Movatterモバイル変換


[0]ホーム

URL:


previous  next  contents  

8.The SMIL 2.1 Metainformation Module

Editor for SMIL 2.1:
Thierry Michel, W3C.
Editor for SMIL 2.0:
Thierry Michel, W3C.

Table of contents

8.1 Summary of Changes for SMIL 2.1

This section is informative.

The SMIL 2.1 specification leaves the SMIL 2.0 Metainformation Module[SMIL20-meta] unchanged.

8.2Introduction

This section is informative.

This section defines the SMIL 2.1 Metainformation Module composed of asingle module. This module contains elements and attributes that allowdescription of SMIL documents.
Since these elements and attributes are defined in a module, designers ofother markup languages can choose whether or not to include thisfunctionality in their languages.

The World Wide Web was originally built for human consumption, andalthough everything on it is machine-readable, this data is notmachine-understandable. It is very hard to automate anything on the Web, andbecause of the volume of information the Web contains, it is not possible tomanage it manually. Metadata is "data about data" (for example, a librarycatalog is metadata, since it describes publications) or specifically in thecontext of this specification "data describing Web resources".
The solution proposed here is to use metadata information to describe SMILdocuments published on the Web.

The earlier SMIL 1.0 specification allowed authors to describe documentswith a very basic vocabulary using themeta element.
The SMIL 2.1 Metainformation module defined in this specification fullysupports the use of thismetaelement from SMIL 1.0 but it also introduces new capabilities for describingmetadata using the Resource Description Framework Model and Syntax[RDFsyntax], a powerful meta information languagefor providing information about resources.

8.3 Overview of the SMIL 2.1 Metainformation module

This section is informative.

8.3.1Compatibility with SMIL 1.0

To insure backward compatibility with SMIL 1.0, themeta element as specified in the SMIL 1.0[SMIL10] Recommendation can be used todefine properties of a document (e.g., author/creator, expiration date, alist of key words, etc.) and assign values to those properties.

8.3.2Extensions to SMIL 1.0

SMIL 2.1 extends SMIL 1.0 meta information functionalities with the newmetadataelement to host RDFstatements as RDF provides a more general treatment of metadata.
RDF is a declarative language and provides a standard way for using XML torepresent metadata in the form of statements about properties andrelationships of items on the Web. Such items, known as resources, can bealmost anything, provided it has a Web address. This means that you canassociate metadata information with a SMIL document, but also a graphic, anaudio file, a movie clip, and so on.

RDF is the appropriate language for metadata. The specifications for RDFcan be found at:

Metadata information within an SMIL 2.1 document should be expressed inthe appropriate RDF namespaces[XML-NS] andshould be placed within themetadata element. (Seeexample below.)

8.3.3 Multiple description schemes

RDF appears to be the ideal approach for supporting descriptors frommultiple description schemes simultaneously.

Here are some suggestions for content creators regarding metadata:

8.4 SMIL 2.1 Metainformation Module Syntax and Semantics

This section defines the elements and attributes that make up thefunctionality in the SMIL Metainformation module.

8.4.1 Themeta element

Element definition

Themeta element is an emptyelement.
Eachmeta element specifies a singleproperty/value pair in the name and content attributes, respectively.

Attribute definitions
content = CDATA
This attribute specifies a property's value. This specification does not list legal values for this attribute.
Thecontent attribute is required formeta elements.
name =CDATA
This attribute identifies a property name. Thename attribute is required formeta elements. The list of properties for the name attribute 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.
    Note: SMIL 2.1 deprecates the base property in favor of the more general XML base url mechanisms currently being completed[XMLBase]. The language profile is responsible for specifying which of these technologies are specifically supported.
  • 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 specifies the title of the presentation.

8.4.2 Themetadataelement

Element definition

Themetadata element containsinformation that is also related to meta information of the document. It actsas the root element of the RDF tree. Themetadata element can contain thefollowing child elements:

RDF element and its sub-elements (refer to W3Cmetadata Recommendations[RDFsyntax]).

8.5An Example

This section is informative.

Here is an example of how metadata can be included in an SMIL document.The example uses the Dublin Core version 1.0 RDF schema[DC]and an hypothetic SMIL metadata RDFSchema:

<?xml version="1.1" ?><smil xmlns="http://www.w3.org/2005/SMIL21/Language">     <head> <meta name="Publisher" content="W3C" /> <meta name="Date" content="1999-10-12" /> <meta name="Rights" content="Copyright 1999 John Smith" /> <meta http-equiv="Expires" content=" 31 Dec 2001 12:00:00 GMT"/>  <metadata>   <rdf:RDF       xmlns:rdf = "http://www.w3.org/1999/02/22-rdf-syntax-ns#"       xmlns:rdfs = "http://www.w3.org/2000/01/rdf-schema#"       xmlns:dc = "http://purl.org/dc/elements/1.1/"       xmlns:smilmetadata = "http://www.example.org/AudioVideo/.../smil-ns#" ><!-- Metadata about the SMIL presentation -->   <rdf:Description rdf:about="http://www.example.com/meta.smi"       dc:Title="An Introduction to the Resource Description Framework"       dc:Description="The Resource Description Framework (RDF) enables the encoding, exchange and reuse of structured metadata"       dc:Publisher="W3C"       dc:Date="1999-10-12"       dc:Rights="Copyright 1999 John Smith"       dc:Format="text/smil" >                       <dc:Creator>          <rdf:Seq rdf:ID="CreatorsAlphabeticalBySurname">             <rdf:li>Mary Andrew</rdf:li>             <rdf:li>Jacky Crystal</rdf:li>          </rdf:Seq>       </dc:Creator>       <smilmetadata:ListOfVideoUsed>          <rdf:Seq rdf:ID="VideoAlphabeticalByFormatname">              <rdf:li rdf:resource="http://www.example.com/videos/meta-1999.mpg"/>              <rdf:li rdf:resource="http://www.example.com/videos/meta2-1999.mpg"/>           </rdf:Seq>       </smilmetadata:ListOfVideoUsed>       <smilmetadata:Access smilmetadata:LevelAccessibilityGuidelines="AAA"/>   </rdf:Description><!-- Metadata about the video -->   <rdf:Description rdf:about="http://www.example.com/videos/meta-1999.mpg"        dc:Title="RDF part one"        dc:Creator="John Smith"        dc:Subject="Metadata,RDF"        dc:Description="RDF basic functionalities"        dc:Publisher="W3C Press Service"        dc:Format="video/mpg"        dc:Language="en"        dc:Date="1999-10-12"        smilmetadata:Duration="60 secs"        smilmetadata:VideoCodec="MPEG2" >        <smilmetadata:ContainsSequences>           <rdf:Seq rdf:ID="ChronologicalSequences">             <rdf:li rdf:resource="http://www.example.com/videos/meta-1999.mpg#scene1"/>             <rdf:li rdf:resource="http://www.example.com/videos/meta-1999.mpg#scene2"/>            </rdf:Seq>         </smilmetadata:ContainsSequences>   </rdf:Description><!-- Metadata about a scene of the video -->   <rdf:Description rdf:about="#scene1"        dc:Title="RDF intro"        dc:Description="Introduction to RDF functionalities"        dc:Language="en"        smilmetadata:Duration="30 secs"        smilmetadata:Presenter="David Jones" >        <smilmetadata:ContainsShots>           <rdf:Seq rdf:ID="ChronologicalShots">             <rdf:li>Panorama-shot</rdf:li>             <rdf:li>Closeup-shot</rdf:li>           </rdf:Seq>        </smilmetadata:ContainsShots>   </rdf:Description>  </rdf:RDF> </metadata><!-- SMIL presentation --> <layout>    <region top="5" /> </layout> </head> <body>   <video region="a" src="/videos/meta-1999.mpg" >     <area begin="0s" end ="30s"/>     <area begin="30s" end ="60s"/>   </video>   <video region="a" src="/videos/meta2-1999.mpg"/> </body></smil>

previous  next  contents  

[8]ページ先頭

©2009-2025 Movatter.jp