existing-rel-values

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<entry-title> existing rel values </entry-title>

This page contains tables of known HTML rel values from specifications, formats, proposals, brainstorms, and non-trivial POSH usage in the wild. In addition, dropped and rejected values are listed at the end for comprehensiveness.

usage: see how is 'rel' used. Regarding rev, see: should 'rev' even be used.

formats

These rel values are defined formats from specifications (HTML 4, microformats) are thus are recommended for general use. Alphabetically ordered by value.

Note:

  • Do not add rel values you find in the wild to this table of rel formats, instead add them to the table in the POSH section.
  • Do not add non-HTML rel values you find to this table of rel formats, instead add them to the table in the non HTML rel values section.
  • Do not add rel values from obsolete/superceded proposals or drafts, instead add them to the table in the "dropped" section.


Sources:

rel value summary
(from the relevant specification where possible))		 defining specification
acquaintance the person represented by the current document considers the person represented by the referenced document to be an acquaintance XFN
alternate Designates substitute versions for the document in which the link occurs. When used together with the lang attribute, it implies a translated version of the document. When used together with the media attribute, it implies a version designed for a different medium (or media). HTML4 link type
appendix Refers to a document serving as an appendix in a collection of documents. HTML4 link type
bookmark Refers to a bookmark. A bookmark is a link to a key entry point within an extended document. The title attribute may be used, for example, to label the bookmark. Note that several bookmarks may be defined in each document. HTML4 link type
chapter Refers to a document serving as a chapter in a collection of documents. HTML4 link type
child the referenced person is a child of the person represented by the current document XFN
colleague the referenced person is a colleague of the person represented by the current document XFN
contact the person represented by the current document considers the person represented by the referenced document to be a contact XFN
contents Refers to a document serving as a table of contents. Some user agents also support the synonym ToC (from "Table of Contents"). HTML4 link type
copyright Refers to a copyright statement for the current document. HTML4 link type
co-resident the referenced person lives in the same residence as the person represented by the current document XFN
co-worker the referenced person is a co-worker of the person represented by the current document XFN
crush this person considers the referenced person to be a crush (i.e. has a crush on the referenced person) XFN
date this person considers the referenced person to be a date (i.e. is dating the referenced person) XFN
friend the person represented by the current document considers the person represented by the referenced document to be a friend XFN
glossary Refers to a document providing a glossary of terms that pertain to the current document. HTML4 link type
help Refers to a document offering help (more information, links to other sources information, etc.) HTML4 link type
index Refers to a document providing an index for the current document. HTML4 link type
kin the referenced person is part of the extended family of the person represented by the current document XFN
license …indicates that the [referenced document] is a license for the current page. rel-license
me the referenced document represents the same person as does the current document XFN
met this person has met the referenced person XFN
muse the referenced person inspires the person represented by the current document XFN
neighbor the referenced person lives nearby the person represented by the current document XFN
next Refers to the next document in a linear sequence of documents. User agents may choose to preload the "next" document, to reduce the perceived load time. HTML4 link type
nofollow indicates that the destination of that hyperlink SHOULD NOT be afforded any additional weight or ranking by user agents which perform link analysis upon web pages (e.g. search engines). rel-nofollow
parent the referenced person is a parent of the person represented by the current document XFN
prev Refers to the previous document in an ordered series of documents. Some user agents also support the synonym "Previous". HTML4 link type
previous Synonym of prev HTML4 link type
section Refers to a document serving as a section in a collection of documents. HTML4 link type
sibling the referenced person is a sibling of the person represented by the current document XFN
spouse the referenced person is a spouse of the person represented by the current document XFN
start Refers to the first document in a collection of documents. This link type tells search engines which document is considered by the author to be the starting point of the collection. HTML4 link type
stylesheet a style sheet for the current document
used with the invisible <link href> element which is not ideal for content relationships. Content relationships should be user visible and thus uses with <a href> are strongly preferred. Unfortunately the use of stylesheet in user visible content like <a href> appears to be strictly theoretical.		 HTML4 link type
subsection Refers to a document serving as a subsection in a collection of documents. HTML4 link type
sweetheart this person considers the referenced person to be their sweetheart XFN
tag …indicates that the [referenced document] is an author-designated "tag" (or keyword/subject) for the current page. rel-tag
toc Synonym of contents (from "Table Of Contents") HTML4 link type
transformation Relates a source document to a transformation, usually represented in XSLT, that relates the source document syntax to the RDF graph syntax. Used in GRDDL GRDDL spec

notes

  • rel="alternate" can take further meaning from additional attributes, such as
    • rel="alternate" lang="fr" (French language version of this page)
    • rel="alternate" media="print" (printable version of this page)
    • rel="alternate" media="handheld" (version of the page intended or better for handheld/portable devices like PDAs, cell phones, etc.)
  • Synonyms such as "previous", "toc" are not as widely supported as the main term.

proposals

A few rel values have been developed as drafts as a result of going through most of the microformats process, and are thus listed here for your serious consideration. You may use these values, and if you find any problems with them please point them out on the respective "issues" page for the rel value.

rel value summary proposed in external spec (if any)
pronunciation …indicates that the destination of the 'link' element is a document providing a pronunciation lexicon for speech-synthesis purposes. rel-pronunciation
directory …indicates that the destination of the hyperlink is a directory listing containing an entry for the current page. rel-directory
enclosure …indicates that the destination of that hyperlink is intended to be downloaded and cached. rel-enclosure RFC4287
home …indicates that the [referenced document] is the homepage of the site in which the current page appears. rel-home
payment … rel-payment

brainstorming

Several rel values are being brainstormed as potential microformats and are thus listed here. If you find you have a use for such semantics in real world examples, consider trying out these values and provide feedback on the respective brainstorming page(s) with your results and experiences.

You may list new proposed rel values here, and even better if you can list and link to POSH uses in the wild.

rel value summary brainstormed in and usage in the wild
accessibility indicate[s] that the destination of that hyperlink contains accessibility information for the current page. blog post which itself uses the rel value in a <link> tag in the head of the document.
bibliography indicate[s] that the destination of that hyperlink is a bibliography for the current page. mailing list post, 2007-10-15
cite indicate[s] that the destination of that hyperlink is an authoritative source or a precedent to the current page. distributed-conversation-brainstorming
group the referenced document represents a group to which the person represented by the current document belongs group-brainstorming


longdesc Alternative to the img longdesc attribute, for use on visible links Google search for rel=longdesc in the wild shows many sources of proposals. Please edit this to list the earliest and perhaps most recent/comprehensive proposal. No known real world POSH usage in the wild yet.
map Link to a map. Possibly embedded within an adr, hCard, geo or hCalendar. Parsers MAY attempt to parse the URL if it is a link to a known map site (e.g. Geohash, Google Maps, Multimap) and extract co-ordinates and other useful data. (to TobyInk by email)
member the referenced document represents a member of the group represented by the current document group-brainstorming
product … product-brainstorming
profile indicate[s] that the destination of that hyperlink is a metadata profile (e.g. an XMDP profile) for the current page or portion thereof xmdp-brainstorming
shortlink the referenced document represents the current document but with a shorter URL blog post
vcalendar-parent link from an event to a containing event hCalendar 1.1 draft
vcalendar-child link from an event to a contained event hCalendar 1.1 draft
vcalendar-sibling link from an event to a related event with the same container hCalendar 1.1 draft
status the referenced document represents the status (or source of status updates) for the author of this document blog post

more brainstorming

See also:

POSH usage

There are numerous rel values used as POSH, both in the wild, whose origins are not necessarily known, nor are their meanings consistent. There are also numerous rel values from external proposals of varying degrees of merit. It is useful to document their existence and summarize their implied meanings/usage intent as research that may be used to perhaps take one or more of them thru the microformats process if there is both sufficient interest and sufficient in the wild usage.

Note: this list is incomplete, please help complete it from the following sources:

External sources:

rel value summary origin proposal(s)
apple-touch-icon Specify a Webpage Icon for a "Web Clip"; probably redundant with rel=icon Apple Safari Web Content Guide
apple-touch-startup-image Specify a splashscreen for Web apps on iOS Safari Apple Safari Web Content Guide


archive index of archived entrigs unknown, perhaps Wordpress open source blogging software WCLR
archives Provides a link to a collection of records, documents, or other materials of historical interest. HTML5
author … unknown DevMo / HTML5
canonical To help search engines disambiguate the same page with multiple representations Google Google/Microsoft/Yahoo!, Ask Jeeves


comment … … WCLR
contribution … … WCLR
EditURI … Seen in WordPress, e.g. [1] …
endorsed … … WCLR
external Indicates that the referenced document is not part of the same site as the current document. … HTML5
fan xxxx. … hcard-user-profile-authoring
feed Gives the address of a syndication feed for the current document. … WCLR/ HTML5
first Indicates that the current document is a part of a series, and that the first document in the series is the referenced document. … HTML5
icon Imports an icon to represent the current document. (Allowed in link only) HTML5 WCLR/HTML5
lightbox … (Google search for rel=lightbox in the wild) …
made … … LRdraft
meta … 1999 W3C RDF syntax REC FOAF
microsummary … … Microsummary, be aware of: microsummary issues
noreferrer indicates that no referrer information is to be leaked when following the link. HTML5 HTML5
openid.delegate … (Google search for rel=openid.* in the wild) …
openid.server … (Google search for rel=openid.* in the wild) …
permalink … … WCLR
pgpkey (see also rel-publickey) … [2], [3]
pingback Gives the address of the pingback server that handles pingbacks to the current document. (Allowed in link only) … WCLR/ HTML5
prefetch Specifies that the target resource should be pre-emptively cached. (Allowed in link only) … HTML5
publickey (see also rel-pgpkey) … [4]
referral … … WCLR
related … … WCLR
replies indicates a continued thread unknown RFC4685
resource … … WCLR
search … unknown unknown
sidebar Specifies that the referenced document, if retrieved, is intended to be shown in the browser's sidebar (if it has one). HTML5
sponsor … … WCLR
trackback … unknown, perhaps open source Movable Type blogging software WCLR
unendorsed (probably redundant to nofollow) … WCLR
up Provides a link to a document giving the context for the current document. … HTML5
user … … WCLR
via … … WCLR

WCLR

The WCLR proposal is described by its author (in e-mail, 2007-09-25) as:

…now effectively obsolete, since HTML5 and Microformats cover all the worthwhile relationships in that already.

These are covered by HTML5 already:

  • permalink -> bookmark
  • archive -> archives
  • feed
  • pingback
  • unendorsed -> nofollow

The rest now seem unnecessary.

Nonetheless, there may be some mileage in using them in microformats, at least until HTML5 is widely available.

HTML5 link type extensions

The following values are registered as link type extensions per the requirements in the WHATWG HTML spec and the requirements in the W3C HTML5 spec. Please make sure that registrations added here have all the required data filled in including "Effect on link", "Effect on a and area" and a link to a spec.

Keyword Effect on link Effect on a, area Brief description Link to specification Synonyms Status
shortcut External Resource Not allowed Used as a companion for icon for compatibility with IE. Documentation on MSDN Proposed

non HTML rel values

There are markup languages other than HTML that also have a rel attribute, often based upon the HTML rel attribute. It is useful to document some of these other languages and their rel values for both reference purposes, and to provide background research for the possible development and re-use of these values in HTML, as poshformats or microformats

Sources:

rel value summary
(from the relevant specification where possible))		 defining specification
self See http://www.rfc-editor.org/rfc/rfc4287.txt Atom
in-reply-to See http://code.google.com/apis/youtube/2.0/developers_guide_protocol_comments.html YouTube + Atom
... ... ...

dropped

The following rel values were in earlier version(s) of specification(s) and it is presumed by their absence from the most recent version of the respective specification(s) that they have been deprecated or obsoleted. Use of them could be considered a bit more standard than just POSH, although you may wish to research why such values were omitted from latter specifications before using them. If you do discover the reasoning, please add a short statement or link to thereof into the appropriate place in the following table.

In general, you SHOULD NOT use any dropped values.

In addition, if any such values have been superceded by standard values (see the first table on this page), then you MUST NOT use the dropped versions.

Sources:

  • HTML3 (HTML3) / has been superceded by HTML 3.2 - which itself has been superceded by HTML 4.0 - which itself has been updated by HTML 4.01, commonly referred to as "HTML 4" in this wiki and other places.)
  • Proposed HTML 4.0 link types (HTML4dropped) - obsoleted/superceded by the HTML 4.0 Recommendation. Any values that were in the "Proposed HTML 4.0 link types" document but didn't make it into the HTML 4.0 Recommendation were thus explicitly dropped and should `e avoided.
rel value summary defining specification why dropped
banner Was used to reference another document to be used as banner for this document (i.e. a form of "include" statement). HTML3 unknown
begin identifies the author-defined start of a sequence of documents of which the current document is a node. HTML4dropped unknown
biblioentry identifies a bibliographic entry HTML4dropped unknown
bibliography identifies a bibliography HTML4dropped unknown
child (obsolete/superceded) the target document is a hierarchical child, or subdocument, of the current document HTML4dropped unknown
citation the target is a bibliographic citation HTML4dropped unknown
collection the target document is an collection that contains the current document HTML4dropped unknown
definition identifies a definition of a term HTML4dropped unknown
disclaimer identifies a hypertext link to a legal disclaimer HTML4dropped unknown
editor identifies a hypertext link to an editor HTML4dropped unknown
end identifies the author-defined end of a sequence of documents of which the current document is a node. HTML4dropped unknown
first synonym for begin HTML4dropped unknown
footnote the anchor is a footnote marker and the target is a footnote HTML4dropped unknown
last synonym for end HTML4dropped unknown
navigate the target document contains information such as a image map that will help users to gain a sense of how and where to found information HTML4dropped unknown
origin synonym for top HTML4dropped unknown
parent (obsolete/superceded) the target document is the hierarchical parent, or container, of the current document HTML4dropped unknown
pointer the target is a pointer to the real target. This value can be used by a user agent to perform a pre-fetch of the specified target for evaluation until the real target is reached HTML4dropped unknown
publisher identifies a hypertext link to a publisher HTML4dropped unknown
sibling (obsolete/superceded) the target document is a child of a common parent, or a hierarchical peer of the current document HTML4dropped unknown
top the target document is the logical top node of the tree (see also begin) HTML4dropped unknown
trademark identifies a hypertext link to a trademark notice HTML4dropped unknown
translation the target is a translation to another language HTML4dropped unknown
up When the document forms part of a hierarchy, this link references the immediate parent of the current document. HTML3 unknown, but proposed for re-introduction in HTML5
urc identifies a Universal Resource Citation HTML4dropped unknown

rejected

Some rel values have been proposed and rejected. They are listed here to make that explicit. Authors MUST NOT use rejected rel values.

Source: rejected-formats.

rel value origin / proposal why rejected
pavatar pavatar rejected-formats#Pavatar

unspecified

Some rel values have been added to this page perhaps in one of the tables above, but no examples, nor an actual specification explicitly stating that the value(s) should be used in the HTML4 'rel' attribute could be found. They are listed here in the hopes someone can discover more specific/precise URLs to examples or specifications about them (preferably both). Until such precise URLs to examples/specs are provided, the values can be treated as they are purely theoretical and thus of little interest.

rel value "summary source
schema.DC … Dublin Core
schema.DCTERMS … Dublin Core

Notes:

  • Dublin Core. This search may help: [5].
    • examples from that search only use invisible <link href> element. At first glance it appears the results from the search show only uses with the invisible <link href> element which is not ideal for content relationships. Content relationships should be user visible and thus uses with <a href> are strongly preferred.
      • RFC2731 defines rel="schema.AC" and rel="schema.RC" with the pattern rel="schema.PREFIX" as a syntax for defining namespaces for use in meta[@name], *[@rel], *[@rev] and (as per eRDF) *[@class] attributes. A link to a Dublin Core metadata schema is generally not suitable for end users, so <link href> appears to be more appropriate than <a href> for those that use Dublin Core metadata schemas.
    • proposal to use in content currently only theoretical. Thus unfortunately the use of Dublin Core in user visible content like <a href> appears to be strictly theoretical. See microformats-discuss/2008-January/011445.html for a proposal to use Dublin Core in user visible content.

tools

See implementations.

related

copyright

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