Internet-Draft Norman Paskin
Document: draft-paskin-doi-uri-03.txt IDF
Expires: November 2003 Eamonn Neylon
Manifest Solutions
Tony Hammond
Elsevier
Sam Sun
CNRI
May 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 intellectual
property communities. The "doi" URI scheme allows a resource for
an entity identified by a DOI to be referenced by a URI for
Internet applications. A "doi" URI is dereferenced to a set of
network services through an appropriate resolution system. The
binding between the "doi" URI and the resource which it references
is managed and is persistent over time.
Table of Contents
1 Introduction..................................................2
2 Terminology...................................................3
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3 The "doi" URI Scheme..........................................3
4 Lexical Equivalence for the "doi" URI Scheme..................5
5 Examples of Lexical Equivalence for the "doi" URI Scheme......5
6 DOI Administration............................................5
7 DOI Resolution................................................6
8 Rationale.....................................................6
9 Security Considerations.......................................7
10 Acknowledgements............................................7
11 References..................................................7
12 Authors' Addresses..........................................8
13 Full Copyright Statement....................................8
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 intellectual
property communities. The "doi" URI scheme allows a resource for
an entity identified by a DOI to be referenced by a URI for
Internet applications. A "doi" URI is dereferenced to a set of
network services through an appropriate resolution system. The
binding between the "doi" URI and the resource which it references
is managed and is persistent over time.
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 - that is identified by a
DOI.
Some concepts relevant to DOI follow:
International DOI Foundation (IDF) û A not-for-profit membership-
based organization founded to develop a framework of
infrastructure, policies and procedures to support the
identification needs of the intellectual property communities.
DOI Registration Agency - An IDF-appointed body that provides
administration facilities to DOI Prefix Holders.
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 Service û One or more network services accessible on
dereference of a DOI.
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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
RFC2119 [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 as specified in RFC 2396 [2] and follows the
"opaque_part" production rule. The complete BNF for a "doi" URI
using the grammar of RFC 822 [3] as amended by RFC 2396, section
1.6, is as follows:
doi_uri = scheme ":" doi_identifier
scheme = "doi"
doi_identifier = prefix "/" suffix
prefix = *uric_no_slash
suffix = *uric
where the following productions are taken directly from RFC 2396:
uric_no_slash = unreserved | escaped | ";" | "?" | ":" | "@" |
"&" | "=" | "+" | "$" | ","
uric = reserved | unreserved | escaped
reserved = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" |
"$" | ","
unreserved = alphanum | mark
mark = "-" | "_" | "." | "!" | "~" | "*" | "'" |
"(" | ")"
escaped = "%" hex hex
hex = digit | "A" | "B" | "C" | "D" | "E" | "F" |
"a" | "b" | "c" | "d" | "e" | "f"
alphanum = alpha | digit
alpha = lowalpha | upalpha
lowalpha = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" | "i" |
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"j" | "k" | "l" | "m" | "n" | "o" | "p" | "q" | "r" |
"s" | "t" | "u" | "v" | "w" | "x" | "y" | "z"
upalpha = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" |
"J" | "K" | "L" | "M" | "N" | "O" | "P" | "Q" | "R" |
"S" | "T" | "U" | "V" | "W" | "X" | "Y" | "Z"
digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" |
"8" | "9"
A "doi" URI has a DOI as its scheme-specific part. 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 [4] is the authoritative reference that
specifies the rules for constructing a DOI. Once constructed, a
DOI should 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 [5] character set
and is encoded in UTF-8 [6].
The "doi" URI syntax uses the same set of allowed US-ASCII
characters as specified in RFC 2396 for a generic URI. No special
characters are reserved, although certain US-ASCII characters are
excluded from all URIs.
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.
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.
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(b) doi:10.abc/ab-cd-ef
where "10.abc" is the prefix and "ab-cd-ef" is the suffix.
(c)
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".
4 Lexical Equivalence for the "doi" URI Scheme
The DOI is a case-insensitive identifier. As it is often desirable
to determine if two "doi" URIs are the same without resolving them
a general purpose means of doing so is by testing for "lexical
equivalence" as defined below.
Two "doi" URIs are lexically equivalent if they are octet-by-octet
equal after the following preprocessing:
1. Normalize the case of the leading "doi:" token to be
lowercase
2. Normalize the case of the scheme-specific part
including any %-escaped characters to be lowercase
Note that %-escaped characters must not be removed.
5 Examples of Lexical Equivalence for the "doi" URI Scheme
The following comparisons highlight the lexical equivalence
definitions for "doi" URIs:
1. doi:10.abc/ab-cd-ef
2. doi:10.ABC/ab-cd-ef
3. doi:10.ABC/AB-cd-ef
4. doi:10.ABC/AB-CD-ef
5. doi:10.ABC/AB-CD-EF
All the above "doi" URIs are lexically equivalent.
6 DOI Administration
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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 intellectual property communities.
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.
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 legal administrative updates.
7 DOI Resolution
A "doi" URI is dereferenced to one or more network services. This
dereference process is known as "resolution" of the DOI. Examples
of network services that can be accessed on resolution of the DOI
include redirection to another network resource, return of a
metadata record describing the entity identifed by the DOI, etc.
Resolution of a DOI is accomplished through an appropriate
resolution service using a network protocol specific to that
service.
8 Rationale
8.1 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 ) for
entities of significance to the intellectual property communities,
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 an Internet protocol and so requires its own dedicated
URI scheme.
8.2 Why Not Use an Existing URI Scheme for DOI?
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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 should be regarded as an opaque identifier with no internal
structure. For this reason a "doi" URI has no relative URI forms.
8.3 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 on the other hand has a dual purpose: both to
provide for the persistent identification of an entity of
significance to the intellectual property communities, as well as
to enable access to a set of network services. 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].
9 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 network services will be
subject to the security considerations of the underlying protocol
used to access the resource referenced by the "doi" URI.
10 Acknowledgements
The authors gratefully acknowledge the contributions of Larry
Lannom and Jason Petrone, of the Corporation for National Research
Initiatives, to this specification.
11 References
1. Bradner, S., "Key Words for Use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
2. Berners-Lee, T., R. Fielding and L. Manister, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
3. Crocker, D., "Standard for the Format of ARPA Internet Text
Messages", STD 11, RFC 822, August 1982.
4. ANSI/NISO Z39.84-2000, "Syntax for the Digital Object
Identifier", ISBN 1-880124-47-5.
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5. The Unicode Consortium, "The Unicode Standard", Version 3, ISBN
0-201-61633-5, as updated from time to time by the publication of
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).
6. Yergeau, F., "UTF-8, A Transformation Format for Unicode and
ISO10646", RFC 2279, October 1996.
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.
12 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
13 Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished
to others, and derivative works that comment on or otherwise
explain it or assist in its implementation may be prepared, copied,
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