Internet-Draft Norman Paskin
Document: draft-paskin-doi-uri-04.txt International DOI
Expires: December 2003 Foundation
Eamonn Neylon
Manifest Solutions
Tony Hammond
Elsevier
Sam Sun
CNRI
June 2003
The "doi" URI Scheme for the Digital Object Identifier (DOI)
Status of this Memo
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Abstract
This document defines the "doi" Uniform Resource Identifier (URI)
scheme for the Digital Object Identifier (DOI). DOIs are
identifiers for entities of significance to the content
industries. The "doi" URI scheme allows a resource associated with
an entity identified by a DOI to be referenced by a URI for
Internet applications. A "doi" URI is dereferenced to a set of
service descriptions through discoverable resolution mechanisms.
Table of Contents
1 Introduction..................................................2
2 Terminology...................................................3
3 The "doi" URI Scheme..........................................3
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4 Normalization and Comparison of "doi" URIs....................5
5 DOI Administration............................................6
6 DOI Resolution................................................6
7 Rationale.....................................................7
8 Security Considerations.......................................8
9 Acknowledgements..............................................8
10 References..................................................8
11 Authors' Addresses..........................................9
12 Full Copyright Statement....................................9
1 Introduction
This document defines the "doi" Uniform Resource Identifier (URI)
scheme for the Digital Object Identifier (DOI). DOIs are
identifiers for entities of significance to the content
industries. The "doi" URI scheme allows a resource associated with
an entity identified by a DOI to be referenced by a URI for
Internet applications. A "doi" URI is dereferenced to a set of
service descriptions through discoverable resolution mechanisms.
The term "Digital Object Identifier" should be construed as
meaning an identifier ("Identifier") of an entity ("Object") for
use in networked environments ("Digital"). In this sense an
"Object" can be any entity - any digital or physical manifestation
or performance, or any abstract work or concept - that is
identified by a DOI.
Some concepts relevant to DOI follow:
International DOI Foundation (IDF) û The International DOI
Foundation, Inc. is a non-stock membership corporation
organized in 1997 and existing under and by virtue of the
General Corporation Law of the State of Delaware, USA. The
Foundation is controlled by a Board elected by the members of
the Foundation. The Corporation is a "not-for-profit"
organization, i.e. prohibited from activities not permitted to
be carried on by a corporation exempt from US federal income
tax under Section 501(c)(6) of the Internal Revenue Code of
1986 et seq.
The activities of the Foundation are controlled by its members,
operating under a legal Charter and formal By-laws. Membership
is open to all organizations with an interest in electronic
publishing, content distribution, rights management, and
related enabling technologies.
The Foundation was founded to develop a framework of
infrastructure, policies and procedures to support the
identification needs of the content industries.
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DOI Prefix Holder û Any network user who has been assigned the use
of a DOI naming authority under which DOIs may be created.
DOI Registration Agency - An IDF-appointed body that provides
administration facilities to DOI Prefix Holders.
DOI Resolution û A process of service indirection whereby a
service is selected from a set of service descriptions returned
on dereference of a "doi" URI and this service subsequently
activated.
DOI Service û One or more network services accessible on
resolution of a DOI.
DOI Metadata û A set of data associated with a DOI which is
deposited into a repository at time of creation by a DOI
Registration Agency and thereafter maintained.
2 Terminology
In this document the key words "must", "must not", "required",
"shall", "shall not", "should", "should not", "recommended",
"may", and "optional" are to be interpreted as described in RFC
2119 [1] and indicate requirement levels for compliant
implementations.
3 The "doi" URI Scheme
3.1 Definition of "doi" URI Syntax
The "doi" URI syntax defined in this document conforms to the
generic URI syntax. This specification uses the Augmented Backus-
Naur Form (ABNF) notation of RFC 2234 [2] to define the URI. The
following core ABNF productions are used by this specification as
defined by Section 6.1 of RFC 2234: ALPHA, DIGIT, HEXDIG. The
complete "doi" URI syntax is as follows:
doi-uri = scheme ":" encoded-doi [ "?" query ]
[ "#" fragment ]
scheme = "doi"
encoded-doi = prefix "/" suffix
prefix = segment
suffix = segment *( "/" segment )
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segment = *pchar
query = *( pchar / "/" / "?" )
fragment = *( pchar / "/" / "?" )
pchar = unreserved / escaped / ";" /
":" / "@" / "&" / "=" / "+" / "$" / ","
unreserved = ALPHA / DIGIT / mark
escaped = "%" HEXDIG HEXDIG
mark = "-" / "_" / "." / "!" / "~" / "*" / "'" /
"(" / ")"
A "doi" URI has an (encoded) DOI as its scheme-specific part
followed by an optional query component followed by an optional
fragment identifier. A DOI is constructed by appending a unique
suffix string to an assigned prefix string separated by a slash
"/" character. The prefix is always assigned to a DOI Prefix
Holder by a DOI Registration Agency. The DOI Prefix Holder is
responsible for the creation of a valid suffix. The prefix in a
DOI corresponds to the naming authority. The administration of any
particular DOI may be transferred to another party at any time.
The prefix does not denote the owner of a DOI.
ANSI/NISO Z39.84-2000 [3] is the authoritative reference that
specifies the rules for constructing a DOI. Once constructed, a
DOI may be regarded as an opaque identifier with no internal
structure. The minimum constraints for validation of a DOI string
are that the prefix and suffix components be non-empty.
3.2 Allowed Characters Under the "doi" URI Scheme
The syntax for a DOI is defined in accordance with the ANSI/NISO
Z39.84-2000 standard "Syntax for the Digital Object Identifier
Syntax". A DOI is represented using the Unicode [4] character set
and is encoded in UTF-8 [5].
The "doi" URI syntax uses the same set of allowed US-ASCII
characters as specified in RFC 2396 [6] for a generic URI.
Reserved characters as well as excluded US-ASCII characters and
non-US-ASCII characters must be escaped before forming the URI.
Details of the escape encoding can be found in RFC 2396, section
2.4.
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3.3 Examples of "doi" URIs
Some examples of syntactically valid "doi" URIs are given below:
(a) doi:alpha-beta/182.342-24
where "alpha-beta" is the prefix and "182.342-24" is the suffix.
(b) doi:10.abc/ab-cd-ef
where "10.abc" is the prefix and "ab-cd-ef" is the suffix.
(c) <rdf:Description about="doi:10.23/2002/january/21/4690"/>
where "10.23" is the prefix and "2002/january/21/4690" is the
suffix.
(d) doi:11.a.7/0363-0277(19950315)120%3A5%3C%3E1.0.TX%3B2-V
where "11.a.7" is the prefix and "0363-
0277(19950315)120%3A5%3C%3E1.0.TX%3B2-V" is the prefix. Note that
in unescaped form this DOI is represented in UTF-8 as
"11.a.7/0363-0277(19950315)120:5<>1.0.TX;2-V".
(e) doi:dk/P%C3%A6dagogi%2037(2),%20562
where "dk" is the prefix and "P%C3%A6dagogi%2037(2),%20562" is the
suffix. Note that in unescaped form this DOI is represented in
UTF-8 as "dk/P¾dagogi 37(2), 562" and in ISO-Latin-1 as
"dk/Pdagogi 37(2), 562".
4 Normalization and Comparison of "doi" URIs
In order to facilitate comparison of "doi" URIs and to reduce the
risk of false negatives, normalization to the canonical form
should be applied to minimize the amount of software processing
for such comparisons.
The following normalization steps should be applied:
1. Normalize the case of the leading "doi:" token to be
lowercase
2. Unescape all unreserved %-escaped characters
3. Normalize the case of the scheme-specific part
including any %-escaped characters to be uppercase
The following forms of a "doi" URI
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1. DOI:dk/P%C3%A6dagogi%2037(2),%20562
2. doi:DK/P%C3%A6dagogi%2037(2),%20562
3. doi:dk/P%c3%a6dagogi%2037(2),%20562
4. doi:dk/p%c3%a6dagogi%2037(2),%20562
5. doi:dk%2FP%C3%A6dagogi%2037%282%29%2C%20562
are normalized to the canonical form
doi:DK/P%C3%A6DAGOGI%2037(2),%20562
5 DOI Administration
The International DOI Foundation (IDF) is a not-for-profit
membership-based organization founded to develop a framework of
infrastructure, policies and procedures to support the
identification needs of the content industries.
The IDF is the maintenance agency for DOI and appoints DOI
Registration Agencies.
DOIs are created by DOI Prefix Holders and must be registered via
a DOI Registration Agency. Any network user can become a DOI
Prefix Holder by agreement with a DOI Registration Agency.
DOI Registration Agencies perform the following functions:
allocating DOI prefixes, registering DOIs, and providing the
necessary infrastructure to allow DOI Prefix Holders to declare
and maintain the metadata associated with a particular DOI. DOI
Registration Agencies also maintain knowledge of the current owner
of each individual DOI to ensure administrative updates.
The IDF maintains the DOI system (to allow registration and ensure
resolution of DOIs) and provides governance to ensure appropriate
use. DOI assignment requires a fee to ensure that the system costs
are met. This allows the system to be managed and supports
persistence as a function of organization rather than technology.
The fee is for the registering of DOIs (and may optionally be
passed on to registrants, waived or subsidized by a DOI
Registration Agency), but not for the resolution of a DOI.
The DOI system relies on copyright and trademark law to protect
the DOI brand and reputation. DOI is not a patented system; the
IDF has not developed any patent claims on the DOI system and does
not rely on patent law for remedy.
6 DOI Resolution
A "doi" URI references a set of service descriptions which is
returned on dereference of the URI. Following such a dereference a
service description is typically selected and the corresponding
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service activated. This process of service indirection is commonly
referred to as "resolution" a DOI. Examples of services that can
be accessed by the resolution of a DOI include redirection to
another network resource, return of a metadata record describing
the entity identified by the DOI, etc. A discussion of such
services is beyond the scope of this document.
Resolution of a DOI can be accomplished using a variety of network
protocols. The combination of a network protocol, an access method
defined by that protocol and a service endpoint provides the means
of access to a resolution mechanism. As the maintenance agency for
DOI, the IDF will publish the means of access for known resolution
mechanisms of DOI. For the use of other resolution mechanisms
prior knowledge of the means of access is required.
As such a "doi" URI can be classified both as a name and a
locator. The locator references a set of service descriptions.
Note that this locator must not be confused with the locator used
to retrieve the ultimate representation that may be returned as a
result of activating a service. The "doi" URI is thus an instance
of an application-level URI and requires a methodology for mapping
from the "doi" URI to a proxy locator URI in order to realize its
locator role. These mapping methodologies provide the resolution
mechanisms that enable a "doi" URI to function as a locator of a
set of services.
7 Rationale
7.1 Why Create a New URI Scheme for DOI?
Under RFC 2718, "Guidelines for new URL Schemes" [7], it is stated
that a URI scheme should have a "demonstrated utility", and in
particular should be applied to "things that cannot be referred to
in any other way". DOI meets both of these criteria in that it is
a well established identifier (see <http://www.doi.org/>) for
entities of significance to the content industries, with some 10
million examples in current use on the Internet, and is being
widely embraced by the content industries. DOI is not bound to any
Internet protocol and so requires its own dedicated URI scheme.
The administration granularity of existing URI schemes typically
operates at the authority component level. By contrast DOIs are
managed at the individual identifier level. It is for this reason
that the DOI prefix is not to be interpreted as an "owner"
authority but rather as the "creator" authority. Once created the
"doi" URI may be regarded as an opaque identifier with no internal
structure.
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7.2 Why Not Use a URN Namespace ID for DOI?
RFC 2396 states that a "URN differs from a URL in that it's [sic]
primary purpose is persistent labeling of a resource with an
identifier". A "doi" URI on the other hand has a dual purpose:
both to allow a resource associated with an entity identified by a
DOI to be referenced by a URI for Internet applications, as well
as to enable access to a set of service descriptions. In this
regard a "doi" URI scheme should be considered as being similar to
the "tel", "fax" and "modem" URI schemes documented in RFC 2806
[8].
Further the syntactic requirements of the "doi" URI scheme are
incompatible with the URN syntax. Specifically the use of optional
query component and/or fragment identifier cannot be accommodated
by the URN syntax (cf. Sect. 2.3.2, RFC 2141 [9]).
8 Security Considerations
The "doi" URI scheme is subject to the same security
considerations as the general URI scheme described in RFC 2396.
Dereference of a "doi" URI to access a set of service descriptions
will be subject to the security considerations of the underlying
protocol used to access the resource referenced by the "doi" URI.
9 Acknowledgements
The authors acknowledge the contributions of Larry Lannom and
Jason Petrone, of the Corporation for National Research
Initiatives, to this specification.
The authors are also grateful to Larry Masinter and Martin Duerst
for their constructive comments on this specification.
10 References
1. Bradner, S., "Key Words for Use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
2. Crocker, D.H. and Overell, P., "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
3. ANSI/NISO Z39.84-2000, "Syntax for the Digital Object
Identifier", ISBN 1-880124-47-5.
4. The Unicode Consortium, "The Unicode Standard", Version 3, ISBN
0-201-61633-5, as updated from time to time by the publication of
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new versions. (See
http://www.unicode.org/unicode/standard/versions for the latest
version and additional information on versions of the standard and
of the Unicode Character Database).
5. Yergeau, F., "UTF-8, A Transformation Format for Unicode and
ISO10646", RFC 2279, October 1996.
6. Berners-Lee, T., R. Fielding and L. Manister, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
7. Masinter, L., H. Alvestrand, D. Zigmond and P. Petke,
"Guidelines for new URL Schemes", RFC 2718, November 1999.
8. Vaha-Sipila, A., "URLs for Telephone Calls", RFC 2806, April
2000.
9. Moats, R., "URN Syntax", RFC 2141, May 1997.
11 Authors' Addresses
Norman Paskin
The International DOI Foundation
Linacre House, Jordan Hill
Oxford, OX2 8DP, UK
n.paskin@doi.org
Eamonn Neylon
Manifest Solutions
Bicester
Oxfordfordshire, OX26 2HX, UK
eneylon@manifestsolutions.com
Tony Hammond
Elsevier Ltd
32 Jamestown Road
London, NW1 7BY, UK
t.hammond@elsevier.com
Sam Sun
Corporation for National Research Initiatives
1805 Preston White Dr., Suite 100
Reston, VA 20191, USA
ssun@cnri.reston.va.us
12 Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
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