Network Working Group                                          A. Swartz
Not-Yet-Internet-Draft                                      Info Network
Category: Informational                                       April 2001

Media Type for Resource Description Framework (RDF)

Status of this Memo

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This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.

Abstract

This memorandum describes a media type (application/rdf+xml) for use with the XML serialization of the Resource Description Framework (RDF). RDF is currently used for semantically-meaningful data on the World Wide Web, and is meant to help bring about the creation of a "Semantic Web" with semantically-meaningful information which machines are better able to process.

Introduction

The World Wide Web Consortium has issued Resource Description Framework (RDF) Model and Syntax Specification [XRDF]. To enable the exchange of RDF network entities, serialized using XML [XML], this document registers the application/rdf+xml media type.

Resource Description Framework (RDF) is a foundation for transmitting and processing semantically-meaningful data on the World Wide Web. It emphasizes facilities to enable automated processing of Web resources.

While the RDF model can be serialized in a number of different ways, the media type registered by this document only deals with the XML serialization. Future registrations are expected to deal with alternate serializations.

Because RDF is a format for semantically-meaningful information, it is important to note that transmission of RDF under this media type, whether via HTTP, SMTP or some similar protocol, means that the sender asserts the content of the RDF document. If this is not desirable, such as when a system is forwarding RDF written by someone else, another applicable media type, such as application/xml or application/octet-stream should be used. Also note that RDF provides reification so that RDF statements can be sent and discussed without actually being asserted themselves.

Registration Information

The following is a registration for the RDF media type in accordance with [MREG].

Media type name:

application

Media subtype name:

rdf+xml

Required parameters:

none

Optional parameters:

charset

Same as charset parameter of application/xml as specified in RFC 3023.

Encoding considerations:

Same as encoding considereations of application/xml as specified in RFC 3023.

Security considerations:

Security considerations include many of those described in section 10 of [XMLT] and more, due to the semantic nature of RDF. RDF documents may make assertions about anything, and thus RDF-based systems must be certain that they can trust the document. It is expected that future work with Digital Signature and "Web of Trust" will make it more clear how to build secure RDF systems.

Interoperability considerations:

For maximum interoperability it is recommend that RDF files use the Basic RDF Syntax, since this is most likely to be understood by RDF parsers and remain stable through future RDF specifications. It is also recommended that RDF documents do not use processing instructions, as RDF parsers give no meaning to them.

Published specification:

Resource Description Framework (RDF) Model and Syntax Specification [XRDF]

Applications which use this media type:

RDF is device-, platform-, and vendor-neutral and is supported by a wide range of Web user agents and authoring tools.

Additional information:

Magic number:: 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:: The file extensions ".rdf" and ".xrdf" are commonly used.
Macintosh File Type code:: "TEXT" or "XRDF"
Person & email address to contact for further information:: Dan Connolly <connolly@w3.org> (anybody want their name in lights in my stead?)
Aaron Swartz <me@aaronsw.com>
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

Section 4.1 of the URI specification [URI] 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.

While as of publication, no media type for RDF had been defined yet, it is expected that the rdf:ID attribute will be used to define fragment identifiers.

Historical Considerations

This media type was reserved in [XMLMT]:

8.18 Application/rdf+xml

Content-type: application/rdf+xml

<?xml version="1.0" ?>

RDF documents identified using this MIME type are XML documents whose content describes metadata, as defined by [RDF]. 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.

References

[MREG]: Freed, N., Hlensin, J., and J. Postel, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", RFC 2048, Novemeber 1996.
[URI]: Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[XML]: Bray, T., Paoli, J., Sperberg-McQueen, C. M., and E. Maler, "Extensible Markup Language (XML) 1.0 (Second Edition)", <http://www.w3.org/TR/2000/REC-xml-20001006>, October 2000.
[XMLMT]: Murata, M., St.Laurent, S., and D. Kohn, "XML Media Types", RFC 3023, January 2001.
[XRDF]: Lassila, O. and R. Swick, "Resource Description Framework (RDF) Model and Syntax Specification", <http://www.w3.org/TR/1999/REC-rdf-syntax-19990222>, February 1999.

Author's Address

Aaron Swartz
Info Network
349 Marshman
Highland Park, IL 60035
USA
mailto:me@aaronsw.com
http://www.aaronsw.com/

Daniel W. Connolly
World Wide Web Consortum (W3C)
MIT Laboratory for Computer Science
545 Technology Square
Cambridge, MA 02139
USA
mailto:connolly@w3.org
http://www.w3.org/People/Connolly/

Acknowledgements/@@Fodder

These are from Dan Connolly, who wrote the first version of this draft.

Andy Powell, for raising the issue.

Jim Davis for his HTML->internet-draft tool (Makefile)

Larry Masinter for help with process gunk on our last RFC.

Ron Daniel for his message pointing me at section 8.18 of RFC3023 (again?).

ietf-xml-mime mailing list

oops... I thought RDF would fit under mode/*, but after readingRFC2077, I see model/* is about physica/spacial models only, not about abstract models in general. Is there a UML media type registered yet?