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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 RFC 4536

Network Working Group                                         P. Hoschka
INTERNET DRAFT                                                       W3C
draft-hoschka-smil-media-type-13.txt                       February 2006


       The application/smil and application/smil+xml Media Types


   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

Abstract

   This document specifies the Media Type for versions 1.0, 2.0 and 2.1
   of the Synchronized Multimedia Integration Language (SMIL 1.0, SMIL
   2.0, SMIL 2.1).  SMIL allows integration of a set of independent
   multimedia objects into a synchronized multimedia presentation.

1.  Introduction

   The World Wide Web Consortium has issued specifications which define
   versions 1 [1], 2 [2] and 2.1 [3] of  the Synchronized Multimedia
   Integration Language (SMIL). This memo provides information about the
   application/smil and application/smil+xml Media Types.

   The definition is based on RFC3023 defining the use of the
   "application/xml" media type [4]. Before using the "application/smil"
   or "application/smil+xml" media type, implementors must thus be
   familiar with [4].

2.  Synchronized Multimedia Integration Language

   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
   4.define conditional content inclusion/exclusion based on
   system/network properties

3.  Registration Information

   To: ietf-types@iana.org
   Subject: Registration of MIME media type application/smil




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   MIME media type name: application

   MIME subtype name: smil

   Required parameters: none

   Optional parameters:

   charset

   Same as charset parameter considerations of application/xml in RFC
   3023

   profile

   See Section 5 of this document.

   Encoding considerations:

   Same as encoding considerations of application/xml in RFC 3023

Security considerations: see Section "6. Security Considerations" below

Interoperability considerations:

   SMIL documents contain links to other media objects. The SMIL player
   must be able to decode the media types of these media in order to
   display the whole document. To increase interoperability, SMIL has
   provisions for including alternate versions of a media object in a
   document.

Published specification: see [1], [2] and [3]

Applications which use this media type:

   SMIL players and editors

Additional information:

   Semantics of fragment identifiers in URIs: The SMIL media type allows
   a fragment identifier to be appended to a URI pointing to a SMIL
   resource (e.g. http://www.example.com/test.smil#foo).  The semantics
   of fragment identifiers for SMIL resources are defined in the SMIL
   specification.

Magic number(s):

   There is no single initial byte sequence that is always present for



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   SMIL files. However, Section 4 below gives some guidelines for
   recognizing SMIL files.

File extension(s): .smil, .smi, .sml

NOTE: On the Windows operating system and the Macintosh
platform, the ".smi" extension is used by other formats.
To avoid conflicts, it is thus recommended to use the extension
".smil" for storing SMIL files on these platforms.

Macintosh File Type Code(s): "TEXT", ".SMI", "SMIL"
Object Identifier(s) or OID(s): none

Person & email address to contact for further information:

The author of this memo.

Intended usage: OBSOLETE

Author/Change controller:

   The SMIL specification is a work product of the World Wide Web
   Consortium's SYMM Working Group.

   The W3C has change control over the specification.

To: ietf-types@iana.org
Subject: Registration of MIME media type application/smil+xml

MIME media type name: application

MIME subtype name: smil+xml

Required parameters: see registration of application/smil

Optional parameters: see registration of application/smil

Encoding considerations: see registration of application/smil

Security considerations: see Section "6. Security Considerations" below

Interoperability considerations: see registration of application/smil

Published specification: see registration of application/smil

Applications which use this media type: see registration of
application/smil




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Additional information: see registration of application/smil

Magic number(s): see registration of application/smil

File extension(s): see registration of application/smil

Macintosh File Type Code(s): see registration of application/smil

Object Identifier(s) or OID(s): see registration of application/smil

Person & email address to contact for further information: see
registration of application/smil

Intended usage: COMMON

Author/Change controller: see registration of application/smil

4. Recognizing SMIL files

   All SMIL files will have the string "<smil" near the beginning of the
   file.  Some will also begin with an XML declaration which begins with
   "<?xml", though that alone does not indicate a SMIL document.

   All SMIL 2.0 files must include a declaration of the SMIL 2.0
   namespace.  This should appear shortly after the string "<smil", and
   should read 'xmlns="http://www.w3.org/2001/SMIL20/Language"'.

   All SMIL 2.1 files must include a declaration of a SMIL 2.1
   namespace, appearing shortly after the string "<smil". The namespace
   string depends on the language profile. Please refer to the SMIL 2.1
   specification for the definition of therelevant namespace names.

5. The "profile" optional parameter

   This parameter is meant to be used in MIME media type based content
   negotiation (such as that done with the HTTP "Accept" header) to
   negotiate for a variety of SMIL based languages. It is modelled after
   the "profile" parameter in the application/xhtml+xml MIME type
   registration [5], and is motivated by very similar considerations.

   The parameter is intended to be used only during content negotiation.
   It is not expected that it be used to deliver content, or that origin
   web servers have any knowledge of it (though they are welcome to).
   It is primarily targetted for use on the network by proxies in the
   HTTP chain that manipulate data formats (such as transcoders).

   The value of the profile attribute is a URI that can be used as a
   name to identify a language.  Though the URI need not be resolved in



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   order to be useful as a name, it could be a namespace, schema, or a
   language specification.

   As an example, user agents supporting only SMIL Basic (see
   http://www.w3.org/TR/smil20/smil-basic.html) currently have no
   standard means to convey their inability to fully support SMIL 2.0.
   While SMIL 2.0 Basic user agents are required to parse the full SMIL
   2.0 language, there is potentially a substantial burden in receiving
   and parsing document content that will not be presented to the user,
   since its functionality is not included in SMIL Basic.

   In future, the functionality afforded by this parameter will also be
   achievable by the emerging work on a protocol to transfer CC/PP
   descriptions [6]. It is suggested that the "profile" parameter be
   used until the CC/PP protocol work has been finalized.

   An example use of this parameter as part of a HTTP GET transaction
   would be:

        Accept: application/smil+xml;
           profile="http://www.w3.org/2001/SMIL20/HostLanguage"

6. Security Considerations

   SMIL documents contain a construct that allows "infinite loops".
   This is indispensable for a multimedia format. However, SMIL clients
   should foresee provisions such as a "stop" button that lets users
   interrupt such an "infinite loop".

   As with HTML, SMIL documents contain links to other media
   (images,sounds, videos, text, ...) and those links are typically
   followed automatically by software, resulting in the transfer of
   files without the explicit request of the user for each one. The
   security considerations of each linked file are those of the
   individual registered types.

   The SMIL language contains "switch" elements. SMIL provides no
   mechanism that assures the media objects contained in a "switch"
   element provide equivalent information. An author knowing that one
   SMIL player will display one alternative of a "switch" and another
   will display a different part, can put different information in the
   two parts. While there are legitimate use cases for this, this also
   gives rise to a security consideration: The author can fool viewers
   into thinking that the same information was displayed when in fact it
   was not.

   In addition, all of the security considerations of RFC3023 also apply
   to SMIL.



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7. Normative References

   [1]  "Synchronized Multimedia Integration Language (SMIL) 1.0
        Specification", W3C Recommendation REC-smil-19980615,
        http://www.w3.org/TR/1998/REC-smil/, July 1998.
   [2] "Synchronized Multimedia Integration Language (SMIL 2.0) -
       [Second Edition]", W3C Recommendation,
        http://www.w3.org/TR/2005/REC-SMIL2-20050107/, January 2005.
   [3] "Synchronized Multimedia Integration Language (SMIL 2.1)",
        W3C Recommendation,
        http://www.w3.org/TR/2005/REC-SMIL2-20051213/, December 2005.
   [4]  M. Murata, S. St.Laurent, D. Kohn E. "XML Media Types", RFC 3023,
        January 2001.

8. Non-normative References

   [5]  M. Baker, P. Stark. "The 'application/xhtml+xml' Media Type", RFC 3236,
        January 2002.
   [6]  H. Ohto, J. Hjelm, G. Klyne, M. Butler, L. Tran, F. Reynolds, C. Woodrow
        "Composite Capability/Preferences Profiles (CC/PP): Structure and
        Vocabularies 1.0", W3C Recommendation
        http://www.w3.org/TR/CCPP-struct-vocab/, January 2004.

8.  Author's Address

   Philipp Hoschka
   W3C/ERCIM
   2004, route des Lucioles - B.P. 93
   06902 Sophia Antipolis Cedex
   FRANCE
   EMail: ph@w3.org

   Copyright (C) The Internet Society (2006)

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   FOR A PARTICULAR PURPOSE.

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