Network Working Group P. Stickler Internet-Draft Nokia Research Center Expires: July 17, 2002 January 16, 2002 The 'hrn:' URI Scheme for Hierarchical Resource Names draft-pstickler-hrn-00 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. This Internet-Draft will expire on July 17, 2002. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract This document describes the 'hrn:' Uniform Resource Identifier (URI) scheme for hierarchical resource names. The 'hrn:' URI scheme belongs to the class of Hierarchical URI Schemes as defined in RFC 2396 "Uniform Resource Identifiers (URI): Generic Syntax". This URI scheme is also a type of URN, as defined by RFC 2396, but is not a namespace of the 'urn:' URI scheme. Stickler Expires July 17, 2002 [Page 1] Internet-Draft The hrn: URI Scheme January 2002 Table of Contents 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. BNF for the 'hrn:' URI Scheme . . . . . . . . . . . . . . . . . 3 3. Hierarchical Characteristics of 'hrn:' URIs . . . . . . . . . . 4 4. Support for Autogenerated, Non-Mnemonic Names . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 Full Copyright Statement . . . . . . . . . . . . . . . . . . . . 8 Stickler Expires July 17, 2002 [Page 2] Internet-Draft The hrn: URI Scheme January 2002 1. Overview The 'hrn:' URI scheme is intended for defining resource names (URNs) which may be hierarchically organized, such that resources may be logically related by their URI structure. The 'hrn:' URI scheme belongs to the class of Hierarchical URI Schemes as defined in RFC 2396 "Uniform Resource Identifiers (URI): Generic Syntax" [4] and as such provides for parsing into distinct subcomponents, each constituting a hierarchically distinct level. The hierarchical characteristics of 'hrn:' URIs are discussed later in this document. This URI scheme is also a type of URN, as defined by RFC 2396, but is not a namespace of the 'urn:' URI scheme [5], because the 'urn:' scheme does not provide for hierarchical characteristics which are central to the semantics of this URI scheme. Examples: hrn://abc.com/288918293/3/en/global/docbook hrn://abc.com/288918293/3/sp/europe/xhtml hrn://-/f81d4fae-7dec-11d0-a765-00a0c91e6bf6 hrn://-/f81d4fae-7dec-11d0-a765-00a0c91e6bf6/xml hrn://-/f81d4fae-7dec-11d0-a765-00a0c91e6bf6/pdf hrn://-/f81d4fae-7dec-11d0-a765-00a0c91e6bf6/html hrn://john.doe@widgets.org/thesis These examples are provided for illustrative purposes only and do not necessarily constitute actual URIs. See the BNF definition below for an explicit definition of 'hrn:' URI syntax. 2. BNF for the 'hrn:' URI Scheme This is a BNF-like description of the 'hrn:' Uniform Resource Identifier syntax, using the conventions of RFC 822[1], except that "|" is used to designate alternatives, and brackets [] are used around optional or repeated elements. Briefly, literals are quoted with "", optional elements are enclosed in [brackets], and elements may be preceded with * to designate n or more repetitions of the following element; n defaults to 0. This BNF description adopts sub-definitions defined in RFC 1738 "Uniform Resource Locators (URL)" [2]. The definition of UUID is adopted from the Internet Draft draft-kindel-uuid-uri-00 [3] defining the UUID string representation conforming to ISO-11578 [7] and adopted by RFC 2518 "HTTP Extensions for Distributed Authoring -- WEBDAV" [6]. Stickler Expires July 17, 2002 [Page 3] Internet-Draft The hrn: URI Scheme January 2002 hrn-URI = "hrn://" authority [ "/" name-path ] hrn-URI = "hrn://-/" UUID [ "/" name-path ] authority = [ user "@" ] host name-path = name *( "/" name ) name = 1*uchar ; Sub-definitions adopted from draft-kindel-uuid-uri-00: UUID = 8hex "-" 4hex "-" 4hex "-" 4hex "-" 12hex ; Sub-definitions adopted from RFC 1738: host = hostname | hostnumber hostname = *[ domainlabel "." ] toplabel domainlabel = alphadigit | alphadigit *[ alphadigit | "-" ] alphadigit toplabel = alpha | alpha *[ alphadigit | "-" ] alphadigit hostnumber = digits "." digits "." digits "." digits user = *[ uchar | ";" | "?" | "&" | "=" ] lowalpha = "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" hialpha = "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" alpha = lowalpha | hialpha digits = 1*digit alphadigit = alpha | digit safe = "$" | "-" | "_" | "." | "+" extra = "!" | "*" | "'" | "(" | ")" | "," hex = digit | "A" | "B" | "C" | "D" | "E" | "F" | "a" | "b" | "c" | "d" | "e" | "f" escape = "%" hex hex unreserved = alpha | digit | safe | extra uchar = unreserved | escape 3. Hierarchical Characteristics of 'hrn:' URIs The 'hrn:' URI scheme belongs to the class of Hierarchical URI Schemes as defined in RFC 2396 "Uniform Resource Identifiers (URI): Generic Syntax" [4] and as such provides for parsing into distinct Stickler Expires July 17, 2002 [Page 4] Internet-Draft The hrn: URI Scheme January 2002 subcomponents, each constituting a hierarchically distinct level. Each 'hrn:' URI containing one or more levels beyond the URI authority implies an 'hrn:' URI for each level up to and including the authority level, though implied 'hrn:' URIs need not have any properties associated with them nor be meaningful to any particular system. Note that it is not required that an 'hrn:' URI encoded name have any levels beyond the first name level. Thus, the 'hrn:' URI scheme is suitable both for simple, "flat" names as well as for hierarchical names. E.g. the following 'hrn:' URI hrn://abc.com/288918293/3/en/global/docbook implies all of the following superordinate 'hrn:' URIs hrn://abc.com/288918293/3/en/global hrn://abc.com/288918293/3/en hrn://abc.com/288918293/3 hrn://abc.com/288918293 hrn://abc.com No special meaning or interpretation is ascribed by this specification to particular 'hrn:' URI levels or to the relations between 'hrn:' URI levels other than the following: o the first level of an 'hrn:' URI corresponds to the authority defining the name hierarchy (which may be implicit in a UUID root name as indicated by a hyphen '-') o the second level of an 'hrn:' URI corresponds to the manditory root name o each of the levels beyond the second level corresponds to a sub-name o the resource denoted by the 'hrn:' URI for a sub-name level is subordinate in some manner to all resources denoted by each name level 'hrn:' URI implied by its hierarchical structure A given application may choose to conduct queries based on implied superordinate 'hrn:' URIs to retrieve any properties of any superordinate resources which may be relevant to the interpretation of a given 'hrn:' URI. Stickler Expires July 17, 2002 [Page 5] Internet-Draft The hrn: URI Scheme January 2002 Other, more specialized, URI schemes which are derived from the 'hrn:' URI scheme may ascribe more specific interpretations to particular levels implicit in the URI as well as more specific relational semantics between different levels. Note that the URI scheme prefix "hrn:" is considered to be a valid URI denoting this URI scheme, though it is not itself a valid URI according to this URI scheme. 4. Support for Autogenerated, Non-Mnemonic Names The UUID form of an 'hrn:' URI is intended for cases where a either an autogenerated or non-mnemonnic resource name is needed or desireable. 5. Security Considerations This document raises no known security issues. References [1] Crocker, D., "STANDARD FOR THE FORMAT OF ARPA INTERNET TEXT MESSAGES", RFC 822, August 1982. [2] Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform Resource Locators (URL)", RFC 1738, December 1994. [3] Kindel, C., "The uuid: URI scheme", November 1997, . [4] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. [5] Moats, R., "URN Syntax", RFC 2141, May 1997. [6] Goland, Y., Whitehead, E., Faizi, A., Carter, S. and D. Jensen, "HTTP Extensions for Distributed Authoring -- WEBDAV", RFC 2518, February 1999. [7] International Organization for Standardization, "ISO/IEC 11578:1996 Information technology -- Open Systems Interconnection -- Remote Procedure Call", August 2001. Stickler Expires July 17, 2002 [Page 6] Internet-Draft The hrn: URI Scheme January 2002 Author's Address Patrick Stickler Nokia Research Center Visiokatu 1 Tampere 33720 FI EMail: patrick.stickler@nokia.com Stickler Expires July 17, 2002 [Page 7] Internet-Draft The hrn: URI Scheme January 2002 Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. 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