Network Working Group                                         P. Hoschka
INTERNET DRAFT                                                       W3C
draft-hoschka-smil-media-type-10.txt                          March 2002


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


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

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   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet- Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

Abstract

   This document specifies the Media Type for version 1 and version 2 of
   the Synchronized Multimedia Integration Language (SMIL 1.0 and SMIL
   2.0). SMIL allows integrating a set of independent multimedia objects
   into a synchronized multimedia presentation.

1.  Introduction

   The World Wide Web Consortium has issued specifications which define
   version 1 [1] and version 2 [2] 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 [3]. Before using the "application/smil"
   or "application/smil+xml" media type, implementors must thus be
   familiar with [3].




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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

   MIME media type name: application

   MIME subtype name: smil

   Required parameters: none

   Optional parameters:

   charset

   All of the considerations described in RFC3023 also apply to the SMIL
   media type.

   profile

   See Section 5 of this document.

   Encoding considerations:

   All of the considerations described in RFC3023 also apply to the SMIL
   media type.

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



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   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.

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] and [2]

Applications which use this media type:

   SMIL players and editors

Additional information:

   Semantics of fragment identifiers in URIs: The SMIL media type allows
   to append a fragment identifier 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 [2].

Magic number(s):

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



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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: COMMON

Author/Change controller:

   The SMIL 1.0 and SMIL 2.0 specifications are a work product of the
   World Wide Web Consortium's SYMM Working Group.

   The W3C has change control over both specifications.

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 registration of application/smil

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

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



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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: see registration of application/smil

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 also 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/PR/Language"'.

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+smil MIME type
   registration [4], 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
   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 CC/PP framework [5]. It is suggested that



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   the "profile" parameter be used until the CC/PP framework 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/REC/HostLanguage"

6.  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
        Specification", W3C Recommendation,
        http://www.w3.org/TR/smil20/, August 2001.
   [3]  M. Murata, S. St.Laurent, D. Kohn E. "XML Media Types", RFC 3023,
        January 2001.
   [4]  M. Baker. "The 'application/xhtml+xml' Media Type", Internet Draft
        draft-baker-xhtml-media-reg-01.txt, February 2001.
   [5]  G. Klyne, F. Reynolds, C. Woodrow, H. Ohto. "Composite Capability/
        Preferences Profiles (CC/PP): Structure and Vocabularies", W3C
        Working Draft http://www.w3.org/TR/CCPP-struct-vocab/, March 2001.

6.  Author's Address

   Philipp Hoschka
   W3C/INRIA
   2004, route des Lucioles - B.P. 93
   06902 Sophia Antipolis Cedex
   FRANCE

   Phone: +33 (0)492387984
   Fax:+33 (0)493657765
   EMail: ph@w3.org















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