W3C REC-smil-19980615


Synchronized Multimedia Integration Language (SMIL) 1.0 Specification

W3C Recommendation 15-June-1998

This version:
http://www.w3.org/TR/1998/REC-smil-19980615
Latest SMIL 1 version:
http://www.w3.org/TR/SMIL1
Latest SMIL Recommendation:
http://www.w3.org/TR/smil
Previous version:
http://www.w3.org/TR/1998/PR-smil-19980409

Copyright © 1998 W3C (MIT, INRIA, Keio), All Rights Reserved. W3C liability, trademark, document use and software licensing rules apply. Your interactions with this site are in accordance with our public and Member privacy statements.

About this Document

This document has been prepared by the Synchronized Multimedia Working Group (WG) of the World Wide Web Consortium. The WG included the following individuals:

Acknowledgments: In addition to the working group members, the following people contributed to the SMIL effort: Bert Bos (W3C), Dan Connolly (W3C), Patrick Deunhouwer (Philips), Martin Dürst (W3C), Al  Gilman, Håkon Lie (W3C), Chris Lilley (W3C), Curtis Reynolds (RealNetworks), Michael Riesman, Curtis Reynolds (RealNetworks), Henning Schulzrinne (Columbia University) and Koga Youichirou (W3C).

Editor: Philipp Hoschka, W3C (hoschka@w3.org)

Abstract

This document specifies version 1 of the Synchronized Multimedia Integration Language (SMIL 1.0, pronounced "smile"). SMIL allows integrating a set of independent multimedia objects into a synchronized multimedia presentation. Using SMIL, an author can

  1. describe the temporal behavior of the presentation
  2. describe the layout of the presentation on a screen
  3. associate hyperlinks with media objects

This specification is structured as follows: Section 1 presents the specification approach. Section 2 defines the "smil" element. Section 3 defines the elements  that can be contained in the head part of a SMIL document. Section 4 defines the elements that can be contained in the body part of a SMIL document. In particular, this Section defines the time model used in SMIL. Section 5 describes the SMIL DTD.

Status of this Document

This document was edited in place on 15 sept 2015, to fix a broken link in the above "latest version".

This document has been reviewed by W3C Members and other interested parties and has been endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited as a normative reference from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.

Comments on this Recommendation may be sent to the public mailing list www-smil@w3.org.

Available languages

The English version of this specification is the only normative version. However, for translations in other languages see http://www.w3.org/AudioVideo/SMIL/translations.

Errata

The list of known errors in this specification is available at http://www.w3.org/AudioVideo/SMIL/errata.

Table of Contents

1 Specification Approach

SMIL documents are XML 1.0 documents [XML10]. The reader is expected to be familiar with the concepts and terms defined in XML 1.0.

This specification does not rely on particular features defined in URLs that cannot potentially be expressed using URNs. Therefore, the more generic term URI [URI] is used throughout the specification.

The syntax of SMIL documents is defined by the DTD in Section 5.2. The syntax of an attribute value that cannot be defined using the DTD notation is defined together with the first element using an attribute that can contain the attribute value. The syntax of such attribute values is defined using the Extended Backus-Naur Form (EBNF) defined in the XML 1.0 specification.

An element definition is structured as follows: First, all attributes of the element are defined in alphabetical order. An attribute is defined in the following way: If the attribute is used by an element for the first time in the specification, the semantics of the attribute are defined. If the attribute has already been used by another element, the specification refers to the definition of the attribute in the first element that used it. The definition of element attributes is followed by the definition of any attribute values whose syntax cannot be defined using the DTD notation.  The final section in an element definition specifies the element content.

2 The smil Element

Element Attributes

The "smil" element can have the following attribute:

id
This attribute uniquely identifies an element within a document. Its value is an XML identifier.

Element Content

The "smil" element can contain the following children:

body
Defined in Section 4.1
head
Defined in Section 3.1

3 The Document Head

3.1 The head Element

The "head" element contains information that is not related to the temporal behavior of the presentation.

Element Attributes

The "head" element can have the following attribute:

id
Defined in Section 2

Element Content

The "head" element can contain the following children:

layout
Defined in Section 3.2
meta
Defined in Section 3.4
switch
Defined in Section 4.3

The "head" element may contain any number of "meta" elements and either a "layout" element or a "switch" element.

3.2 The layout Element

The "layout" element determines how the elements in the document's body are positioned on an abstract rendering surface (either visual or acoustic).

If a document contains no layout element, the positioning of the body elements is implementation-dependent.

A SMIL document can contain multiple alternative layouts by enclosing several layout elements within a "switch" element (defined in Section 4.3). This can be used for example to describe the document's layout using different layout languages.

The following example shows how CSS2 can be used as alternative to the SMIL basic layout language (defined in Section 3.3):

<smil>
  <head>
    <switch>
     <layout type="text/css">
        [region="r"] { top: 20px; left: 20px }
     </layout>
     <layout>
       <region id="r" top="20" left="20" />
     </layout>
   </switch>
   </head>
   <body>
     <seq>
       <img region="r" src="http://www.w3.org/test" dur="10s" />
     </seq>
   </body>
</smil>

(note that in this example, both layout alternatives result in the same layout)

Element Attributes

id
Defined in Section 2
type
This attribute specifies which layout language is used in the layout element. If the player does not understand this language, it must skip all content up until the next "</layout>" tag. The default value of the type attribute is "text/smil-basic-layout".

Element Content

If the type attribute of the layout element has the value "text/smil-basic-layout", it can contain the following elements:

region
Defined in Section 3.3.1
root-layout
Defined in Section 3.3.2

If the type attribute of the "layout" element has another value, the element contains character data.

3.3 SMIL Basic Layout Language

This section defines a basic layout language for SMIL. SMIL basic layout is consistent with the visual rendering model defined in CSS2, it reuses the formatting properties defined by the CSS2 specification, and newly introduces the "fit" attribute [CSS2]. The reader is expected to be familiar with the concepts and terms defined in CSS2.

SMIL basic layout only controls the layout of media object elements (defined in Section 4.2.3). It is illegal to use SMIL basic layout for other SMIL elements.

The type identifier for SMIL basic layout is "text/smil-basic-layout".

Fixed Property Values

The following stylesheet defines the values of the CSS2 properties "display" and "position" that are valid in SMIL basic layout. These property values are fixed:

a           {display:block}
anchor      {display:block}
animation   {display: block;
             position: absolute}
body        {display: block}
head        {display: none}
img         {display: block;
             position: absolute}
layout      {display: none}  
meta        {display: none}
par         {display: block}
region      {display: none}
ref	    {display: block;
             position: absolute}
root-layout {display: none}
seq         {display: block}
smil        {display: block}
switch      {display:block}
text        {display: block;
             position: absolute}
textstream  {display: block;
             position: absolute}
video       {display: block;
             position: absolute}

Note that as a result of these definitions, all absolutely positioned elements (animation, img, ref, text, textstream and video) are contained within a single containing block defined by the content content edge of the root element (smil).

Default Values

SMIL basic layout defines default values for all layout-related attributes. These are consistent with the initial values of the corresponding properties in CSS2.

If the author wants to select the default layout values for all media object elements in a document, the document must contain an empty layout element of type "text/smil-basic-layout" such as:

<layout type="text/smil-basic-layout"></layout>

3.3.1 The region Element

The region element controls the position, size and scaling of media object elements.

In the following example fragment, the position of a text element is set to a 5 pixel distance from the top border of the rendering window:

<smil>
  <head>
    <layout>
      <region id="a" top="5" />
    </layout>
  </head>
  <body>
    <text region="a" src="text.html" dur="10s" />
  </body>
</smil>

Element  Attributes

The "region" element can have the following attributes:

background-color
The use and definition of this attribute are identical to the "background-color" property in the CSS2 specification, except that SMIL basic layout does not require support for "system colors".
If the background-color attribute is absent, the background is transparent.
fit
This attribute specifies the behavior if the intrinsic height and width of a visual media object differ from the values specified by the height and width attributes in the "region" element. This attribute does not have a 1-1 mapping onto a CSS2 property, but can be simulated in CSS2.
This attribute can have the following values:
fill
Scale the object's height and width independently so that the content just touches all edges of the box.
hidden
  • If the intrinsic height (width) of the media object element is smaller than the height (width) defined in the "region" element, render the object starting from the top (left) edge and fill up the remaining height (width) with the background color.
  • If the intrinsic height (width) of the media object element is greater than the height (width) defined in the "region" element, render the object starting from the top (left) edge until the height (width) defined in the "region" element is reached, and clip the parts of the object below (right of) the height (width).
meet
Scale the visual media object while preserving its aspect ratio until its height or width is equal to the value specified by the height or width attributes, while none of the content is clipped. The object's left top corner is positioned at the top-left coordinates of the box, and empty space at the left or bottom is filled up with the background color.
scroll
A scrolling mechanism should be invoked when the element's rendered contents exceed its bounds.
slice
Scale the visual media object while preserving its aspect ratio so that its height or width are equal to the value specified by the height and width attributes while some of the content may get clipped. Depending on the exact situation, either a horizontal or a vertical slice of the visual media object is displayed. Overflow width is clipped from the right of the media object. Overflow height is clipped from the bottom of the media object.

The default value of "fill" is "hidden".

height
The use and definition of this attribute are identical to the "height" property in the CSS2 specification. Attribute values can be "percentage" values, and a variation of the "length" values defined in CSS2. For "length" values, SMIL basic layout only supports pixel units as defined in CSS2. It allows to leave out the "px" unit qualifier in pixel values (the "px" qualifier is required in CSS2).
id
Defined in Section 2
A region element is applied to a positionable element by setting the region attribute of the positionable element to the id value of the region.
The "id" attribute is required for "region" elements.
left
The use and definition of this attribute are identical to the "left" property in the CSS2 specification. Attribute values have the same restrictions as the attribute values of the "height" attribute.
The default value is zero.
skip-content
This attribute is introduced for future extensibility of SMIL (see Appendix). It is interpreted in the following two cases:

If the value of the "skip-content" attribute is "true", and one of the cases above apply, the content of the element is ignored. If the value is "false", the content of the element is processed.
The default value for  "skip-content" is "true".

title
This attribute offers advisory information about the element for which it is set. Values of the title attribute may be rendered by user agents in a variety of ways. For instance, visual browsers frequently display the title as a "tool tip" (a short message that appears when the pointing device pauses over an object).
It  is strongly recommended that all "region" elements have a "title" attribute with a meaningful description. Authoring tools should ensure that no element can be introduced into a SMIL document without this attribute.
top
The use and definition of this attribute are identical to the "top" property in the CSS2 specification. Attribute values have the same restrictions as the attribute values of the "height" attribute.
The default value is zero.
width
The use and definition of this attribute are identical to the "width" property in the CSS2 specification. Attribute values have the same restrictions as the attribute values of the "height" attribute.
z-index
The use and definition of this attribute are identical to the "z-index" property in the CSS2 specification, with the following exception:

Element Content

"region" is an empty element.

3.3.2 The root-layout element

The "root-layout" element determines the value of the layout properties of the root element, which in turn determines the size of the viewport, e.g. the window in which the SMIL presentation is rendered.

If a document contains more than one "root-layout" element, this is an error, and the document should not be displayed.

Element Attributes

The "root-layout" element can have the following attributes:

background-color
Defined in Section 3.3.1
height
Defined in Section 3.3.1
Sets the height of the root element. Only length values are allowed.
id
Defined in Section 2
skip-content
Defined in Section 3.3.1
title
Defined in Section 3.3.1
width
Defined in Section 3.3.1
Sets the width of the root element. Only length values are allowed.

Element Content

"root-layout" is an empty element.

3.4 The meta Element

The "meta" element can be used to define properties of a document (e.g., author, expiration date, a list of key words, etc.) and assign values to those properties. Each "meta" element specifies a single property/value pair.

Element Attributes

The "meta" element can have the following attributes:

content
This attribute specifies the value of the property defined in the meta element.
The "content" attribute is required for "meta" elements.
id
Defined in Section 2
name
This attribute identifies the property defined in the meta element.
The "name" attribute is required for "meta" elements.
skip-content
Defined in Section 3.3.1

The list of properties is open-ended. This specification defines the following properties:

base
The value of this property determines the base URI for all relative URIs used in the document.
pics-label or PICS-Label
The value of this property specifies a valid rating label for the document as defined by PICS [PICS].
title
The value of this property contains the title of the presentation.

Element Content

"meta" is an empty element.

4 The Document Body

4.1 The body Element

The "body" element contains information that is related to the temporal and linking behavior of the document. It implicitly defines a "seq" element (defined in Section 4.2.2, see Section 4.2.4 for a definition of the temporal semantics of the "body" element).

Element Attributes

The "body" element can have the following attribute:

id
Defined in Section 2

Element Content

The "body" element can contain the following children:

a
Defined in Section 4.5.1
animation
Defined in Section 4.2.3
audio
Defined in Section 4.2.3
img
Defined in Section 4.2.3
par
Defined in Section 4.2.1
ref
Defined in Section 4.2.3
seq
Defined in Section 4.2.2
switch
Defined in Section 4.3
text
Defined in Section 4.2.3
textstream
Defined in Section 4.2.3
video
Defined in Section 4.2.3

4.2 Synchronization Elements

4.2.1 The par Element

The children of a par element can overlap in time. The textual order of appearance of children in a par has no significance for the timing of their presentation.

Element Attributes

The "par" element can have the following attributes:

abstract
A brief description of the content contained in the element.
author
The name of the author of the content contained in the element.
begin
This attribute specifies the time for the explicit begin of an element. See Section 4.2.4 for a definition of its semantics.
The attribute can contain the following two types of values:
delay-value
A delay value is a clock-value measuring presentation time. Presentation time advances at the speed of the presentation. It behaves like the timecode shown on a counter of a tape-deck. It can be stopped, decreased or increased either by user actions, or by the player itself.
The semantics of a delay value depend on the element's first ancestor that is a synchronization element (i.e. ancestors that are "a" or "switch" elements are ignored):
  • If this ancestor is a "par" element, the value defines a delay from the effective begin of that element (see Figure 4.1).
  • If this ancestor is a "seq" element (defined in Section 4.2.2), the value defines a delay from the effective end of the first lexical predecessor that is a synchronization element (see Figure 4.2).
event-value
The element begins when a certain event occurs (see Figure 4.3). Its value is an element-event (see Definition below).
The element generating the event must be "in scope". The set of "in scope" elements S is determined as follows:
  1. Take all children from the element's first ancestor that is a synchronization element and add them to S.
  2. Remove all "a" and "switch" elements from S. Add the children of all "a" elements to S, unless they are "switch" elements.

The resulting set S is the set of "in scope" elements.


<par>
  <audio id="a" begin="6s" src="audio" />
</par>

delay in 'par' element D


Figure 4.1: Using a delay value within a "par" element
<seq>
  <audio src="audio1" />
  <audio begin="5s" src="audio2" />
</seq>

delay in 'seq' element D


Figure 4.2: Using a delay value within a "seq" element
<par>
  <audio id="a" begin="6s" ... />
  <img  begin="id(a)(4s)" ... />
</par>

element with event value D


Figure 4.3: Synchronization attribute with element event value
copyright
The copyright notice of the content contained in the element.
dur
This attribute specifies the explicit duration of an element. See Section 4.2.4 for a definition of its semantics. The attribute value can be a clock value, or the string "indefinite".
end
This attribute specifies the explicit end of an element. See Section 4.2.4 for a definition of its semantics. The attribute can contain the same types of attribute values as the "begin" attribute.
endsync
For a definition of the semantics of this attribute, see Section 4.2.4. The attribute can have the following values:

The default value of "endsync" is "last".

id
Defined in Section 2
region
This attribute specifies an abstract rendering surface (either visual or acoustic) defined within the layout section of the document. Its value must be an XML identifier. If no rendering surface with this id is defined in the layout section, the values of the formatting properties of this element are determined by the default layout.
The "region" attribute on "par" elements cannot be used by the basic layout language for SMIL defined in this specification. It is added for completeness, since it may be required by other layout languages.
repeat
For a definition of the semantics of this attribute, see Section 4.2.4. The attribute value can be an integer, or the string "indefinite". The default value is 1.
system-bitrate
Defined in Section 4.4
system-captions
Defined in Section 4.4
system-language
Defined in Section 4.4
system-overdub-or-caption
Defined in Section 4.4
system-required
Defined in Section 4.4
system-screen-size
Defined in Section 4.4
system-screen-depth
Defined in Section 4.4
title
Defined in Section 3.3.1
It  is strongly recommended that all "par" elements have a "title" attribute with a meaningful description. Authoring tools should ensure that no element can be introduced into a SMIL document without this attribute.

Note on Synchronization between Children

The accuracy of synchronization between the children in a parallel group is implementation-dependent. Take the example of synchronization in case of playback delays, i.e. the behavior when the "par" element contains two or more continuous media types such as audio or video, and one of them experiences a delay.
A player can show the following synchronization behaviors:

hard synchronization
The player synchronizes the children in the "par" element to a common clock (see Figure 4.4 a)).
soft synchronization
Each child of the "par" element has its own clock, which runs independently of the clocks of other children in the "par" element (see Figure 4.4 b)).


hard synchronization D

a) hard synchronization: Delay in video: Either the audio is stopped, or some video frames are dropped. The exact behavior is implementation-dependent

soft synchronization D

b) soft synchronization


Figure 4.4: Effect of a delay on playout schedule for players using different synchronization policies

Attribute Values

clock value
Clock values have the following syntax:
Clock-val             ::= Full-clock-val | Partial-clock-val | Timecount-val
Full-clock-val        ::= Hours ":" Minutes ":" Seconds ("." Fraction)?
Partial-clock-val     ::= Minutes ":" Seconds ("." Fraction)?
Timecount-val         ::= Timecount ("." Fraction)?
                          ("h" | "min" | "s" | "ms")? ; default is "s"
Hours                 ::= 2DIGIT; any positive number
Minutes               ::= 2DIGIT; range from 00 to 59
Seconds               ::= 2DIGIT; range from 00 to 59
Fraction	      ::= DIGIT+
Timecount             ::= DIGIT+
2DIGIT		      ::= DIGIT DIGIT
DIGIT		      ::= [0-9]

The following are examples of legal clock values:


A fraction x with n digits represents the following value:

x * 1/10**n

Examples:

00.5s = 5 * 1/10 seconds = 500 milliseconds
00:00.005 = 5 * 1/1000 seconds = 5 milliseconds

element-event value
An element event value specifies a particular event in a synchronization element.
An element event has the following syntax:
Element-event     ::= "id(" Event-source ")(" Event ")"
Event-source      ::= Id-value
Event             ::= "begin" | Clock-val | "end"
The following events are defined:
begin
This event is generated at an element's effective begin.
Example use: begin="id(x)(begin)"
clock-val
This event is generated when a clock associated with an element reaches a particular value. This clock starts at 0 at the element's effective begin. For "par" and "seq" elements, the clock gives the presentation time elapsed since the effective begin of the element. For media object elements, the semantics are implementation-dependent. The clock may either give presentation time elapsed since the effective begin, or it may give the media time of the object. The latter may differ from the presentation time that elapsed since the object's display was started e.g. due to rendering or network delays, and is the recommended approach.
It is an error to use a clock value that exceeds the value of the effective duration of the element generating the event.

Example use: begin="id(x)(45s)"

end
This event is generated at the element's effective end.
Example use: begin="id(x)(end)"

Element Content

The par element can contain the following children:

a
Defined in Section 4.5.1
animation
Defined in Section 4.2.3
audio
Defined in Section 4.2.3
img
Defined in Section 4.2.3
par
Defined in Section 4.2.1
ref
Defined in Section 4.2.3
seq
Defined in Section 4.2.2
switch
Defined in Section 4.3
text
Defined in Section 4.2.3
textstream
Defined in Section 4.2.3
video
Defined in Section 4.2.3

All of these elements may appear multiple times as direct children of a par element.

4.2.2 The seq Element

The children of a "seq" element form a temporal sequence.

Attributes

The seq element can have the following attributes:

abstract
Defined in Section 4.2.1
author
Defined in Section 4.2.1
begin
Defined in Section 4.2.1
copyright
Defined in Section 4.2.1
dur
Defined in Section 4.2.1
end
Defined in Section 4.2.1
id
Defined in Section 2
region
Defined in Section 4.2.1
The region attribute on "seq" elements cannot be used by the basic layout language for SMIL defined in this specification. It is added for completeness, since it may be required by other layout languages.
repeat
Defined in Section 4.2.1
system-bitrate
Defined in Section 4.4
system-captions
Defined in Section 4.4
system-language
Defined in Section 4.4
system-overdub-or-caption
Defined in Section 4.4
system-required
Defined in Section 4.4
system-screen-size
Defined in Section 4.4
system-screen-depth
Defined in Section 4.4
title
Defined in Section 3.3.1
It  is strongly recommended that all "seq" elements have a "title" attribute with a meaningful description. Authoring tools should ensure that no element can be introduced into a SMIL document without this attribute.

Element Content

The seq element can contain the following children:

a
Defined in Section 4.5.1
animation
Defined in Section 4.2.3
audio
Defined in Section 4.2.3
img
Defined in Section 4.2.3
par
Defined in Section 4.2.1
ref
Defined in Section 4.2.3
seq
Defined in Section 4.2.2
switch
Defined in Section 4.3
text
Defined in Section 4.2.3
textstream
Defined in Section 4.2.3
video
Defined in Section 4.2.3

4.2.3 Media Object Elements: The ref, animation, audio,img, video,text and textstream elements

The media object elements allow the inclusion of media objects into a SMIL presentation. Media objects are included by reference (using a URI).

There are two types of media objects: media objects with an intrinsic duration (e.g. video, audio) (also called "continuous media"), and media objects without intrinsic duration (e.g. text, image) (also called "discrete media").

Anchors and links can be attached to visual media objects, i.e. media objects rendered on a visual abstract rendering surface.

When playing back a media object, the player must not derive the exact type of the media object from the name of the media object element. Instead, it must rely solely on other sources about the type, such as type information contained in the "type" attribute, or the type information communicated by a server or the operating system.

Authors, however, should make sure that the group into which of the media object falls (animation, audio, img, video, text or textstream) is reflected in the element name. This is in order to increase the readability of the SMIL document. When in doubt about the group of a media object, authors should use the generic "ref" element.

Element Attributes

Media object elements can have the following attributes:

abstract
Defined in Section 4.2.1
alt
For user agents that cannot display a particular media-object, this attribute specifies alternate text. It  is strongly recommended that all media object elements have an "alt" attribute with a meaningful description. Authoring tools should ensure that no element can be introduced into a SMIL document without this attribute.
author
Defined in Section 4.2.1
begin
Defined in Section 4.2.1
clip-begin
The clip-begin attribute specifies the beginning of a sub-clip of a continuous media object as offset from the start of the media object.
Values in the clip-begin attribute have the following syntax:
Clip-time-value   ::= Metric "=" ( Clock-val | Smpte-val )
Metric            ::= Smpte-type | "npt"
Smpte-type        ::= "smpte" | "smpte-30-drop" | "smpte-25"
Smpte-val         ::= Hours ":" Minutes ":" Seconds 
                      [ ":" Frames [ "." Subframes ]]
Hours             ::= 2DIGIT
Minutes           ::= 2DIGIT
Seconds           ::= 2DIGIT
Frames            ::= 2DIGIT
Subframes         ::= 2DIGIT

The value of this attribute consists of a metric specifier, followed by a time value whose syntax and semantics depend on the metric specifier. The following formats are allowed:

SMPTE Timestamp
SMPTE time codes [SMPTE] can be used for frame-level access accuracy. The metric specifier can have the following values:
smpte
smpte-30-drop
These values indicate the use of the "SMPTE 30 drop" format with 29.97 frames per second. The "frames" field in the time value can assume the values 0 through 29. The difference between 30 and 29.97 frames per second is handled by dropping the first two frame indices (values 00 and 01) of every minute, except every tenth minute.
smpte-25
The "frames" field in the time specification can assume the values 0 through 24.

The time value has the format hours:minutes:seconds:frames.subframes. If the frame value is zero, it may be omitted. Subframes are measured in one-hundredth of a frame.
Examples:
clip-begin="smpte=10:12:33:20"

Normal Play Time
Normal Play Time expresses time in terms of SMIL clock values. The metric specifier is "npt", and the syntax of the time value is identical to the syntax of SMIL clock values.
Examples:
clip-begin="npt=123.45s"
clip-begin="npt=12:05:35.3
"
clip-end
The clip-end attribute specifies the end of a sub-clip of a continuous media object (such as audio, video or another presentation) that should be played. It uses the same attribute value syntax as the clip-begin attribute.
If the value of the "clip-end" attribute exceeds the duration of the media object, the value is ignored, and the clip end is set equal to the effective end of the media object.
copyright
Defined in Section 4.2.1
dur
Defined in Section 4.2.1
end
Defined in Section 4.2.1
fill
For a definition of the semantics of this attribute, see Section 4.2.4. The attribute can have the values "remove" and "freeze".
id
Defined in Section 2
longdesc
This attribute specifies a link (URI) to a long description of a media object. This description should supplement the short description provided using the alt attribute. When the media-object has associated anchors, this attribute should provide information about the anchor's contents.
region
Defined in Section 4.2.1
src
The value of the src attribute is the URI of the media object.
system-bitrate
Defined in Section 4.4
system-captions
Defined in Section 4.4
system-language
Defined in Section 4.4
system-overdub-or-caption
Defined in Section 4.4
system-required
Defined in Section 4.4
system-screen-size
Defined in Section 4.4
system-screen-depth
Defined in Section 4.4
title
Defined in Section 3.3.1
It is strongly recommended that all media object elements have a "title" attribute with a meaningful description. Authoring tools should ensure that no element can be introduced into a SMIL document without this attribute.
type
MIME type of the media object referenced by the "src" attribute.

Element Content

Media Object Elements can contain the following element:

anchor
Defined in Section 4.5.2

4.2.4 SMIL Time Model

4.2.4.1 Time Model Values

In the following discussion, the term "element" refers to synchronization elements only.

For each element we define the implicit, explicit, desired, and effective begin, duration, and end.

The effective begin/duration/end specify what the reader of the document will perceive.

The implicit, explicit, and desired values are auxiliary values used to define the effective values.

The rules for calculating each of these values for the elements defined in SMIL 1.0 are described in the next section.

  1. Each element in SMIL has an implicit begin.
  2. Each element can be assigned an explicit begin by adding a "begin" attribute to the element:
    begin = "value of explicit-begin"

    It is an error if the explicit begin is earlier than the implicit begin of the element.

  3. Each element in SMIL has an implicit end.
  4. Each element can be assigned an explicit end by adding an "end" attribute to the element:
    end = "value of explicit-end"
  5. The implicit duration of an element is the difference between the implicit end and the implicit begin.
  6. Each element in SMIL can be assigned an explicit duration by adding a "dur" attribute to the element:
    dur = "value of explicit-duration"
  7. The desired begin of an element is equal to the explicit begin if one is given, otherwise the desired begin is equal to the implicit begin.
  8. Each element has a desired end.
  9. The desired duration of an element is the difference between the desired end and the desired begin.
  10. Each element has an effective begin.
  11. Each element has an effective end. (Note: the effective end of a child element can never be later than the effective end of its parent.)
  12. The effective duration of an element is the difference between the effective end and the effective begin.
4.2.4.2 Determining Time Model Values for SMIL 1.0 Elements

This section defines how time model values are calculated for the synchronization elements of SMIL 1.0 in cases that are not covered by the rules in Section 4.2.4.1.

Determining the implicit begin of an element

Determining the implicit end of an element

The first description that matches the element is the one that is to be used:

Determining the desired end of an element

Determining the desired begin of an element

The desired begin of an element is determined by using rule 7 in Section 4.2.4.1.

Determining the effective begin of an element

The effective begin of an element is equal to the desired begin of the element, unless the effective end of the parent element is earlier than this time, in which case the element is not shown at all.

Determining the effective end of an element

4.3 The switch Element

The switch element allows an author to specify a set of alternative elements from which only one acceptable element should be chosen. An element is acceptable if the element is a SMIL 1.0 element, the media-type can be decoded, and all of the test-attributes (see Section 4.4) of the element evaluate to "true".

An element is selected as follows: the player evaluates the elements in the order in which they occur in the switch element. The first acceptable element is selected at the exclusion of all other elements within the switch.

Thus, authors should order the alternatives from the most desirable to the least desirable. Furthermore, authors should place a relatively fail-safe alternative as the last item in the <switch> so that at least one item within the switch is chosen (unless this is explicitly not desired). Implementations should NOT arbitrarily pick an object within a <switch> when test-attributes for all fail.

Note that http URIs provide for content-negotiation, which may be an alternative to using the "switch" element in some cases.

Attributes

The switch element can have the following attributes:

id
Defined in Section 2
title
Defined in Section 3.3.1
It  is strongly recommended that all switch elements have a "title" attribute with a meaningful description Authoring tools should ensure that no element can be introduced into a SMIL document without this attribute.

Element Content

If the "switch" element is used as a direct or indirect child of a "body" element, it can contain the following children:

a
Defined in Section 4.5.1
animation
Defined in Section 4.2.3
audio
Defined in Section 4.2.3
img
Defined in Section 4.2.3
par
Defined in Section 4.2.1
ref
Defined in Section 4.2.3
seq
Defined in Section 4.2.2
switch
Defined in Section 4.3
text
Defined in Section 4.2.3
textstream
Defined in Section 4.2.3
video
Defined in Section 4.2.3

All of these elements may appear multiple times as children of a "switch" element.

If the "switch" element is used within a "head" element, it can contain the following child:

layout
Defined in Section 3.2
Multiple layout elements may occur within the switch element.

4.4 Test Attributes

This specification defines a list of test attributes that can be added to any synchronization element, and that test system capabilities and settings. Conceptually, these attributes represent boolean tests. When one of the test attributes specified for an element evaluates to "false", the element carrying this attribute is ignored.

Within the list below, the concept of "user preference" may show up. User preferences are usually set by the playback engine using a preferences dialog box, but this specification does not place any restrictions on how such preferences are communicated from the user to the SMIL player.

The following test attributes are defined in SMIL 1.0:

system-bitrate
This attribute specifies the approximate bandwidth, in bits per second available to the system. The measurement of bandwidth is application specific, meaning that applications may use sophisticated measurement of end-to-end connectivity, or a simple static setting controlled by the user. In the latter case, this could for instance be used to make a choice based on the users connection to the network. Typical values for modem users would be 14400, 28800, 56000 bit/s etc. Evaluates to "true" if the available system bitrate is equal to or greater than the given value. Evaluates to "false" if the available system bitrate is less than the given value.
The attribute can assume any integer value greater than 0. If the value exceeds an implementation-defined maximum bandwidth value, the attribute always evaluates to "false".
system-captions
This attribute allows authors to distinguish between a redundant text equivalent of the audio portion of the presentation (intended for a audiences such as those with hearing disabilities or those learning to read who want or need this information) and text intended for a wide audience. The attribute can has the value "on" if the user has indicated a desire to see closed-captioning information, and it has the value "off" if the user has indicated that they don't wish to see such information. Evaluates to "true" if the value is "on", and evaluates to "false" if the value is "off".
system-language
The attribute value is a comma-separated list of language names as defined in [RFC1766].

Evaluates to "true" if one of the languages indicated by user preferences exactly equals one of the languages given in the value of this parameter, or if one of the languages indicated by

user preferences exactly equals a prefix of one of the languages given in the value of this parameter such that the first tag character following the prefix is "-".

Evaluates to "false" otherwise.

Note: This use of a prefix matching rule does not imply that language tags are assigned to languages in such a way that it is always true that if a user understands a language with a certain tag, then this user will also understand all languages with tags for which this tag is a prefix.

The prefix rule simply allows the use of prefix tags if this is the case.

Implementation note: When making the choice of linguistic preference available to the user, implementors should take into account the fact that users are not familiar with the details of language matching as described above, and should provide appropriate guidance. As an example, users may assume that on selecting "en-gb", they will be served any kind of English document if British English is not available. The user interface for setting user preferences should guide the user to add "en" to get the best matching behavior.

Multiple languages MAY be listed for content that is intended for multiple audiences. For example, a rendition of the "Treaty of Waitangi", presented simultaneously in the original Maori and English versions, would call for:

            <audio src="foo.rm" system-language="mi, en"/>

However, just because multiple languages are present within the object on which the system-language test attribute is placed, this does not mean that it is intended for multiple linguistic audiences. An example would be a beginner's language primer, such as "A First Lesson in Latin," which is clearly intended to be used by an English-literate audience. In this case, the system-language test attribute should only include "en".

Authoring note: Authors should realize that if several alternative language objects are enclosed in a "switch", and none of them matches, this may lead to situations such as a video being shown without any audio track. It is thus recommended to include a "catch-all" choice at the end of such a switch which is acceptable in all cases.

system-overdub-or-caption
This attribute is a setting which determines if users prefer overdubbing or captioning when the option is available. The attribute can have the values "caption" and "overdub". Evaluates to "true" if the user preference matches this attribute value. Evaluates to "false" if they do not match.
system-required
This attribute specifies the name of an extension. Evaluates to "true" if the extension is supported by the implementation, otherwise, this evaluates to "false". In a future version of SMIL, this attribute value will be an XML namespace [NAMESPACES].
system-screen-size
Attribute values have the following syntax:
screen-size-val ::= screen-height"X"screen-width
Each of these is a pixel value, and must be an integer value greater than 0.  Evaluates to "true" if the SMIL playback engine is capable of displaying a presentation of the given size. Evaluates to "false" if the SMIL playback engine is only capable of displaying a smaller presentation.
system-screen-depth
This attribute specifies the depth of the screen color palette in bits required for displaying the element. The value must be greater than 0. Typical values are 1, 8, 24 .... Evaluates to "true" if the SMIL playback engine is capable of displaying images or video with the given color depth. Evaluates to "false" if the SMIL playback engine is only capable of displaying images or video with a smaller color depth.

Examples

1) Choosing between content with different bitrate

In a common scenario, implementations may wish to allow for selection via a "system-bitrate" parameter on elements. The media player evaluates each of the "choices" (elements within the switch) one at a time, looking for an acceptable bitrate given the known characteristics of the link between the media player and media server.

...
<par>
  <text .../>
  <switch>
    <par system-bitrate="40000">
    ...
    </par>
    <par system-bitrate="24000">
    ...
    </par>
    <par system-bitrate="10000">
    ........
    </par>
  </switch>
</par>
...

2) Choosing between audio resources with different bitrate

The elements within the switch may be any combination of elements. For instance, one could merely be specifying an alternate audio track:

...
<switch>
   <audio src="joe-audio-better-quality" system-bitrate="16000" />
   <audio src="joe-audio" system-bitrate="8000" />
</switch>
...

3) Choosing between audio resources in different languages

In the following example, an audio resource is available both in French and in English. Based on the user's preferred language, the player can choose one of these audio resources.

...
<switch>
   <audio src="joe-audio-french" system-language="fr"/>
   <audio src="joe-audio-english" system-language="en"/>
</switch>
...

4) Choosing between content written for different screens

In the following example, the presentation contains alternative parts designed for screens with different resolutions and bit-depths. Depending on the particular characteristics of the screen, the player can choose one of the alternatives.

...
<par>
  <text .../>
  <switch>
    <par system-screen-size="1280X1024" system-screen-depth="16">
    ........
    </par>
    <par system-screen-size="640X480" system-screen-depth="32">
    ...
    </par>
    <par system-screen-size="640X480" system-screen-depth="16">
    ...
    </par>
  </switch>
</par>
...

5) Distinguishing caption tracks from stock tickers

In the following example, captions are shown only if the user wants captions on.

...
<seq>
  <par>
    <audio      src="audio.rm"/>
    <video      src="video.rm"/>
    <textstream src="stockticker.rtx"/>
    <textstream src="closed-caps.rtx" system-captions="on"/>
  </par>
</seq>
...

6) Choosing the language of overdub and caption tracks

In the following example, a French-language movie is available with English, German, and Dutch overdub and caption tracks. The following SMIL segment expresses this, and switches on the alternatives that the user prefers.

...
<par>
  <switch>
    <audio src="movie-aud-en.rm" system-language="en"
                system-overdub-or-caption="overdub"/>
    <audio src="movie-aud-de.rm" system-language="de"
                system-overdub-or-caption="overdub"/>
    <audio src="movie-aud-nl.rm" system-language="nl"
                system-overdub-or-caption="overdub"/>
     <!-- French for everyone else -->
     <audio src="movie-aud-fr.rm"/>
   </switch>
   <video src="movie-vid.rm"/>
   <switch>
     <textstream src="movie-caps-en.rtx" system-language="en"
                 system-overdub-or-caption="caption"/>
     <textstream src="movie-caps-de.rtx" system-language="de"
                system-overdub-or-caption="caption"/>
     <textstream src="movie-caps-nl.rtx" system-language="nl"
                 system-overdub-or-caption="caption"/>
     <!-- French captions for those that really want them -->
     <textstream src="movie-caps-fr.rtx" system-captions="on"/>
   </switch>
</par>
...

4.5 Hyperlinking Elements

The link elements allows the description of navigational links between objects.

SMIL provides only for in-line link elements. Links are limited to uni-directional single-headed links (i.e. all links have exactly one source and one destination resource). All links in SMIL are actuated by the user.

Handling of Links in Embedded Documents

Due to its integrating nature, the presentation of a SMIL document may involve other (non-SMIL) applications or plug-ins. For example, a SMIL browser may use an HTML plug-in to display an embedded HTML page. Vice versa, an HTML browser may use a SMIL plug-in to display a SMIL document embedded in an HTML page.

In such presentations, links may be defined by documents at different levels and conflicts may arise. In this case, the link defined by the containing document should take precedence over the link defined by the embedded object. Note that since this might require communication between the browser and the plug-in, SMIL implementations may choose not to comply with this recommendation.

If a link is defined in an embedded SMIL document, traversal of the link affects only the embedded SMIL document.

If a link is defined in a non-SMIL document which is embedded in a SMIL document, link traversal can only affect the presentation of the embedded document and not the presentation of the containing SMIL document. This restriction may be released in future versions of SMIL.

Addressing

SMIL supports name fragment identifiers and the '#' connector. This means that SMIL supports locators as currently used in HTML (e.g. it uses locators of the form "http://foo.com/some/path#anchor1").

Linking to SMIL Fragments

A locator that points to a SMIL document may contain a fragment part (e.g. http://www.w3.org/test.smi#par1). The fragment part is an id value that identifies one of the elements within the referenced SMIL document. If a link containing a fragment part is followed, the presentation should start as if the user had fast-forwarded the presentation represented by the destination document to the effective begin of the element designated by the fragment.

The following special cases can occur:

  1. The element addressed by the link has a "repeat" attribute.
    1. If the value of the "repeat" attribute is N, all N repetitions of the element are played.
    2. If the value of the "repeat" attribute is "indefinite", playback ends according to the rules defined for repeat value "indefinite".
  2. The element addressed by the link is contained within another element that contains a "repeat" attribute.
    1. If the value of the "repeat" attribute is N, playback starts at the beginning of the element addressed by the link, followed by N-1 repetitions of the element containing the "repeat" attribute.
    2. If the value of the "repeat" attribute is "indefinite", playback starts at the beginning of the element addressed by the link. Playback ends according to the rules defined for repeat value "indefinite".
  3. The element addressed by the link is content of a "switch" element: It is forbidden to link to elements that are the content of "switch" elements.

4.5.1 The a Element

The functionality of the "a" element is very similar to the functionality of the "a" element in HTML 4.0 [HTML40] . SMIL adds an attribute "show" that controls the temporal behavior of the source when the link is followed. For synchronization purposes, the "a" element is transparent, i.e. it does not influence the synchronization of its child elements. "a" elements may not be nested. An "a" element must have an href attribute.

Attributes

The "a" element can have the following attributes:

id
Defined in Section 2
href
This attribute contains the URI of the link's destination.
The "href" attribute is required for "a" elements.
show
This attribute controls the behavior of the source document containing the link when the link is followed. It can have one of the following values:

The default value of "show" is "replace".

title
Defined in Section 3.3.1
It  is strongly recommended that all "a" elements have a "title" attribute with a meaningful description. Authoring tools should ensure that no element can be introduced into a SMIL document without this attribute.

Element Content

The "a" element can contain the following children:

animation
Defined in Section 4.2.3
audio
Defined in Section 4.2.3
img
Defined in Section 4.2.3
par
Defined in Section 4.2.1
ref
Defined in Section 4.2.3
seq
Defined in Section 4.2.2
switch
Defined in Section 4.3
text
Defined in Section 4.2.3
textstream
Defined in Section 4.2.3
video
Defined in Section 4.2.3

Examples

Example 1

The link starts up the new presentation replacing the presentation that was playing.

<a href="http://www.cwi.nl/somewhereelse.smi">
     <video src="rtsp://foo.com/graph.imf" region="l_window"/>
</a>

In the example, the second line can be replaced by a reference to any valid subtree of an SMIL presentation.

Example 2

The link starts up the new presentation in addition to the presentation that was playing.

<a href="http://www.cwi.nl/somewhereelse.smi" show="new">
     <video src="rtsp://foo.com/graph.imf" region="l_window"/>
</a>

For example, this allows a SMIL player to spawn off an HTML browser.

Example 3

The link starts up the new presentation and pauses the presentation that was playing.

<a href="http://www.cwi.nl/somewhereelse.smi" show="pause">
     <video src="rtsp://foo.com/graph.imf" region="l_window"/>
</a>

Example 4

The following example contains a link from an element in one presentation A to the middle of another presentation B. This would play presentation B starting from the effective begin of the element with id "next".

Presentation A:

     <a href="http://www.cwi.nl/presentationB#next">
       <video src="rtsp://foo.com/graph.imf"/>
     </a>


Presentation B (http://www.cwi.nl/presentation):

      ...
      <seq>
        <video src="rtsp://foo.com/graph.imf"/>
        <par>
          <video src="rtsp://foo.com/timbl.rm" region="l_window"/>
          <video id="next" src="rtsp://foo.com/v1.rm" region="r_window"/>
                 ^^^^^^^^^
          <text src="rtsp://foo.com/caption1.html" region="l_2_title"/>
          <text src="rtsp://foo.com/caption2.rtx" region="r_2_title"/>
        </par>
      </seq>
      ...

4.5.2 The anchor Element

The functionality of the "a" element is restricted in that it only allows associating a link with a complete media object. HTML image maps have demonstrated that it is useful to associate links with spatial subparts of an object. The anchor element realizes similar functionality for SMIL:

  1. The anchor element allows associating a link destination to spatial and temporal subparts of a media object, using the "href" attribute (in contrast, the "a" element only allows associating a link with a complete media object).
  2. The anchor element allows making a subpart of the media object the destination of a link, using the "id" attribute.
  3. The anchor element allows breaking up an object into spatial subparts, using the "coords" attribute.
  4. The anchor element allows breaking up an object into temporal subparts, using the "begin" and "end" attributes. The values of the begin and end attributes are relative to the beginning of the media object.

Attributes

The anchor element can have the following attributes:

begin
Defined in Section 4.2.1
coords
The value of this attribute specifies a rectangle within the display area of a visual media object. Syntax and semantics of this attribute are similar to the coords attribute in HTML image maps, when the link is associated with a rectangular shape. The rectangle is specified by four length values: The first two values specify the coordinates of the upper left corner of the rectangle.The second two values specify the coordinates of the lower right corner of the rectangle. Coordinates are relative to the top left corner of the visual media object (see Figure 4.5). If a coordinate is specified as a percentage value, it is relative to the total width or height of the media object display area.
An attribute with an erroneous coords value is ignored (right-x smaller or equal to left-x, bottom-y smaller or equal to top-y). If the rectangle defined by the coords attribute exceeds the area covered by the media object, exceeding height and width are clipped at the borders of the media object.
Values of the coords attribute have the following syntax:
coords-value ::= left-x "," top-y "," right-x "," bottom-y


semantics of coords attribute D


Figure 4.5: Semantics of "coords" attribute

end
Defined in Section 4.2.1
id
Defined in Section 2
show
Defined in Section 4.5.1
skip-content
Defined in Section 3.3.1
title
Defined in Section 3.3.1
It  is strongly recommended that all anchor elements have a "title" attribute with a meaningful description. Authoring tools should ensure that no element can be introduced into a SMIL document without this attribute.

Examples

1) Associating links with spatial subparts

In the following example, the screenspace taken up by a video clip is split into two sections. A different link is associated with each of these sections.

<video src="http://www.w3.org/CoolStuff">
  <anchor href="http://www.w3.org/AudioVideo" coords="0%,0%,50%,50%"/>
  <anchor href="http://www.w3.org/Style"      coords="50%,50%,100%,100%"/>
</video>

2) Associating links with temporal subparts

In the following example, the duration of a video clip is split into two subintervals. A different link is associated with each of these subintervals.

<video src="http://www.w3.org/CoolStuff">
  <anchor href="http://www.w3.org/AudioVideo" begin="0s" end="5s"/>
  <anchor href="http://www.w3.org/Style"      begin="5s" end="10s"/>
</video>

3) Jumping to a subpart of an object

The following example contains a link from an element in one presentation A to the middle of a video object contained in another presentation B. This would play presentation B starting from second 5 in the video (i.e. the presentation would start as if the user had fast-forwarded the whole presentation to the point at which the designated fragment in the "CoolStuff" video begins).

Presentation A:

<a href="http://www.cwi.nl/mm/presentationB#tim">
   <video id="graph" src="rtsp://foo.com/graph.imf" region="l_window"/>
</a>


Presentation B:

<video src="http://www.w3.org/CoolStuff">
  <anchor id="joe" begin="0s" end="5s"/>
  <anchor id="tim" begin="5s" end="10s"/>
</video>

4) Combining different uses of links

The following example shows how the different uses of associated links can be used in combination.

Presentation A:

<a href="http://www.cwi.nl/mm/presentationB#tim">
  <video id="graph" src="rtsp://foo.com/graph.imf" region="l_window"/>
</a>


Presentation B:

<video src="http://www.w3.org/CoolStuff">
  <anchor id="joe" begin="0s" end="5s" coords="0%,0%,50%,50%"
          href="http://www.w3.org/"/>
  <anchor id="tim" begin="5s" end="10s" coords="0%,0%,50%,50%"
          href="http://www.w3.org/Tim"/>
</video>

5 SMIL DTD

5.1 Relation to XML

A SMIL 1.0 document may optionally contain a document type declaration, which names the document type definition (DTD) in use for the document. For SMIL, the document type declaration should look as follows (the double quotes can be replaced by single quotes):

<!DOCTYPE smil PUBLIC "-//W3C//DTD SMIL 1.0//EN"
               "http://www.w3.org/TR/REC-smil/SMIL10.dtd">

The XML 1.0 specification provides a way to extend the DTD using the <!DOCTYPE> element, for instance to add a new set of entity definitions. Authors must not use this feature with SMIL since many SMIL players will not support it.

The following is illegal in SMIL:

<!DOCTYPE smil PUBLIC "-//W3C//DTD SMIL 1.0//EN"
               "http://www.w3.org/TR/REC-smil/SMIL10.dtd" [
<!ENTITY % AcmeCorpSymbols PUBLIC
     "-//Acme Corp//ENTITIES Corporate Symbols//EN"
     "http://www.acme.com/corp_symbols.xml"
>
%AcmeCorpSymbols;
]>

5.2 DTD

<!--

    This is the XML document type definition (DTD) for SMIL 1.0.

    Date: 1998/06/15 08:56:30

    Authors: 
        Jacco van Ossenbruggen <jrvosse@cwi.nl> 
        Sjoerd Mullender       <sjoerd@cwi.nl>
        
    Further information about SMIL is available at:

          http://www.w3.org/AudioVideo/

-->

<!-- Generally useful entities -->
<!ENTITY % id-attr "id ID #IMPLIED">
<!ENTITY % title-attr "title CDATA #IMPLIED">
<!ENTITY % skip-attr "skip-content (true|false) 'true'">
<!ENTITY % desc-attr "
        %title-attr;
        abstract        CDATA   #IMPLIED
        author          CDATA   #IMPLIED
        copyright       CDATA   #IMPLIED
">

<!--=================== SMIL Document =====================================-->
<!--
     The root element SMIL contains all other elements.
-->
<!ELEMENT smil (head?,body?)>
<!ATTLIST smil
        %id-attr;
>

<!--=================== The Document Head =================================-->
<!ENTITY % layout-section "layout|switch">

<!ENTITY % head-element "(meta*,((%layout-section;), meta*))?">

<!ELEMENT head %head-element;>
<!ATTLIST head %id-attr;>


<!--=================== Layout Element ====================================-->
<!--
     Layout contains the region and root-layout elements defined by
     smil-basic-layout or other elements defined an external layout 
     mechanism.
-->
<!ELEMENT layout ANY>
<!ATTLIST layout
        %id-attr;
        type CDATA      "text/smil-basic-layout"
>


<!--=================== Region Element ===================================-->
<!ENTITY % viewport-attrs "
        height              CDATA    #IMPLIED
        width               CDATA    #IMPLIED
        background-color    CDATA    #IMPLIED
">

<!ELEMENT region EMPTY>
<!ATTLIST region
        %id-attr;
        %title-attr;
        %viewport-attrs;
        left                CDATA    "0"
        top                 CDATA    "0"
        z-index             CDATA    "0"
        fit                 (hidden|fill|meet|scroll|slice)    "hidden"
        %skip-attr;
>

<!--=================== Root-layout Element ================================-->
<!ELEMENT root-layout EMPTY>
<!ATTLIST root-layout
        %id-attr;
        %title-attr;
        %viewport-attrs;
        %skip-attr;
>


<!--=================== Meta Element=======================================-->
<!ELEMENT meta EMPTY>
<!ATTLIST meta
        name    NMTOKEN #REQUIRED
        content CDATA   #REQUIRED
        %skip-attr;
>

<!--=================== The Document Body =================================-->
<!ENTITY % media-object "audio|video|text|img|animation|textstream|ref">
<!ENTITY % schedule "par|seq|(%media-object;)">
<!ENTITY % inline-link "a">
<!ENTITY % assoc-link "anchor">
<!ENTITY % link "%inline-link;">
<!ENTITY % container-content "(%schedule;)|switch|(%link;)">
<!ENTITY % body-content "(%container-content;)">

<!ELEMENT body (%body-content;)*>
<!ATTLIST body %id-attr;>

<!--=================== Synchronization Attributes ========================-->
<!ENTITY % sync-attributes "
        begin   CDATA   #IMPLIED
        end     CDATA   #IMPLIED
">

<!--=================== Switch Parameter Attributes =======================-->
<!ENTITY % system-attribute "
        system-bitrate             CDATA                #IMPLIED
        system-language            CDATA                #IMPLIED
        system-required            NMTOKEN              #IMPLIED
        system-screen-size         CDATA                #IMPLIED
        system-screen-depth        CDATA                #IMPLIED
        system-captions            (on|off)             #IMPLIED
        system-overdub-or-caption  (caption|overdub)    #IMPLIED
">

<!--=================== Fill Attribute ====================================-->
<!ENTITY % fill-attribute "
        fill    (remove|freeze)    'remove'
">


<!--=================== The Parallel Element ==============================-->
<!ENTITY % par-content "%container-content;">
<!ELEMENT par    (%par-content;)*>
<!ATTLIST par
        %id-attr;
        %desc-attr;
        endsync CDATA           "last"
        dur     CDATA           #IMPLIED
        repeat  CDATA           "1"
        region  IDREF           #IMPLIED
        %sync-attributes;
        %system-attribute;
>

<!--=================== The Sequential Element ============================-->
<!ENTITY % seq-content "%container-content;">
<!ELEMENT seq    (%seq-content;)*>
<!ATTLIST seq
        %id-attr;
        %desc-attr;
        dur     CDATA           #IMPLIED
        repeat  CDATA           "1"
        region  IDREF           #IMPLIED
        %sync-attributes;
        %system-attribute;
>

<!--=================== The Switch Element ================================-->
<!-- In the head, a switch may contain only layout elements,
     in the body, only container elements. However, this
     constraint cannot be expressed in the DTD (?), so
     we allow both:
-->
<!ENTITY % switch-content "layout|(%container-content;)">
<!ELEMENT switch (%switch-content;)*>
<!ATTLIST switch
        %id-attr;
        %title-attr;
>

<!--=================== Media Object Elements =============================-->
<!-- SMIL only defines the structure. The real media data is
     referenced by the src attribute of the media objects.
-->

<!-- Furthermore, they have the following attributes as defined
     in the SMIL specification:
-->
<!ENTITY % mo-attributes "
        %id-attr;
        %desc-attr;
        region     IDREF           #IMPLIED
        alt        CDATA           #IMPLIED
        longdesc   CDATA           #IMPLIED
        src        CDATA           #IMPLIED
        type       CDATA           #IMPLIED
        dur        CDATA           #IMPLIED
        repeat     CDATA           '1'
        %fill-attribute;
        %sync-attributes;
        %system-attribute;
">

<!--
     Most info is in the attributes, media objects are empty or
     contain associated link elements:
-->
<!ENTITY % mo-content "(%assoc-link;)*">
<!ENTITY % clip-attrs "
        clip-begin      CDATA   #IMPLIED
        clip-end        CDATA   #IMPLIED
">

<!ELEMENT ref           %mo-content;>
<!ELEMENT audio         %mo-content;>
<!ELEMENT img           %mo-content;>
<!ELEMENT video         %mo-content;>
<!ELEMENT text          %mo-content;>
<!ELEMENT textstream    %mo-content;>
<!ELEMENT animation     %mo-content;>

<!ATTLIST ref           %mo-attributes; %clip-attrs;>
<!ATTLIST audio         %mo-attributes; %clip-attrs;>
<!ATTLIST video         %mo-attributes; %clip-attrs;>
<!ATTLIST animation     %mo-attributes; %clip-attrs;>
<!ATTLIST textstream    %mo-attributes; %clip-attrs;>
<!ATTLIST text          %mo-attributes;>
<!ATTLIST img           %mo-attributes;>

<!--=================== Link Elements =====================================-->

<!ENTITY % smil-link-attributes "
        %id-attr;
        %title-attr;
        href            CDATA                   #REQUIRED
        show            (replace|new|pause)     'replace'
">


<!--=================== Inline Link Element ===============================-->
<!ELEMENT a (%schedule;|switch)*>
<!ATTLIST a
        %smil-link-attributes;
>


<!--=================== Associated Link Element ===========================-->
<!ELEMENT anchor EMPTY>
<!ATTLIST anchor
        %skip-attr;
        %smil-link-attributes;
        %sync-attributes;
        coords          CDATA                   #IMPLIED
>

References

[CSS2]
"Cascading Style Sheets, level 2", B. Bos, H. Lie, C. Lilley, I. Jacobs, 12 May 1998.
Available at http://www.w3.org/TR/REC-CSS2/.
[HTML40]
"HTML 4.0 Specification", D. Raggett, A. Le Hors, I. Jacobs, 24 April 1998.
Available at http://www.w3.org/TR/REC-html40/.
[ISO/IEC 10646]
ISO (International Organization for Standardization). ISO/IEC 10646-1993 (E). Information technology -- Universal Multiple-Octet Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane. [Geneva]: International Organization for Standardization, 1993 (plus amendments AM 1 through AM 7).
[NAMESPACES]
"Namespaces in XML", T. Bray, D. Hollander, A. Layman, 27 March 1998
W3C working draft. Available at http://www.w3.org/TR/WD-xml-names.
[PICS]
"PICS 1.1 Label Distribution -- Label Syntax and Communication Protocols", 31 October 1996, T. Krauskopf, J. Miller, P. Resnick, W. Trees
Available at http://www.w3.org/TR/REC-PICS-labels-961031
[RFC1738]
"Uniform Resource Locators", T. Berners-Lee, L. Masinter, and M. McCahill, December 1994.
Available at ftp://ftp.isi.edu/in-notes/rfc1738.txt.
[RFC1766]
"Tags for the Identification of Languages", H. Alvestrand, March 1995.
Available at ftp://ftp.isi.edu/in-notes/rfc1766.txt.
[RFC1808]
"Relative Uniform Resource Locators", R. Fielding, June 1995.
Available at ftp://ftp.isi.edu/in-notes/rfc1808.txt.
[RFC2045]
"Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", N. Freed and N. Borenstein, November 1996.
Available at ftp://ftp.isi.edu/in-notes/rfc2045.txt. Note that this RFC obsoletes RFC1521, RFC1522, and RFC1590.
[SMPTE]
"Time and Control Codes for 24, 25 or 30 Frame-Per-Second Motion-Picture Systems - RP 136-1995".  Society of Motion Picture & Television Engineers.
[URI]
"Uniform Resource Identifiers (URI): Generic Syntax and Semantics", T. Berners-Lee, R. Fielding, L. Masinter, 4 March 1998.
Available at http://www.ics.uci.edu/pub/ietf/uri/draft-fielding-uri-syntax-02.txt. This is a work in progress that is expected to update [RFC1738] and [RFC1808].
[XML10]
"Extensible Markup Language (XML) 1.0", T. Bray, J. Paoli, C.M. Sperberg-McQueen, editors, 10 February 1998.
Available at http://www.w3.org/TR/REC-xml/

Appendix

Extending SMIL 1.0

(non-normative)

In the future, SMIL 1.0 may be extended by another W3C recommendation, or by private extensions.

For these extensions, it is recommended that the following rules are obeyed:

It is recommended that SMIL 1.0 players are prepared to handle documents that contain extension that obey these two rules.

Extensions should be handled using an XML namespace mechanism, once such a mechanism becomes a W3C recommendation. In the rest of the section, the syntax and semantics for XML namespaces defined in the W3C note [NAMESPACE] will be used for demonstration purposes only.

The following cases can occur:

  1. The document contains a namespace declaration for the SMIL 1.0 specification that defines an empty prefix. In this case, non-SMIL 1.0 elements and attributes are only allowed in a document if they are declared using an XML namespace. The document may not contain a document type declaration for SMIL 1.0. If it does, it is invalid.
    In the following example, the element "new:a" is a legal extension. The elements "mytags:a" and "b" are syntax errors, since they are not declared using an XML namespace.
    <?xml:namespace ns="http://www.acme.com/new-smil" prefix="new" ?>
    <?xml:namespace ns="http://www.w3.org/TR/PR-smil" ?>
    <smil>
      <body>
        <par>
          <new:a>
          ...
          </new:a>
          <mytags:a ... />
            ...
          </mytags:a>
    <b> ... </b> </par> </body> </smil>
  2. The document contains no document type declaration, it contains a document type declaration for a SMIL version higher than 1.0, or it contains a namespace declaration for a SMIL specification with a version higher than 1.0. For a SMIL 1.0 player to be able to recognize such a namespace declaration, it is recommended that the URI of future SMIL versions starts with http://www.w3.org/TR/REC-smil, and is followed by more characters which may for example be a version number.
    In this case, a SMIL 1.0 player should assume that it is processing a SMIL document with a version number higher than 1.0.
    The following cases can occur:
    Unknown element
    Unknown elements are ignored
    An unknown element may contain content that consists of SMIL 1.0 elements. Whether such content is ignored or processed depends on the value of the "skip-content" attribute. If the attribute is set to "true", or the attribute is absent, the content is not processed. If it is set to "false", the content is processed.
    Content in Element that was declared "Empty"
    A future version of SMIL may allow content in elements that are declared as "empty" in SMIL 1.0.
    Whether this content is ignored or not depends on the value of the "skip-content" attribute of the formerly empty element. If the attribute is set to "true", the content is not processed. If it is set to "false", the content is processed.
    Unknown Attribute
    Unknown attributes are ignored.
    Unknown Attribute Value
    Attributes with unknown attribute values are ignored.
  3. The document contains a document type declaration for SMIL 1.0. In this case, it may not contain any non-SMIL 1.0 elements, even if they are declared using XML namespaces. This is because such extensions would render the document invalid.

Using SMIL 1.0 as an Extension

When the XML namespace mechanism is used to include SMIL elements and attributes in other XML-based documents, it is recommended to use the following namespace identifier: http://www.w3.org/TR/REC-smil