%PDF-1.2 %âãÏÓ 8 0 obj > stream BT 72 638.28 TD 0 0 0 rg /F0 9.96 Tf 0.024 Tc 0 Tw (Internet-Draft) Tj 168 0 TD (The tag: URI scheme) Tj 204 0 TD (March 2001) Tj -92.04 -36 TD (Tim Kindberg) Tj -279.96 -12 TD (Internet Draft) Tj 279.96 0 TD (Hewlett-Packard Corp.) Tj -279.96 -12 TD (Document: draft-kindberg-tag-uri-00.txt) Tj 0 -12 TD (Expires: September 1, 2001) Tj 279.96 0 TD (March 2001) Tj -111.96 -48 TD (The tag: URI scheme) Tj -186 -36 TD (STATUS OF THIS MEMO) Tj 18 -24 TD (This document is an Internet-Draft and is in full conformance with all) Tj 0 -12 TD (provisions of Section 10 of RFC2026.) Tj 0 -24 TD (Internet-Drafts are working documents of the Internet Engineering Task) Tj 0 -12 TD (Force \(IETF\), its areas, and its working groups. Note that other) Tj T* (groups may also distribute working documents as Internet-Drafts.) Tj 0 -24 TD (Internet-Drafts are draft documents valid for a maximum of six months and) Tj 0 -12 TD (may be updated, replaced, or ) Tj 174 0 TD (obsoleted by other documents at any time. It) Tj -174 -12 TD (is inappropriate to use Internet-Drafts as reference material or to cite) Tj 0 -12 TD (them other than as "work in progress.") Tj 0 -24 TD (The list of current Internet-Drafts can be accessed at) Tj 0 -12 TD ( http://www.ietf.org/ietf/1id-abstracts.txt) Tj T* (The list of Internet-Draft Shadow Directories can be accessed at) Tj T* ( http://www.ietf.org/shadow.html.) Tj 0 -24 TD (This Internet-draft will expire on September 1, 2001.) Tj T* (Copyright Notice Copyright \(C\) The Internet Society \(2001\). All Rights) Tj 0 -12 TD (Reserved.) Tj -18 -36 TD (ABSTRACT) Tj 18 -24 TD (This document describes the 'tag:' Uniform Resource Identifier \(URI\)) Tj 0 -12 TD (scheme for identifiers that are unique across space and time. Identifiers) Tj T* (belonging to this scheme are distinct from most other ) Tj 324 0 TD (URIs in that they) Tj -324 -12 TD (are intended for use that is independent of any particular method for) Tj 0 -12 TD (resource location or name resolution. A 'tag:' URI may be used purely as) Tj T* (an identifier that distinguishes one entity from another. It may also be) Tj T* (presented to services for resolution into a web resource or into one or) Tj T* (more further ) Tj 78 0 TD (URIs, but no particular resolution scheme is implied or) Tj ET endstream endobj 9 0 obj 2342 endobj 4 0 obj > /ProcSet 2 0 R >> /Contents 8 0 R >> endobj 11 0 obj > stream BT 72 638.28 TD 0 0 0 rg /F0 9.96 Tf 0.024 Tc 0 Tw (Internet-Draft) Tj 168 0 TD (The tag: URI scheme) Tj 204 0 TD (March 2001) Tj -372 -43.2 TD (preferred by a 'tag:' identifier itself. Unlike ) Tj 288 0 TD (UUIDs or ) Tj 54 0 TD (GUIDs such as) Tj -342 -12 TD (') Tj 6 0 TD (uuid:' and ') Tj 72 0 TD (urn:oid' ) Tj 54 0 TD (URIs, which also have some of the above properties,) Tj -132 -12 TD ('tag:' identifiers are designed to be tractable to humans. Furthermore,) Tj 0 -12 TD (they have many of the desirable properties that 'http:' URLs have when) Tj T* (used as identifiers, but none of the drawbacks.) Tj 0 -36 TD (Table of Contents) Tj 21.6 -24.72 TD /F0 12 Tf 0 Tc (Status of this Memo) Tj 140.4 0 TD (................................) Tj 230.4 0 TD (................) Tj 118.32 0 TD (1) Tj -489.12 -13.56 TD (Abstract) Tj 61.2 0 TD (................................) Tj 230.4 0 TD (...........................) Tj 197.52 0 TD (1) Tj -489.12 -13.68 TD (The 'tag:' URI scheme) Tj 154.8 0 TD (................................) Tj 230.4 0 TD (..............) Tj 103.92 0 TD (3) Tj -453.12 -12.12 TD /F1 9.96 Tf 0.0076 Tc 0.0224 Tw (Transfers of domain names) Tj 0 -11.52 TD 0.06 Tc 0 Tw (4) Tj -37.56 -11.52 TD 0.0257 Tc (Equality) Tj 34.32 0 TD 0.03 Tc (................................) Tj 80.64 0 TD (................................) Tj 80.64 0 TD (................................) Tj 80.64 0 TD (................................) Tj 80.64 0 TD (................................) Tj 80.64 0 TD (.....................) Tj 55.32 0 TD 0.06 Tc (5) Tj -491.28 -12.84 TD /F0 12 Tf 0 Tc (Security Considerations) Tj 169.2 0 TD (................................) Tj 230.4 0 TD (............) Tj 89.52 0 TD (5) Tj -489.12 -13.68 TD (References) Tj 75.6 0 TD (................................) Tj 230.4 0 TD (.........................) Tj 183.12 0 TD (6) Tj -489.12 -13.56 TD (Author's Address) Tj 118.8 0 TD (................................) Tj 230.4 0 TD (...................) Tj 139.92 0 TD (6) Tj -528.72 -26.4 TD /F0 9.96 Tf 0.024 Tc (INTRODUCTION) Tj 18 -24 TD (A 'tag:' identifier is a type of Uniform Resource Identifier \(URI\) [X]) Tj 0 -12 TD (designed to meet the following requirements:) Tj 0 -24 TD (1\) Identifiers are unique across space and time and come from a) Tj 0 -12 TD (practically inexhaustible supply;) Tj T* (2\) identifiers are convenient for humans to read, type etc.;) Tj T* (3\) zero registration cost, at least to current holders of a registered) Tj T* (domain name, and negligible cost to mint new identifiers;) Tj T* (4\) easy identification of the ) Tj 180 0 TD (organisation that has minted the identifier,) Tj -180 -12 TD (should that be desirable;) Tj 0 -12 TD (5\) no commitment to any particular resource-location or identifier-) Tj T* (resolution scheme.) Tj 0 -24 TD (The above requirements obtain in the case that a user wants to place) Tj 0 -12 TD (identifiers on their documents.) Tj 0 -24 TD (1\) They want to be sure that the identifier is unique. Global uniqueness) Tj 0 -12 TD (is valuable because it guarantees that one identifier cannot conflict with) Tj T* (another, whatever the scope of future sharing.) Tj T* (2\) The user would like the identifier to be tractable to humans: they) Tj T* (should be able to type it into a form; it could contain a hint about how) Tj T* (to ) Tj 18 0 TD (categorise the document, or the date of issue.) Tj ET endstream endobj 12 0 obj 3474 endobj 10 0 obj > /ProcSet 2 0 R >> /Contents 11 0 R >> endobj 16 0 obj > stream BT 72 638.28 TD 0 0 0 rg /F0 9.96 Tf 0.024 Tc 0 Tw (Internet-Draft) Tj 168 0 TD (The tag: URI scheme) Tj 204 0 TD (March 2001) Tj -372 -36 TD (3\) They do not want to have to communicate with anyone else in order to) Tj 0 -12 TD (create identifiers for their documents.) Tj T* (4\) It is natural to use a name associated with the user or their) Tj T* (organisation within the identifier, since that is the origin of the) Tj T* (identifier.) Tj T* (5\) As good net citizens, the user does not want to use an identifier that) Tj T* (might be assumed by software to imply the existence of a corresponding) Tj T* (resource in a default binding scheme \226 so that an attempt to retrieve that) Tj T* (resource is likely but doomed to failure. Of course, this leaves them free) Tj T* (to exploit the identifier in particular applications and services, where) Tj T* (the context is clear.) Tj 0 -24 TD (Existing identification schemes satisfy some but not all of the general) Tj 0 -12 TD (requirements 1-5. For example:) Tj 0 -24 TD (UUIDs [X] are hard for humans to read and the assigning ) Tj 336 0 TD (organisation is) Tj -336 -12 TD (not explicit.) Tj 0 -24 TD (OIDs [x] and ) Tj 78 0 TD (DOIs [x] both require naming authorities to register) Tj -78 -12 TD (themselves, even if they already hold a domain name registration.) Tj 0 -24 TD (URNs [x] are intended to be resolvable in a default naming context.) Tj 0 -12 TD (Software encountering a URN in a document is liable to attempt to resolve) Tj T* (it, even though the identifier has not registered any resource in that) Tj T* (context.) Tj 0 -24 TD (URLs \(in particular, 'http:' URLs\) are sometimes used as ersatz) Tj 0 -12 TD (identifiers that satisfy most of our requirements. Many users and) Tj T* (organisations have already registered a domain name, and the use of the) Tj T* (domain name to mint identifiers comes at no additional cost. But there are) Tj T* (several drawbacks to URLs-as-identifiers:) Tj T* (A\) Many pieces of software might try to ) Tj 240 0 TD (dereference a URL-as-identifier,) Tj -240 -12 TD (even though there is no resource at the 'location'.) Tj 0 -12 TD (B\) We can't find out who minted a URL-as-identifier, if the domain has) Tj T* (changed hands. If Smith registers champignon.net and then Jones registers) Tj T* (it, no-one can tell who minted http://champignon.net/99.) Tj T* (C\) The new holder of a domain name can't be sure that they are minting new) Tj T* (names. Using the example from \(B\), how can Jones know, in general, whether) Tj T* (Smith has already used http://champignon.net/99?) Tj -18 -36 TD (THE 'TAG:' URI SCHEME) Tj 18 -24 TD (The general form of a 'tag:' URI is:) Tj ET endstream endobj 17 0 obj 2708 endobj 15 0 obj > /ProcSet 2 0 R >> /Contents 16 0 R >> endobj 19 0 obj > stream BT 72 638.28 TD 0 0 0 rg /F0 9.96 Tf 0.024 Tc 0 Tw (Internet-Draft) Tj 168 0 TD (The tag: URI scheme) Tj 204 0 TD (March 2001) Tj -314.4 -42 TD (tag:nameSpace:specific) Tj -57.6 -24 TD (Where:) Tj 57.6 -12 TD (nameSpace) Tj 57.6 0 TD (= ) Tj 12 0 TD (domainName) Tj 72 0 TD (DateQualifier>) Tj -141.6 -12 TD (domainName ) Tj 115.2 0 TD (= any well-formed domain name [x]) Tj -115.2 -12 TD (dateQualifier ) Tj 115.2 0 TD (= year | ) Tj 54 0 TD (year.month | ) Tj 78 0 TD (year.month) Tj 60 0 TD (.day) Tj -307.2 -12 TD (year) Tj 115.2 0 TD (= [2-9]) Tj 42 0 TD ([0-9][0-9][0-9]) Tj -157.2 -12 TD (month ) Tj 115.2 0 TD (= 0[1-9]|[1-12]) Tj -115.2 -12 TD (day ) Tj 115.2 0 TD (= 0[1-9]|[1-31]) Tj -115.2 -12 TD (specific) Tj 115.2 0 TD (= any string that makes the URI well-formed) Tj -172.8 -12 TD ([x]) Tj 0 -24 TD (') Tj 6 0 TD (nameSpace' is the name space part of the URI: it is a well-formed, domain) Tj -6 -12 TD (name registered to the entity that has minted the URI, optionally post-) Tj 0 -12 TD (fixed by a date qualifier.) Tj 0 -24 TD ('specific' is the name-space-specific part of the URI: it is any string of) Tj 0 -12 TD (valid URI characters chosen by the minter of the tag.) Tj 0 -24 TD (For example:) Tj 57.6 -24 TD (tag:hpl.hp.com:tst.1234567890) Tj 0 -12 TD (tag:exploratorium.edu:pi.99) Tj T* (tag:myIDs.com:TimKindberg/doc.101) Tj T* (tag:champignon.net:99) Tj T* (tag:champignon.net/2001.3.2:99) Tj T* (tag:champignon.net/2001.04:100) Tj T* (tag:champignon.net/2002:docs/research/99) Tj -57.6 -24 TD (Anyone who holds the current registration to a domain name has the right) Tj 0 -12 TD (to mint identifiers rooted at that name, as long as the domain name is) Tj T* (date-qualified, should that be necessary for uniqueness \(see 'transfers of) Tj T* (domain names'\).) Tj 0 -24 TD (For example, Hewlett-Packard Laboratories holds the registration for) Tj 0 -12 TD (hpl.hp.com and can mint any tag ) Tj 192 0 TD (URIs rooted at that name; but they may not) Tj -192 -12 TD (mint names under domain names not registered to them, such as) Tj 0 -12 TD (champignon.net.) Tj -18 -24 TD (TRANSFERS OF DOMAIN NAMES) Tj 18 -12 TD (The 'tag:' scheme copes with transfers of a domain name's registration) Tj 0 -12 TD (from one party to another. The ') Tj 192 0 TD (dateQualifier' is used to guarantee) Tj -192 -12 TD (uniqueness of ') Tj 90 0 TD (nameSpace' across several registrations of the domain.) Tj ET endstream endobj 20 0 obj 2472 endobj 18 0 obj > /ProcSet 2 0 R >> /Contents 19 0 R >> endobj 22 0 obj > stream BT 72 638.28 TD 0 0 0 rg /F0 9.96 Tf 0.024 Tc 0 Tw (Internet-Draft) Tj 168 0 TD (The tag: URI scheme) Tj 204 0 TD (March 2001) Tj -372 -48 TD (For example, an ) Tj 96 0 TD (organisation or individual that knows itself to be the) Tj -96 -12 TD (first registrant of champignon.net can mint names of the form) Tj 0 -12 TD (tag:champignon.net:...) Tj 0 -24 TD (However, in some cases the domain will change hands. For example, suppose) Tj 0 -12 TD (that on March 2, 2001, the champignon.net domain registration becomes held) Tj T* (by a new entity. That entity must date-qualify the domain name to ensure) Tj T* (that its tag name space is unique. It must postfix the full date \(day,) Tj T* (month, year\) during the month of March; it must postfix at lease the month) Tj T* (and year during the remainder of that year; it must postfix at least the) Tj T* (year subsequently.) Tj 0 -24 TD (An alternative to date qualification would be ordinal-qualification: the) Tj 0 -12 TD (second registrant of champignon.net could use the name space) Tj T* (champignon.net.2; the third champignon.net.3, etc. However, no mechanism) Tj T* (exists for tracking that ) Tj 150 0 TD (ordinality. The advantage of date qualification) Tj -150 -12 TD (is that each registrant knows its responsibilities and relies on no other) Tj 0 -12 TD (agency for correct namespace designation.) Tj -18 -24 TD (EQUALITY OF TAGS) Tj 18 -24 TD (Two tag ) Tj 48 0 TD (URIs are equal if and only if:) Tj -12 -12 TD (their name space identifiers match and) Tj 0 -12 TD (their specific identifiers are identical, including their case.) Tj -36 -24 TD (Two tag name space identifiers match if their canonical forms match, where) Tj 0 -12 TD (their canonical form is obtained by reducing upper case characters to) Tj T* (lower case and removing leading zeros from date components.) Tj 0 -24 TD (Thus, tag:champignon.net.2.3.2001:99 and tag:champignon.net.4.2001:99 are) Tj 0 -12 TD (unequal, as are tag:champignon.net.2002:test and) Tj T* (tag:champignon.net.2002:Test.) Tj 0 -24 TD (But the following two tags are equal: tag:CHAMPIGNON.NET:99 and) Tj 0 -12 TD (tag:champignon.net:99) Tj -18 -36 TD (SECURITY CONSIDERATIONS) Tj 18 -24 TD (No mechanism can prevent an ) Tj 168 0 TD (organisation from using another's domain name.) Tj -168 -12 TD (A malicious party could pollute another party's tag name space. Only the) Tj 0 -12 TD (threat of legal action counts against that.) 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