Internet DRAFT - draft-snell-additional-link-relations
draft-snell-additional-link-relations
Network Working Group J. Snell
Internet-Draft January 8, 2013
Intended status: Informational
Expires: July 12, 2013
Additional Link Relation Types
draft-snell-additional-link-relations-07
Abstract
This specification defines a number of additional Link Relation Types
that can used for a range of purposes in a variety of applications
types.
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 July 12, 2013.
Copyright Notice
Copyright (c) 2013 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 July 12, 2013 [Page 1]
Internet-Draft Additional Link Relations January 2013
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. "about" . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. "preview" . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. "privacy-policy" . . . . . . . . . . . . . . . . . . . . . . . 3
4.1. The "privacy-policy" Link Relation and P3P . . . . . . . . 4
5. "terms-of-service" . . . . . . . . . . . . . . . . . . . . . . 5
6. "type" . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
8. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
9. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7
Snell Expires July 12, 2013 [Page 2]
Internet-Draft Additional Link Relations January 2013
1. Introduction
The fundamental model for Web Links and the Registry of Link
Relations are established by [RFC5988]. This specification defines
and adds the following additional link relation types to the
registry: about, preview, privacy-policy, terms-of-service, and type.
2. "about"
The "about" Link relation can be used to refer to a resource that is
the subject or topic 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: <http://store.example.org/product/abc>; rel="about"
{...}
3. "preview"
The "preview" Link relation can be used to refer to a resource that
serves as a preview of the link's context, likely with reduced
quality or limited content. For instance, the preview link might
reference a screen capture of a video, a brief snippet of audio from
a song or a thumbnail representation of an image.
For example, issuing a HTTP HEAD request to a URI representing a
large video or image file might return a link to a short or lower
quality preview of the original:
HTTP/1.1 200 OK
Content-Text: video/mpeg
Link: <http://example.org/preview/10-second-preview.mpg>;
rel="preview"; type="video/mpeg"
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
Snell Expires July 12, 2013 [Page 3]
Internet-Draft Additional Link Relations January 2013
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:
HTTP/1.1 200 OK
Content-Type: text/html
<html>
<head>
...
<link rel="privacy-policy" href="/privacy-policy.html" />
...
</head>
<body>
...
</body>
</html>
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 can only be interpreted as
a description of the expected practice.
It is recommended that publishers of privacy policy resources linked
to using the "privacy-policy" Link relation 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. How
much mechanisms are utilized are out of the scope of this
specification, however.
4.1. The "privacy-policy" Link Relation and P3P
The Platform for Privacy Preferences (P3P [1]) is a W3C
Recommendation that defines a data format for the expression of
privacy policy information. While the "privacy-policy" link relation
can be used to reference P3P documents, there is no intended
relationship, normative or otherwise between this specification and
the P3P Recommendation. As far as this specification is concerned,
P3P Documents are just one possible type of resource "privacy-policy"
links can reference.
Snell Expires July 12, 2013 [Page 4]
Internet-Draft Additional Link Relations January 2013
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:
HTTP/1.1 200 OK
Content-Type: text/html
<html>
<head>
...
<link rel="terms-of-service" href="/tos.html">
...
</head>
<body>
...
</body>
</html>
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: <http://example.org/Person/givenName>; rel="type"
Sally
When used within the header of an HTTP message, the "type" specified
by the type link relation cannot be confused with the content type of
the payload as given by the Content-Type header. The "type" link
relation references the payload's abstract semantic type whereas the
Snell Expires July 12, 2013 [Page 5]
Internet-Draft Additional Link Relations January 2013
Content-Type header identifies the specific serialization format of
the payload.
If the context can be considered to be an instance of multiple
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, Section 2
o Relation Name: preview
o Description: Refers to a resource that provides a preview of the
link's context.
o Reference: This specification, Section 3
o Relation Name: privacy-policy
o Description: Refers to a Privacy Policy associated with the link's
context.
o Reference: This specification, Section 4
o Relation Name: terms-of-service
o Description: Refers to the Terms of Service associated with the
link's context.
o Reference: This specification, Section 5
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, Section 6
8. Security Considerations
There are no additional security concerns introduced by this
document.
9. Normative References
[RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010.
Snell Expires July 12, 2013 [Page 6]
Internet-Draft Additional Link Relations January 2013
[1] <http://www.w3.org/P3P/>
Author's Address
James M Snell
Email: jasnell@gmail.com
Snell Expires July 12, 2013 [Page 7]
