Network Working Group S. Kang
Request for Comments: 4179 National Computerization Agency
Category: Informational October 2005
Using Universal Content Identifier (UCI)
as Uniform Resource Names (URN)
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 (2005).
Abstract
This document describes a Uniform Resource Name (URN) namespace for
the National Computerization Agency (NCA) for naming persistent
digital resources such as music, videos, texts, images, e-books, and
other types of digital resources produced or managed by NCA.
1. Introduction
NCA is a non-profit organization with a mandate to develop and
promote information infrastructure and manage public digital contents
in Korea and possibly worldwide.
NCA has been supervising digitalization projects with various
organizations. The contents involved in such projects include
millions of technical papers, cultural properties, educational
materials, scientific research reports. Those organizations manage
the digital contents in a standardized way set by NCA and provide
users with various content services via internet.
NCA wishes to issue globally unique and persistent IDs to digital
resources and assign relevant organizations as its registration
agencies under the Universal Content Identifier (UCI) scheme. It is
beneficial for NCA, its registration agencies, and the value chain
players in e-commerce, to have the UCI URN namespace, under which all
the contents and components produced and managed by NCA are digitally
registered, identified, and resolved.
NCA has been developing and operating the UCI system that provides
registration, resolution, search, and administration functionalities.
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The functionalities are going to be added and modified once the use
of UCI URN namespace is approved. NCA would like to assign unique,
permanent, and location-independent names based on the URNs for the
resources it produces or manages. See
http://www.nca.or.kr/eindex.htm for more information on NCA.
This namespace specification is for a formal namespace.
2. Specification Template
Namespace ID:
"UCI"
Registration Information:
Registration Version Number: 1 Registration Date: 2004-07-xx
Declared registrant of the namespace:
Name : Sang-ug Kang
Affiliation: National Computerization Agency
Address : NCA Bldg. 77 Mookyo-Dong, Chung-Ku, Seoul, Korea
Phone : +82 (2) 2131-0443
Email :
Web : or
Declaration of syntactic structure:
The Namespace specific string of all URNs assigned by NCA conforms
to the syntax defined in section 2.2. of RFC2141, "URN Syntax"[1].
The syntax convention is described in the form of ABNF rules [2]
as the following.
UCI = prefix "-" instance *1(":" qualifier)
prefix = 1*(alphaDigit) *1(":" 1*(alphaDigit))
*1("+" 1*(alphaDigit))
instance = 1*(trans / "%" HEXDIG HEXDIG)
qualifier = head 1*(alphaDigit) *2("-" head 1*(alphaDigit))
trans = alphaDigit / other
alphaDigit = ALPHA / DIGIT
head = "C" / "R" / "F"
other = "(" / ")" / "+" / "," / "-" / "." / "=" / "@" /
";" / "$" / "_" / "!" / "*" / "'"
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The UCI identifier consists of two parts: prefix code and content
code. The content code is also divided into instance code and
qualifier code, which is optional. A prefix code is given to a
registration agency, subordinate registration agency, and/or its
registrants such as 'G3000+music', 'I600', 'I500+paper', and so
forth. A content code is issued to each individual digital
resource such as 'cii90007', '8987409', and so on.
Relevant ancillary documentation:
None.
Identifier uniqueness considerations:
It is the responsibility of the registration authority, or NCA, to
guarantee the uniqueness of identifiers and the names of
subordinate naming authorities. For example, a software tool
developed and used by NCA checks if a UCI identifier is being
reassigned and verifies that it is assigned to at most one
resource during the registration process.
Identifier persistence considerations:
Registration Agencies are all eligible to maintain the usability
of the UCI URNs for a reasonably long period. As a government
sponsored organization, NCA will operate a backup service and make
an effort to find a substitute in case a registration agency
becomes out of operation.
Process of identifier assignment:
Assignment of UCI identifier is delegated to the registration
agencies. NCA appoints UCI registration agencies and provides its
namespace by assigning a unique registration agency code that is a
part of NSS. Followed by the authorized namespace, each
registration agency sets its own identifier scheme that conforms
to the UCI syntactic structure.
A UCI for a digital resource is issued by the registration agency,
upon a request of a registrant. The following is an example
identifier.
e.g., urn:uci:I700-2987098
where, I700 is a registration agency code and 2987098 is an
identifier assigned to a digital content.
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Process for identifier resolution:
Resolution is controlled by NCA and its delegatees. The list of
UCI registration agency codes is maintained by the registration
authority. Each registration agency maintains the list of
subordinate registrant codes and identifiers registered to the
registration agency.
Identifier resolution steps are as follows.
- (Step1) Global resolution: NCA resolves which RA is dealing with
the associated resource by parsing the registration agency code
of the UCI.
- (Step2) Local resolution: The corresponding RA parses and
resolves the rest of the identifier
The global resolution is performed by UCI resolution server that
is open to public. (Currently http://rootadmin.uci.or.kr:9000/
{UCI identifier} will give you resolution results.)
Rules for Lexical Equivalence:
The "prefix" is case-insensitive. So there will not be two
registration agencies whose names differ only in case.
urn:uci:{prefix code}:
is case-insensitive for matches. Remainder of the identifier is
case-sensitive.
Conformance with URN Syntax:
The UCI syntax fully conforms to RFC2141 syntax rules for both NSS
and NID.
Validation mechanism:
Valid list of prefix code will be available via both on-line and
off-line upon request. The validity of the rest of identifier can
be offered via on-line service. (Currently at http://rootadmin.
uci.or.kr:9000/{UCI identifier} by typing a query UCI identifier)
Scope:
Global.
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3. Security Considerations
There are no additional security considerations beyond those normally
associated with the use and resolution of URNs in general.
4. Namespace Considerations
The Korean government has been funding the UCI project with the
vision that it will be an essential component in realizing
interoperability of digital contents owned by individual institutes
and organizations. The resolution service provided by NCA and its
registration agencies via networks will play a central role in
achieving such a goal. Moreover, the resolution service is open to
the public without discrimination.
The assignment and use of identifiers is performed according to the
rules established by NCA. It abides by the URN requirements and
syntax. Within a UCI namespace, a registration agency manages
subordinate namespaces and maintains the metadata of digital
contents.
For making the service available to the public, a global resolution
service is run by NCA through a service server and local resolution
service is provided by the corresponding registration agency.
5. Community Considerations
The assignment and use of identifiers within the namespace are open,
and the related rule is established by NCA. Registration agencies
are evaluated and selected fairly and shall have the responsibility
of processing registrants' requests for registering digital contents.
Registration authority and registration agencies shall operate
resolution servers for UCI namespace and subordinate namespaces,
respectively. Digital content users can access the resolution
servers to fetch resolution results. The reference software is
developed, and resolution servers are now in operation.
6. IANA Considerations
The IANA has registered the "UCI" namespace in the IANA registry of
URN NIDs. For more information about URN namespace, see [3].
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7. Normative References
[1] Moats, R., "URN Syntax", RFC 2141, May 1997.
[2] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[3] Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
"Uniform Resource Names (URN) Namespace Definition Mechanisms",
BCP 66, RFC 3406, October 2002.
Author's Address
Sang-ug Kang
National Computerization Agency
Bldg. 77 Mookyo-Dong,
Joong-Ku, Seoul,
Korea
Phone: 82-2-2131-0443
EMail: sukang@nca.or.kr
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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