By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as “work in progress.”
The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html.
This Internet-Draft will expire on December 14, 2007.
Copyright © The IETF Trust (2007).
This memo defines Human Readable Resource Identifiers, strings which are interpreted as IRIs, but which allow the use of characters which must be escaped in a legal IRI, such as delimiters and a few other ASCII characters.
3. Human Readable Resource Identifiers
4. Relation to IRIs
5. Security Considerations
6. IANA Considerations
7.1. Normative References
7.2. Informative References
§ Authors' Addresses
§ Intellectual Property and Copyright Statements
The syntactic constraints of IRIs (RFC 3987 (Duerst, M. and M. Suignard, “Internationalized Resource Identifiers (IRIs),” January 2005.)) and URIs (RFC 3986 (Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” January 2005.)) mandate that certain common punctuation characters (such as spaces, quotation marks, and various sorts of delimiters) must be percent encoded. However, it is often inconvenient for authors to encode these characters.
Historically, XML system identifiers and, more generally, the value of XML attributes that are intended to contain IRIs or URIs have allowed authors to provide values that use these characters literally.
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 RFC 2119 (Bradner, S., “Key words for us in RFCs to Indicate Requirement Levels,” March 1997.).
Several XML-related specifications use strings which are interpreted as IRIs, but which allow the use of characters which must be escaped in a legal IRI, such as delimiters and a few other ASCII characters. Examples include XML System Identifiers (Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and F. Yergeau, “Extensible Markup Language (XML) 1.0 (Forth Edition),” September 2006.), the href attribute in XLink (DeRose, S., Maler, E., and D. Orchard, “XML Linking Language (XLink) Version 1.0,” June 2001.), and XML Base attributes (Marsh, J., “XML Base,” June 2001.). These specifications all describe, with slightly different wording, the same algorithm for converting that string to a URI or IRI. The purpose of this RFC is to provide a single definition which can be referenced by these specifications, and to provide a name for strings of this type: Human Readable Resource Identifiers.
A Human Readable Resource Identifier (HRRI) is a sequence of Unicode characters that can be converted into an IRI by the application of a few simple encoding rules.
To convert a Human Readable Resource Identifier to an IRI reference, the following characters MUST be percent encoded:
These characters are percent encoded by applying steps 2.1 to 2.3 of Section 3.1 of RFC 3987 (Duerst, M. and M. Suignard, “Internationalized Resource Identifiers (IRIs),” January 2005.) to them.
Some strings are not Human Readable Resource Identifiers; for example, the string “%%%” is not an HRRI. A string is a legal Human Readable Resource Identifier if and only if the string generated by applying the encoding rules above is a legal IRI.
Note that in XML, the control character #x0 can never appear. Also, authors of HRRIs are advised to percent encode space characters themselves, rather than rely on the processor to do so, because spaces are often used to separate HRRIs in a sequence.
Processing a relative identifier against a base is handled straightforwardly; the algorithms of RFC 3986 (Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” January 2005.) can be applied directly, treating the characters additionally allowed in HRRIs in the same way that unreserved characters are treated in URI references.
If required, the IRI reference resulting from percent encoding an HRRI can be converted to a URI reference by following the prescriptions of Section 3.1 of RFC 3987 (Duerst, M. and M. Suignard, “Internationalized Resource Identifiers (IRIs),” January 2005.).
Conversion from a Human Readable Resource Identifier to an IRI or a URI MUST be performed only when absolutely necessary and as late as possible in a processing chain. In particular, neither the process of converting a relative Human Readable Resource identifier to an absolute one nor the process of passing a Human Readable Resource Identifier to a process or software component responsible for dereferencing it SHOULD trigger percent encoding.
Internationalized Resource Identifiers (IRIs) (Duerst, M. and M. Suignard, “Internationalized Resource Identifiers (IRIs),” January 2005.) extend URIs by allowing unescaped non-ascii characters. Human Readable Resource Identifiers go further by allowing various ASCII characters that are illegal in both URIs and IRIs. By escaping these characters Human Readable Resource Identifiers can be converted to IRIs, which can in turn be converted to URIs if required.
Human Readable Resource Identifiers have the same security considerations as IRIs, see Section 8 of  (Duerst, M. and M. Suignard, “Internationalized Resource Identifiers (IRIs),” January 2005.). In addition, the use of control characters may allow malicious users to manipulate the displayed version of an HRRI.
Human Readable Resource Identifers are often converted to IRIs or URIs and subsequently used to provide a compact set of instructions for access to network resources, care must be taken to properly interpret the data within a Human Readable Resource Identifier, to prevent that data from causing unintended access, and to avoid including data that should not be revealed in plain text.
This document has no actions for IANA.
|||Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” RFC 3986, January 2005.|
|||Bradner, S., “Key words for us in RFCs to Indicate Requirement Levels,” March 1997.|
|||Duerst, M. and M. Suignard, “Internationalized Resource Identifiers (IRIs),” RFC 3987, January 2005.|
|||Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and F. Yergeau, “Extensible Markup Language (XML) 1.0 (Forth Edition),” September 2006.|
|||DeRose, S., Maler, E., and D. Orchard, “XML Linking Language (XLink) Version 1.0,” June 2001.|
|||Marsh, J., “XML Base,” June 2001.|
|1 Network Drive|
|Building #2 MS UBUR02-201|
|Burlington, MA 01803|
|University of Edinburgh|
|HCRC, School of Informatics|
|2 Buccleuch Place|
|Edinburgh EH8 9LW|
Copyright © The IETF Trust (2007).
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.
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, THE IETF TRUST 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.
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 in BCP 78 and BCP 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 at http://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 email@example.com.
Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA).