RFC3870
Network Working Group A. Swartz Request for Comments: 3870 AaronSw.com Category: Informational September 2004
application/rdf+xml Media Type Registration
Status 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 (2004).
Abstract
This document describes a media type (application/rdf+xml) for use with the Extensible Markup Language (XML) serialization of the Resource Description Framework (RDF). RDF is a language designed to support the Semantic Web, by facilitating resource description and data exchange on the Web. RDF provides common structures that can be used for interoperable data exchange and follows the World Wide Web Consortium (W3C) design principles of interoperability, evolution, and decentralization.
Contents
Introduction
RDF is a language designed to support the Semantic Web, by facilitating resource description and data exchange on the Web. RDF provides common structures that can be used for interoperable data exchange and follows the W3C design principles of interoperability, evolution, and decentralization.
While the RDF data model [2] can be serialized in many ways, the W3C has defined the RDF/XML syntax [1] to allow RDF to be serialized in an XML format. The application/rdf+xml media type allows RDF consumers to identify RDF/XML documents so that they can be processed properly.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119 [6].
application/rdf+xml Registration
This is a media type registration as defined in RFC 2048, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures" [5].
MIME media type name: application
MIME subtype name: rdf+xml
Required parameters: none
Optional parameters: charset
Same as charset parameter of application/xml, defined in RFC
3023 [4].
Encoding considerations:
Same as charset parameter of application/xml, defined in RFC
3023 [4].
Security considerations:
See "Security Considerations" (Section 6).
Interoperability considerations:
It is RECOMMENDED that RDF documents follow the newer RDF/XML
Syntax Grammar [1] as opposed to the older RDF Model and Syntax
specification [7].
RDF is intended to allow common information to be exchanged
between disparate applications. A basis for building common
understanding is provided by a formal semantics [3], and
applications that use RDF should do so in ways that are
consistent with this.
Published specification:
see RDF/XML Syntax Grammar [1] and RDF: Concepts and Abstract
Syntax [2] and the older RDF Model and Syntax [7]
Applications which use this media type:
RDF is device-, platform-, and vendor-neutral and is supported
by a range of Web user agents and authoring tools.
Additional information:
Magic number(s): none
Although no byte sequences can be counted on to consistently
identify RDF, RDF documents will have the sequence
"http://www.w3.org/1999/02/22-rdf-syntax-ns#" to identify
the RDF namespace. This will usually be towards the top of
the document.
File extension(s): .rdf
Macintosh File Type Code(s): "rdf "
For further information:
Dan Brickley <[email protected]>
RDF Interest Group <[email protected]>
More information may be found on the RDF website:
<http://www.w3.org/RDF/>
Intended usage: COMMON
Author/Change controller:
The RDF specification is a work product of the World Wide Web
Consortium. The W3C and the W3C RDF Core Working Group have
change control over the specification.
Fragment Identifiers
The rdf:ID and rdf:about attributes can be used to define fragments in an RDF document.
Section 4.1 of the URI specification [8] notes that the semantics of a fragment identifier (part of a URI after a "#") is a property of the data resulting from a retrieval action, and that the format and interpretation of fragment identifiers is dependent on the media type of the retrieval result.
In RDF, the thing identified by a URI with fragment identifier does not necessarily bear any particular relationship to the thing identified by the URI alone. This differs from some readings of the URI specification [8], so attention is recommended when creating new RDF terms which use fragment identifiers.
More details on RDF's treatment of fragment identifiers can be found in the section "Fragment Identifiers" of the RDF Concepts document [2].
Historical Considerations
This media type was reserved in RFC 3023 [4], saying:
RDF documents identified using this MIME type are XML documents whose content describes metadata, as defined by [7]. As a format based on XML, RDF documents SHOULD use the '+xml' suffix convention in their MIME content-type identifier. However, no content type has yet been registered for RDF and so this media type should not be used until such registration has been completed.
IANA Considerations
This document calls for registration of a new MIME media type, according to the registration in Section 2.
Security Considerations
RDF is a generic format for exchanging application information, but application designers must not assume that it provides generic protection against security threats. RFC 3023 [4], section 10, discusses security concerns for generic XML, which are also applicable to RDF.
RDF data can be secured for integrity, authenticity and confidentiality using any of the mechanisms available for MIME and XML data, including XML signature, XML encryption, S/MIME, OpenPGP or transport or session level security (e.g., see [9], especially sections 3.4, 3.5, 3.10, [10], [11], [12]).
RDF is intended to be used in documents that may make assertions about anything, and to this end includes a specification of formal semantics [3]. The semantics provide a basis for combining information from a variety of sources, which may lead to RDF assertions of facts (either by direct assertion, or via logical deduction) that are false, or whose veracity is unclear. RDF application designers should not omit consideration of the reliability of processed information. The formal semantics of RDF can help to enhance reliability, since RDF assertions may be linked to a formal description of their derivation. There is ongoing exploration of mechanisms to record and handle provenance of RDF information. As far as general techniques are concerned, these are still areas of ongoing research, and application designers must be aware, as always, of "Garbage-in, Garbage-out".
Acknowledgements
Thanks to Dan Connolly for writing the first version of this document [13], to Andy Powell for <http://www.w3.org/2000/03/rdf- tracking/#mime-types-for-rdf-docs>, to Marshall Rose for his <http://xml.resource.org/> converter, and to Graham Klyne, Jan Grant, and Dave Beckett for their helpful comments on early versions of this document.
References
Normative References
[1] Beckett, D., "RDF/XML Syntax Specification (Revised)", W3C rdf-
syntax-grammar, February 2004, <http://www.w3.org/TR/2004/REC- rdf-syntax-grammar-20040210/>.
[2] Klyne, G. and J. Carroll, "Resource Description Framework (RDF):
Concepts and Abstract Syntax", W3C rdf-concepts, February 2004,
<http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/>.
[3] Hayes, P., "RDF Model Theory", W3C rdf-mt, February 2004,
<http://www.w3.org/TR/2004/REC-rdf-mt-20040210/>.
[4] Murata, M., St.Laurent, S. and D. Kohn, "XML Media Types", RFC
3023, January 2001.
[5] Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet
Mail Extensions (MIME) Part Four: Registration Procedures", BCP
13, RFC 2048, November 1996.
[6] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
Informative References
[7] Lassila, O. and R. Swick, "Resource Description Framework (RDF)
Model and Syntax Specification", W3C REC-rdf-syntax, February
1999, <http://www.w3.org/TR/REC-rdf-syntax>.
[8] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[9] Bellovin, S., Schiller, J. and C. Kaufman, Eds., "Security
Mechanisms for the Internet", RFC 3631, December 2003.
[10] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[11] Eastlake, D., Reagle, J. and D. Solo, "(Extensible Markup
Language) XML-Signature Syntax and Processing", RFC 3275, March 2002.
[12] Eastlake, D. and J. Reagle, "XML Encryption Syntax and
Processing", W3C xmlenc-core, December 2002,
<http://www.w3.org/TR/2002/REC-xmlenc-core-20021210/>
[13] Connolly, D., "A media type for Resource Description Framework
(RDF)", March 2001, <http://www.w3.org/2001/03mr/rdf_mt>.
Author's Address
Aaron Swartz AaronSw.com 349 Marshman Highland Park, IL 60035 USA
Phone: +1 847 432 8857 EMail: [email protected] URI: http://www.aaronsw.com/
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