existing-rel-values
existing rel values
This page contains tables of known 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.
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.
Sources:
- W3C HTML 4 link type
- Proposed HTML4 link type
- GRDDL spec
- xfn microformat
- other microformats
| 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 (1) | the referenced person is a child of the person represented by the current document | XFN |
| child (2) | the target document is a hierarchical child, or subdocument, of the current document | Proposed HTML4 link type |
| 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 (1) | the referenced person is a parent of the person represented by the current document | XFN |
| parent (2) | the target document is the hierarchical parent, or container, of the current document | Proposed HTML4 link type |
| 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 (1) | the referenced person is a sibling of the person represented by the current document | XFN |
| sibling (2) | the target document is a child of a common parent, or a hierarchical peer of the current document | Proposed HTML4 link type |
| 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 asrel="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) |
|---|---|---|---|
| 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 | |
| replies | … indicates a continued thread | rel-replies | RFC4685 |
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.
| rel value | summary | brainstormed in |
|---|---|---|
| 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 |
| member | the referenced document represents a member of the group represented by the current document | group-brainstorming |
| product | … | product-brainstorming |
| profile | … | xmdp-brainstorming |
| (various) | XFN values for family relationships | genealogy-brainstorming#Relationships |
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:
- Meta Information in DevMo Docs (DevMo)
- Microsummary
- Web Communication Link Relationships (WCLR)
- W3C Link Relationship values draft (LRdraft) - from a draft of the HTML spec circa 1991.
- HTML5 draft Liable to change
| rel value | summary | origin | proposal(s) |
|---|---|---|---|
| archive | index of archived entries | 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 |
| comment | … | … | WCLR |
| contribution | … | … | WCLR |
| details | … | (seen on w3c.org news log in a "read more" permalink) | … |
| 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 |
| feed | Gives the address of a syndication feed for the current document. | … | WCLR/ HTML5 |
| icon | Imports an icon to represent the current document. (Allowed in link only) |
… | WCLR/ HTML5 |
| lightbox | … | (Google search for rel=lightbox in the wild) | … |
| made | … | … | LRdraft |
| meta | … | (seen on w3c.org - citation needed) | … |
| microsummary | … | … | Microsummary, be aware of: microsummary issues |
| 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 |
| 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.
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.
Sources: HTML3 (expired!) - (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.)
| 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). | HTML 3 | unknown |
| up | When the document forms part of a hierarchy, this link references the immediate parent of the current document. | HTML 3 | unknown, but proposed for re-introduction in HTML5 |
rejected
Some rel values have been proposed and rejected. These are not recommended for use in microformats, and listed here to make that explicit.
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].
- 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. Unfortunately the use of Dublin Core in user visible content like<a href>appears to be strictly theoretical.
- At first glance it appears the results from the search show only uses with the invisible
- http://www.ietf.org/rfc/rfc2731.txt - also has
rel="schema.AC"andrel="schema.RC"with the patternrel="schema.PREFIX".
to-do
- Proposed HTML4 link types
- begin: identifies the author-defined start of a sequence of documents of which the current document is a node. TOP is a functional equivalent to BEGIN when only one of these values is specified.
- bibliography: identifies a bibliography
- biblioentry: identifies a bibliographic entry
- citation: the target is a bibliographic citation
- collection: the target document is an COLLECTION that contains the current document
- definition: identifies a definition of a term
- disclaimer: identifies a hypertext link to a legal disclaimer
- editor: identifies a hypertext link to an editor
- end: identifies the author-defined end of a sequence of documents of which the current document is a node. TOP is a functional equivalent to END when only one is specified
- first: synonym for BEGIN
- footnote: the anchor is a footnote marker and the target is a footnote
- last: synonym for end
- meta: identifies a hypertext link to a node which contains meta-information related to the current document
- 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
- origin: alternative to "top"
- 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 [c/f hAudio]
- publisher: identifies a hypertext link to a publisher
- sibling: the target document is a child of a common parent, or a hierarchical peer of the current document
- top: the target document is the logical top node of the tree (see also BEGIN)
- trademark: identifies a hypertext link to a trademark notice
- translation: the target is a translation to another language
- urc: identifies a Universal Resource Citation
The above were not adopted, but might be reused in future microformats.
tools
See implementations.