Network Working GroupD. Orchard
Internet-DraftAyogo Games, Inc.
Intended status: InformationalR. Salz
Expires: April 2011IBM
J. Reschke, Editor
October 2010

The QName URN Namespace


This specification defines a Uniform Resource Name namespace for XML namespace-qualified names, QNames. As long as the URN is encoded in the same character set as the document containing the original QName, the Qname URN provides enough information to maintain the semantics, and optionally the exact syntax, of the original name.

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Editorial Note (To be removed by RFC Editor before publication)

Please send comments to the xml-dev mailing list (<>).

XML versions, latest edits and the issues list for this document are available from <>.

 I  edit   (type: edit, status: open)
julian.reschke@greenbytes.de2010-03-07 Umbrella issue for editorial changes.
 I  curie   (type: edit, status: open)
julian.reschke@greenbytes.de2009-12-12 Maybe we should clarify the relation with CURIEs (which can be confused with QNames)?
 I  qname-vs-expname   (type: edit, status: open)
julian.reschke@greenbytes.de2009-12-12 There's a risk that we confuse people by claiming this is about QNames. What we map to URNs is the triple (namespace-name, local-name, prefix), where the prefix is optional. The tuple (namespace-name, local-name) is the *expanded name*, not the QName. Options: (1) just clarify the prose, (2) rename the URN scheme (is it in use already?) to something like "xmlname".
 I  i18n   (type: change, status: open)
julian.reschke@greenbytes.de2009-12-11 Need to state how non-ASCII characters are mapped to the URN.

1. Introduction and Motivation

This specification defines a Uniform Resource Name namespace for XML namespace-qualified names, QNames. As long as the URN is encoded in the same character set as the document containing the original QName, the Qname URN provides enough information to maintain the semantics, and optionally the exact syntax, of the original name.

There are a variety of situations when a QName may need to be mapped to a URI. For example, when exchanging (or referencing) an identifier for an XML element contained within a document, and the medium of exchange prefers URIs to QNames, such as an XML Schema anyURI data type. Another scenario is for comparing the identifiers, which can be simpler by comparing just a string without having to also compare the context setting XML namespace attribute that may be declared arbitrarily earlier in the document.

The XML Namespaces specification [XMLNS] does not provide a canonical mapping between QNames and URIs. Any XML specification that wants to enable identifier exchanges must define a language specific QName to URI mapping. There have emerged a variety of different algorithms and solutions for the mapping. To date, there have been no standardized algorithms available that they can re-use, which has increased their efforts. A standardized mapping, such as this, should provide increased productivity.

Almost all of the algorithms for Qname to URI mappings are based upon concatenation of the URI and the name with variations based upon prefix inclusion, namespace name and name separator, etc. These are typically problematic because it is difficult to recover the QName from the URI as the namespace name and name separator may have already been used in the namespace name. Having the namespace name at the end of the identifier string avoids these and other problems.

2. Namespace Registration Template

The following paragraphs contain the URN namespace registration data, as defined in [RFC3406].

Namespace ID:

 I  reg-info   (type: edit, status: open)
julian.reschke@greenbytes.de2009-12-11 Update registration info.

Registration Information:

Declared registrant of the namespace:

Declaration of syntactic structure:

Relevant ancillary documentation:

Identifier uniqueness considerations:

Identifier persistence considerations:

Process of identifier assignment:

Process for identifier resolution:

Rules for Lexical Equivalence:

Conformance with URN Syntax:

Validation mechanism:


3. Security Considerations

QName URN's provide a way to transcribe XML QName's into and out of URN syntax. Any security considerations are inherited from the original QName.

4. Normative References

Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and F. Yergeau, “Extensible Markup Language (XML) 1.0 (Fifth Edition)”, W3C REC-xml-20081126, November 2008, <>.
Bray, T., Hollander, D., Layman, A., Tobin, R., and H. Henry, “Namespaces in XML 1.0 (Third Edition)”, W3C REC-xml-names-20091208, December 2009, <>.
Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom, “Uniform Resource Names (URN) Namespace Definition Mechanisms”, BCP 33, RFC 3406, October 2002.
Crocker, D., Ed. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF”, STD 68, RFC 5234, January 2008.

Appendix A. Change Log (to be removed by RFC Editor before publication)

A.1. Since draft-rsalz-qname-urn-00

Updated references and fix reference to XMLNS which was meant to reference XMLNS11. Add a set of issues: "any-uri", "contacts", "curie", "examples", "i18n", "mailing-list", "qname-vs-expname", "reg-info", "registrant", "xml11".

A.2. Since draft-rsalz-qname-urn-01

Close issues "contacts" and "mailing-list" as resolved (already in -01). Close issues "registrant" and "xml11". Update registration info ("reg-info").

Authors' Addresses

David Orchard
Ayogo Games, Inc.
Rich Salz
Julian F. Reschke (editor)
greenbytes GmbH
Hafenweg 16
Muenster, NW 48155