup="struct"/>
<xsd:complexType name="sentence" mixed="true">
<xsd:sequence minOccurs="0" maxOccurs="unbounded">
<xsd:group ref="allowed-within-sentence"/>
</xsd:sequence>
<xsd:attribute ref="xml:lang"/>
</xsd:complexType>
<xsd:element name="voice" type="voice" substitutionGroup="aws"/>
<xsd:complexType name="voice" mixed="true">
<xsd:choice minOccurs="0" maxOccurs="unbounded">
<xsd:group ref="allowed-within-sentence"/>
<xsd:group ref="structure"/>
</xsd:choice>
<xsd:attribute name="gender">
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="male"/>
<xsd:enumeration value="female"/>
<xsd:enumeration value="neutral"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
<xsd:attribute name="age" type="xsd:positiveInteger"/>
<xsd:attribute name="variant" type="xsd:integer"/>
<xsd:attribute name="name" type="xsd:string"/>
<xsd:attribute ref="xml:lang"/>
</xsd:complexType>
<xsd:element name="prosody" type="prosody" substitutionGroup="aws"/>
<xsd:complexType name="prosody" mixed="true">
<xsd:choice minOccurs="0" maxOccurs="unbounded">
<xsd:group ref="allowed-within-sentence"/>
<xsd:group ref="structure"/>
</xsd:choice>
<xsd:attribute name="pitch">
<xsd:simpleType>
<xsd:union memberTypes="xsd:positiveInteger
relative.change relative.change.st height.scale"/>
</xsd:simpleType>
</xsd:attribute>
<xsd:attribute name="contour" type="xsd:string"/>
<xsd:attribute name="range">
<xsd:simpleType>
<xsd:union memberTypes="number.range
relative.change relative.change.st height.scale"/>
</xsd:simpleType>
</xsd:attribute>
<xsd:attribute name="rate">
<xsd:simpleType>
<xsd:union memberTypes="xsd:positiveInteger
relative.change speed.scale"/>
</xsd:simpleType>
</xsd:attribute>
<xsd:attribute name="duration" type="duration"/>
<xsd:attribute name="volume">
<xsd:simpleType>
<xsd:union memberTypes="float.range1
relative.change volume.scale"/>
</xsd:simpleType>
</xsd:attribute>
</xsd:complexType>
<xsd:element name="audio" type="audio" substitutionGroup="aws"/>
<xsd:complexType name="audio" mixed="true">
<xsd:choice minOccurs="0" maxOccurs="unbounded">
<xsd:group ref="allowed-within-sentence"/>
<xsd:group ref="structure"/>
</xsd:choice>
<xsd:attribute name="src" type="xsd:anyURI"/>
</xsd:complexType>
<xsd:element name="emphasis" type="emphasis" substitutionGroup="aws"/>
<xsd:complexType name="emphasis" mixed="true">
<xsd:sequence minOccurs="0" maxOccurs="unbounded">
<xsd:group ref="allowed-within-sentence"/>
</xsd:sequence>
<xsd:attribute name="level" default="moderate">
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="strong"/>
<xsd:enumeration value="moderate"/>
<xsd:enumeration value="none"/>
<xsd:enumeration value="reduced"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
</xsd:complexType>
<xsd:element name="sub" type="sub" substitutionGroup="aws"/>
<xsd:complexType name="sub">
<xsd:simpleContent>
<xsd:extension base="xsd:string">
<xsd:attribute name="alias" type="xsd:string"
use="required"/>
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
<xsd:element name="say-as" type="say-as" substitutionGroup="aws"/>
<xsd:complexType name="say-as" mixed="true">
<xsd:attribute name="type" type="Say-as.datatype" use="required"/>
</xsd:complexType>
<xsd:element name="phoneme" type="phoneme" substitutionGroup="aws"/>
<xsd:complexType name="phoneme" mixed="true">
<xsd:attribute name="ph" type="xsd:string" use="required"/>
<xsd:attribute name="alphabet" type="xsd:string" default="ipa"/>
</xsd:complexType>
<xsd:element name="break" type="break" substitutionGroup="aws"/>
<xsd:complexType name="break">
<xsd:attribute name="size" default="medium">
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="large"/>
<xsd:enumeration value="medium"/>
<xsd:enumeration value="small"/>
<xsd:enumeration value="none"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
<xsd:attribute name="time" type="duration"/>
</xsd:complexType>
<xsd:element name="mark" type="mark" substitutionGroup="aws"/>
<xsd:complexType name="mark" mixed="true">
<xsd:choice minOccurs="0" maxOccurs="unbounded">
<xsd:group ref="allowed-within-sentence"/>
<xsd:group ref="structure"/>
</xsd:choice>
<xsd:attribute name="name" type="xsd:ID" use="required"/>
</xsd:complexType>
</xsd:schema>
This appendix is Normative.
SSML requires that a platform support the playing of the audio
formats specified below.
| Audio Format |
Media Type |
| Raw (headerless) 8kHz 8-bit mono mu-law [PCM] single channel.
(G.711) |
audio/basic (from http://www.ietf.org/rfc/rfc1521.txt) |
| Raw (headerless) 8kHz 8 bit mono A-law [PCM] single channel.
(G.711) |
audio/x-alaw-basic |
| WAV (RIFF header) 8kHz 8-bit mono mu-law [PCM] single
channel. |
audio/wav |
| WAV (RIFF header) 8kHz 8-bit mono A-law [PCM] single
channel. |
audio/wav |
The 'audio/basic' mime type is commonly used with the 'au'
header format as well as the headerless 8-bit 8Khz mu-law format.
If this mime type is specified for recording, the mu-law format
must be used. For playback with the 'audio/basic' mime type,
platforms must support the mu-law format and may support the 'au'
format.
This appendix is Non-Normative.
The W3C Voice Browser Working Group has applied to IETF to
register a MIME type for the Speech Synthesis Markup Language. The
current proposal is to use "application/ssml+xml".
The W3C Voice Browser Working Group has adopted the convention
of using the ".ssml" filename suffix for Speech Synthesis Markup
Language documents where "speak" is the root element.
This appendix is Non-Normative.
The following features are under consideration for versions of
the Speech Synthesis Markup Language Specification after version
1.0:
- Support for other phoneme alphabets.
- "Lowlevel" elements (fine-grained acoustic-prosodic
control)
- Intonational control elements
- "Value" element for insertion of expressions
- Support for pronunciation lexicon (when it becomes
available)
This appendix is Normative.
SSML is an application of XML 1.0 and thus supports
Unicode
which defines a standard universal character set.
Additionally, SSML provides a mechanism for precise control of
the input and output languages via the use of "xml:lang" attribute.
This facility provides:
- The ability to specify the input and output language overriding
the SSML Processor default language
- The ability to produce multi-language output
- The ability to accept input in a language which is different
from the language employed in the spoken output.