Network Working Group P. HoschkaINTERNET DRAFTRequest for Comments: 4536 W3C Category: Informational May 2006 The application/smil and application/smil+xml Media TypesBy submitting this Internet-Draft, each author represents that any applicable patent or other IPR claimsStatus ofwhich he or she is aware have been or will be disclosed, and anyThis Memo This memo provides information for the Internet community. It does not specify an Internet standard ofwhich he or she becomes aware will be disclosed, in accordance with Section 6any kind. Distribution ofBCP 79.this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document specifies theMedia Typemedia type for versions 1.0,2.02.0, 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 specificationswhichthat define versions11.0 [1],22.0 [2] and 2.1 [3] of the Synchronized Multimedia Integration Language (SMIL). This memo provides information about the application/smil and application/smil+xmlMedia Types.media types. The definition is based onRFC3023 definingRFC 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 can1.describe1. describe the temporal behavior of thepresentation 2.describepresentation, 2. describe the layout of the presentation on ascreen 3.associatescreen, 3. associate hyperlinks with mediaobjects 4.defineobjects, and 4. define conditional content inclusion/exclusion based on system/networkpropertiesproperties. 3. Registration InformationTo: ietf-types@iana.org Subject:3.1. 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 in RFC30233023. profile See Section 5 of this document. Encoding considerations: Same as encoding considerations of application/xml in RFC 3023 Security considerations:seeSee Section"6. Security Considerations" below6, "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:seeSee [1],[2][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.(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 4belowof 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.To: ietf-types@iana.org Subject:3.2. Registration of MIME media type application/smil+xml MIME media type name: application MIME subtype name: smil+xml Required parameters:seeSee registration ofapplication/smilapplication/smil. Optional parameters:seeSee registration ofapplication/smilapplication/smil. Encoding considerations:seeSee registration ofapplication/smilapplication/smil. Security considerations:seeSee Section"6. Security Considerations" below6, "Security Considerations", of this document Interoperability considerations:seeSee registration ofapplication/smilapplication/smil. Published specification:seeSee registration ofapplication/smilapplication/smil. Applications which use this media type:seeSee registration ofapplication/smilapplication/smil. Additional information:seeSee registration ofapplication/smilapplication/smil. Magic number(s):seeSee registration ofapplication/smilapplication/smil. File extension(s):seeSee registration ofapplication/smilapplication/smil. Macintosh File Type Code(s):seeSee registration ofapplication/smilapplication/smil. Object Identifier(s) or OID(s):seeSee registration ofapplication/smilapplication/smil. Person & email address to contact for further information:seeSee registration ofapplication/smilapplication/smil. Intended usage: COMMON Author/Change controller:seeSee registration ofapplication/smilapplication/smil. 4. Recognizing SMILfilesFiles All SMIL files will have the string "<smil" near the beginning of the file. Some will also begin with an XML declarationwhichthat 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 oftherelevantthe relevant namespace names. 5. The "profile"optional parameterOptional Parameter This parameter is meant to be used in MIMEmedia type basedmedia-type-based content negotiation (such as that done with the HTTP "Accept" header) to negotiate for a variety ofSMIL basedSMIL-based languages. It is modelled after the "profile" parameter in the application/xhtml+xml MIME type registration[5],[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 primarilytargettedtargeted 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, oralanguage specification.As anFor 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 the future, the functionality afforded by this parameter will also be achievable by the emerging work on a protocol to transferCC/PPComposite 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. 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,(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 thatassuresensures 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 differentpart,part can put different information in the two parts. While there are legitimate use cases for this,thisit 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 ofRFC3023RFC 3023 also apply to SMIL. 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,M., St. Laurent, S., and D.Kohn E.Kohn, "XML Media Types", RFC 3023, January 2001. 8.Non-normativeInformative References [5]M.Baker, M. and P.Stark.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 Full Copyright Statement Copyright (C) The Internet Society(2006)(2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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