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Network Working Group                                         P. HoschkaRequest for Comments: 4536                                           W3CCategory: Informational                                         May 2006The application/smil and application/smil+xml Media TypesStatus of This Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2006).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 (W3C) has issued specifications that   define versions 1.0 [1], 2.0 [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 onRFC 3023, which defines 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, and   4. define conditional content inclusion/exclusion based on      system/network properties.Hoschka                      Informational                      [Page 1]

RFC 4536       application/smil and application/smil+xml        May 20063.  Registration Information3.1.  Registration of MIME media type application/smil   MIME media type name: application   MIME subtype name: smil   Required parameters: none   Optional parameters:      charset         Same as charset parameter considerations of application/xml inRFC 3023.      profile         SeeSection 5 of this document.   Encoding considerations:      Same as encoding considerations of application/xml inRFC 3023   Security considerations: SeeSection 6, "Security Considerations", of   this document.   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 editorsHoschka                      Informational                      [Page 2]

RFC 4536       application/smil and application/smil+xml        May 2006   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 SMIL files.  However,Section 4 of this document 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.Hoschka                      Informational                      [Page 3]

RFC 4536       application/smil and application/smil+xml        May 20063.2.  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: SeeSection 6, "Security Considerations", of   this document   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.   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.Hoschka                      Informational                      [Page 4]

RFC 4536       application/smil and application/smil+xml        May 20064.  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 that 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 the relevant 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 targeted 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   language specification.   For example, user agents supporting only SMIL Basic (seehttp://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 the future, the functionality afforded by this parameter will also   be achievable by the emerging work on a protocol to transfer   Composite Capability/Preferences Profiles (CC/PP) descriptions [6].   It is suggested that the "profile" parameter be used until the CC/PP   protocol work has been finalized.Hoschka                      Informational                      [Page 5]

RFC 4536       application/smil and application/smil+xml        May 2006   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, etc.), 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 ensures that 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, it 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 ofRFC 3023 also   apply to SMIL.Hoschka                      Informational                      [Page 6]

RFC 4536       application/smil and application/smil+xml        May 20067.  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]  Murata, M., St. Laurent, S., and D. Kohn, "XML Media Types",RFC3023, January 2001.8.  Informative References   [5]  Baker, M. and 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 Recommendationhttp://www.w3.org/TR/CCPP-struct-vocab/, January 2004.Author's Address   Philipp Hoschka   W3C/ERCIM   2004, route des Lucioles - B.P. 93   06902 Sophia Antipolis Cedex   FRANCE   EMail: ph@w3.orgHoschka                      Informational                      [Page 7]

RFC 4536       application/smil and application/smil+xml        May 2006Full Copyright Statement   Copyright (C) The Internet Society (2006).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is provided by the IETF   Administrative Support Activity (IASA).Hoschka                      Informational                      [Page 8]