Network Working Group J. Snell Internet-Draft May 15, 2012 Intended status: Standards Track Expires: November 16, 2012 Additional Link Relation Types draft-snell-additional-link-relations-04 Abstract This specification defines a number of additional Link Relation Types that can used for a variety of purposes.. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on November 16, 2012. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Snell Expires November 16, 2012 [Page 1] Internet-Draft Additional Link Relations May 2012 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. "about" . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. "preview" . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. "privacy-policy" . . . . . . . . . . . . . . . . . . . . . . . 3 5. "terms-of-service" . . . . . . . . . . . . . . . . . . . . . . 4 6. "type" . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 9.1. Normative References . . . . . . . . . . . . . . . . . . . 6 9.2. Informative References . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 Snell Expires November 16, 2012 [Page 2] Internet-Draft Additional Link Relations May 2012 1. Introduction This specification defines a number of additional Link Relation Types for a variety of common linking scenarios. 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]. 2. "about" The "about" Link relation can be used to refer to a resource that is the subject of the link's context. Multiple subjects can be indicated through the use of multiple "about" link relations. For example, if the context resource is a review about a particular product, the "about" link can be used to reference the URL of the product: HTTP/1.1 200 OK Content-Type: application/json Link: ; rel="about" {...} 3. "preview" The "preview" Link relation can be usd to refer to a resource that serves as a preview of the link's context, for instance, a screen capture of a video, or a brief snippet of audio from a song. 4. "privacy-policy" The "privacy-policy" Link relation can be used to refer to a resource describing the privacy policy associated with the link's context. The privacy policy can be any resource that discloses what personal information about the user is collected, and how that personal information is stored, used, managed and disclosed to other parties. For example, an HTTP server that collects personal information about a user throughout the course of the user's interaction with the service can include "privacy-policy" Links within all HTTP Responses using any combination of Link headers or links embedded in the response payload: Snell Expires November 16, 2012 [Page 3] Internet-Draft Additional Link Relations May 2012 An example showing various locations where privacy-policy links can potentially appear: HTTP/1.1 200 OK Content-Type: text/html Link: ; rel="privacy-policy" ... ... ... Privacy Policy ... Note that in the absence of clear legal obligations placed on an entity either through contract or law, the presence of a "privacy- policy" Link does not constitute a legally binding obligation on the part of the service. The linked resource MUST be interpreted as only a description of the expected practice. Publishers of privacy policy resources linked to using the "privacy- policy" Link relation type SHOULD provide a clear and simple mechanism for signaling when changes to the Privacy Policy resource have been made, such as generating a new Entity Tag for the resource or generating a hash over the Privacy Policy's content. 5. "terms-of-service" The "terms-of-service" Link relation can be used to refer to a resource describing the Terms of Service associated with the link's context. The Terms of Service can be any resource that describes the rules to which a consumer of the service must agree to follow when using the service provided by the link's context. For example, an HTTP server can include "terms-of-service" Links within all HTTP Responses using any combination of Link headers or links embedded in the response payload: Snell Expires November 16, 2012 [Page 4] Internet-Draft Additional Link Relations May 2012 An example showing various places where terms-of-service links can potentially appear: HTTP/1.1 200 OK Content-Type: text/html Link: ; rel="terms-of-service" ... ... ... Privacy Policy ... It must be noted that the Terms of Service linked to using this link relation carries no legal weight and can be ignored with impunity in the absence of an explicit, legally enforceable contract. The linked Terms of Service are simply a notice of the terms that may be expected to apply once a contract is established. 6. "type" The "type" Link relation can be used to indicate that the context resource is an instance of the resource identified by the target IRI. HTTP/1.1 200 OK Content-Type: text/plain Link: ; type="type" Sally Note that, when used within an HTTP message as in the example, the "type" specified by the type link relation MUST NOT be confused with the media type of the payload itself as given by the Content-Type header. The "type" link relation references the payload's abstract semantic type whereas the Content-Type header identifies the specific serialization format of the payload. If the context can be considered to be an instance of multiple Snell Expires November 16, 2012 [Page 5] Internet-Draft Additional Link Relations May 2012 semantic types, multiple "type" link relations can be used. 7. IANA Considerations The Registry of Link Relations should be updated with the following entries: o Relation Name: about o Description: Refers to a resource that is the subject of the link's context. o Reference: This specification. o Relation Name: preview o Description: Refers to a resource that provides a preview of the link's context. o Reference: This specification. o Relation Name: privacy-policy o Description: Refers to a Privacy Policy associated with the link's context. o Reference: This specification. o Relation Name: terms-of-service o Description: Refers to the Terms of Service associated with the link's context. o Reference: This specification. o Relation Name: type o Description: Refers to a resource identifying the abstract semantic type the link's context is considered to be an instance of. o Reference: This specification. 8. Security Considerations There are no additional security concerns introduced by this document. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Snell Expires November 16, 2012 [Page 6] Internet-Draft Additional Link Relations May 2012 9.2. Informative References [RFC5023] Gregorio, J. and B. de hOra, "The Atom Publishing Protocol", RFC 5023, October 2007. [RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010. Author's Address James M Snell Email: jasnell@gmail.com Snell Expires November 16, 2012 [Page 7]