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Snell 3 Internet-Draft January 8, 2013 4 Intended status: Informational 5 Expires: July 12, 2013 7 Additional Link Relation Types 8 draft-snell-additional-link-relations-07 10 Abstract 12 This specification defines a number of additional Link Relation Types 13 that can used for a range of purposes in a variety of applications 14 types. 16 Status of this Memo 18 This Internet-Draft is submitted to IETF in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at http://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on July 12, 2013. 33 Copyright Notice 35 Copyright (c) 2013 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 51 2. "about" . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 52 3. "preview" . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 4. "privacy-policy" . . . . . . . . . . . . . . . . . . . . . . . 3 54 4.1. The "privacy-policy" Link Relation and P3P . . . . . . . . 4 55 5. "terms-of-service" . . . . . . . . . . . . . . . . . . . . . . 5 56 6. "type" . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 57 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 58 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 59 9. Normative References . . . . . . . . . . . . . . . . . . . . . 6 60 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 62 1. Introduction 64 The fundamental model for Web Links and the Registry of Link 65 Relations are established by [RFC5988]. This specification defines 66 and adds the following additional link relation types to the 67 registry: about, preview, privacy-policy, terms-of-service, and type. 69 2. "about" 71 The "about" Link relation can be used to refer to a resource that is 72 the subject or topic of the link's context. Multiple subjects can be 73 indicated through the use of multiple "about" link relations. 75 For example, if the context resource is a review about a particular 76 product, the "about" link can be used to reference the URL of the 77 product: 79 HTTP/1.1 200 OK 80 Content-Type: application/json 81 Link: ; rel="about" 83 {...} 85 3. "preview" 87 The "preview" Link relation can be used to refer to a resource that 88 serves as a preview of the link's context, likely with reduced 89 quality or limited content. For instance, the preview link might 90 reference a screen capture of a video, a brief snippet of audio from 91 a song or a thumbnail representation of an image. 93 For example, issuing a HTTP HEAD request to a URI representing a 94 large video or image file might return a link to a short or lower 95 quality preview of the original: 97 HTTP/1.1 200 OK 98 Content-Text: video/mpeg 99 Link: ; 100 rel="preview"; type="video/mpeg" 102 4. "privacy-policy" 104 The "privacy-policy" Link relation can be used to refer to a resource 105 describing the privacy policy associated with the link's context. 106 The privacy policy can be any resource that discloses what personal 107 information about the user is collected, and how that personal 108 information is stored, used, managed and disclosed to other parties. 110 For example, an HTTP server that collects personal information about 111 a user throughout the course of the user's interaction with the 112 service can include "privacy-policy" Links within all HTTP Responses 113 using any combination of Link headers or links embedded in the 114 response payload: 116 HTTP/1.1 200 OK 117 Content-Type: text/html 119 120 121 ... 122 123 ... 124 125 126 ... 127 128 130 Note that in the absence of clear legal obligations placed on an 131 entity either through contract or law, the presence of a "privacy- 132 policy" Link does not constitute a legally binding obligation on the 133 part of the service. The linked resource can only be interpreted as 134 a description of the expected practice. 136 It is recommended that publishers of privacy policy resources linked 137 to using the "privacy-policy" Link relation provide a clear and 138 simple mechanism for signaling when changes to the Privacy Policy 139 resource have been made, such as generating a new Entity Tag for the 140 resource or generating a hash over the Privacy Policy's content. How 141 much mechanisms are utilized are out of the scope of this 142 specification, however. 144 4.1. The "privacy-policy" Link Relation and P3P 146 The Platform for Privacy Preferences (P3P [1]) is a W3C 147 Recommendation that defines a data format for the expression of 148 privacy policy information. While the "privacy-policy" link relation 149 can be used to reference P3P documents, there is no intended 150 relationship, normative or otherwise between this specification and 151 the P3P Recommendation. As far as this specification is concerned, 152 P3P Documents are just one possible type of resource "privacy-policy" 153 links can reference. 155 5. "terms-of-service" 157 The "terms-of-service" Link relation can be used to refer to a 158 resource describing the Terms of Service associated with the link's 159 context. The Terms of Service can be any resource that describes the 160 rules to which a consumer of the service must agree to follow when 161 using the service provided by the link's context. 163 For example, an HTTP server can include "terms-of-service" Links 164 within all HTTP Responses using any combination of Link headers or 165 links embedded in the response payload: 167 HTTP/1.1 200 OK 168 Content-Type: text/html 170 171 172 ... 173 174 ... 175 176 177 ... 178 179 181 It must be noted that the Terms of Service linked to using this link 182 relation carries no legal weight and can be ignored with impunity in 183 the absence of an explicit, legally enforceable contract. The linked 184 Terms of Service are simply a notice of the terms that may be 185 expected to apply once a contract is established. 187 6. "type" 189 The "type" Link relation can be used to indicate that the context 190 resource is an instance of the resource identified by the target IRI. 192 HTTP/1.1 200 OK 193 Content-Type: text/plain 194 Link: ; rel="type" 196 Sally 198 When used within the header of an HTTP message, the "type" specified 199 by the type link relation cannot be confused with the content type of 200 the payload as given by the Content-Type header. The "type" link 201 relation references the payload's abstract semantic type whereas the 202 Content-Type header identifies the specific serialization format of 203 the payload. 205 If the context can be considered to be an instance of multiple 206 semantic types, multiple "type" link relations can be used. 208 7. IANA Considerations 210 The Registry of Link Relations should be updated with the following 211 entries: 213 o Relation Name: about 214 o Description: Refers to a resource that is the subject of the 215 link's context. 216 o Reference: This specification, Section 2 218 o Relation Name: preview 219 o Description: Refers to a resource that provides a preview of the 220 link's context. 221 o Reference: This specification, Section 3 223 o Relation Name: privacy-policy 224 o Description: Refers to a Privacy Policy associated with the link's 225 context. 226 o Reference: This specification, Section 4 228 o Relation Name: terms-of-service 229 o Description: Refers to the Terms of Service associated with the 230 link's context. 231 o Reference: This specification, Section 5 233 o Relation Name: type 234 o Description: Refers to a resource identifying the abstract 235 semantic type the link's context is considered to be an instance 236 of. 237 o Reference: This specification, Section 6 239 8. Security Considerations 241 There are no additional security concerns introduced by this 242 document. 244 9. Normative References 246 [RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010. 248 [1] 250 Author's Address 252 James M Snell 254 Email: jasnell@gmail.com