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 This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. 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 Paskin Expires - November 2003 [Page 1] The "doi" URI Scheme May 2003 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. Paskin Expires - November 2003 [Page 2] The "doi" URI Scheme May 2003 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" | Paskin Expires - November 2003 [Page 3] The "doi" URI Scheme May 2003 "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. Paskin Expires - November 2003 [Page 4] The "doi" URI Scheme May 2003 (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 Paskin Expires - November 2003 [Page 5] The "doi" URI Scheme May 2003 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? Paskin Expires - November 2003 [Page 6] The "doi" URI Scheme May 2003 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. Paskin Expires - November 2003 [Page 7] The "doi" URI Scheme May 2003 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, Paskin Expires - November 2003 [Page 8] The "doi" URI Scheme May 2003 published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. 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