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<h1> rel-tag </h1>
{{DISPLAYTITLE:rel="tag"}}
<span style="float:right">__TOC__</span>
== Draft Specification 2005-01-10 ==
* If you’re looking for <code>rel="me"</code>, see: '''[[rel-me]]'''.


__TOC__
== Draft Specification 2005-01-10 ==
; Editors/Authors
; Editors/Authors
:[http://tantek.com/ Tantek Çelik]
:[http://tantek.com/ Tantek Çelik]
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:[http://powazek.com/ Derek Powazek]
:[http://powazek.com/ Derek Powazek]


;Incorporated into
:[https://www.w3.org/TR/html5/links.html#link-type-tag W3C HTML5]
=== Copyright ===
=== Copyright ===
{{MicroFormatCopyrightStatement2004}}
{{MicroFormatCopyrightStatement2004}}
* [[User:Tantek|Tantek]]: I release all my contributions to this specification into the public domain and I encourage the other authors to do so as well.
* [[User:Tantek|Tantek]]: I release all my contributions to this specification into the public domain and I encourage the other authors to do so as well.
* [[User:Kevin Marks|Kevin Marks]]: I release all my contributions to this specification into the public domain and I encourage the other authors to do so as well.
** When all authors/editors have done so, we can remove the MicroFormatCopyrightStatement template reference and replace it with the MicroFormatPublicDomainContributionStatement.
** When all authors/editors have done so, we can remove the MicroFormatCopyrightStatement template reference and replace it with the MicroFormatPublicDomainContributionStatement.


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[[Rel-Tag]] is one of several [[MicroFormats]].  By adding <code>rel=&quot;tag&quot;</code> to a hyperlink, a page indicates that the destination of that hyperlink is an author-designated &quot;tag&quot; (or keyword/subject) for the current page. Note that a tag may just refer to a major portion of the current page (i.e. a blog post). e.g. by placing this link on a page,
[[Rel-Tag]] is one of several [[MicroFormats]].  By adding <code>rel=&quot;tag&quot;</code> to a hyperlink, a page indicates that the destination of that hyperlink is an author-designated &quot;tag&quot; (or keyword/subject) for the current page. Note that a tag may just refer to a major portion of the current page (i.e. a blog post). e.g. by placing this link on a page,


<pre><nowiki><a href=&quot;http://technorati.com/tag/tech&quot; rel=&quot;tag&quot;>tech</a></nowiki></pre>
<syntaxhighlight lang="html"><a href="http://technorati.com/tag/tech" rel="tag">tech</a></syntaxhighlight>


the author indicates that the page (or some portion of the page) has the tag &quot;tech&quot;.
the author indicates that the page (or some portion of the page) has the tag &quot;tech&quot;.
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is the text of the tag, so  
is the text of the tag, so  


<pre><nowiki><a href=&quot;http://technorati.com/tag/tech&quot; rel=&quot;tag&quot;>fish</a></nowiki></pre>
<syntaxhighlight lang="html"><a href="http://technorati.com/tag/tech" rel="tag">fish</a></syntaxhighlight>


would indicate the tag &quot;tech&quot; rather than &quot;fish&quot;.
would indicate the tag &quot;tech&quot; rather than &quot;fish&quot;.
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rel=&quot;tag&quot; is NOT designed for &quot;tagging&quot; arbitrary URLs or external content.  There is demand for a general decentralized syntax for tagging URLs external to the current page, but this is not meant for that.  See [[xfolk|xFolk]] and [[hreview|hReview]] for ways to tag arbitrary URLs.
rel=&quot;tag&quot; is NOT designed for &quot;tagging&quot; arbitrary URLs or external content.  There is demand for a general decentralized syntax for tagging URLs external to the current page, but this is not meant for that.  See [[xfolk|xFolk]] and [[hreview|hReview]] for ways to tag arbitrary URLs.


If you need to define tags as part of a more specialized format,  rel=&quot;tag&quot; is the recommended way to do so, and [[xfolk|xFolk]], [[hreview|hReview]], [[hcard |hCard]] and [[hcalendar|hCalendar]] all do this.
If you need to define tags as part of a more specialized format,  rel=&quot;tag&quot; is the recommended way to do so, and [[xfolk|xFolk]], [[hreview|hReview]], [[hcard |hCard]], [[hcalendar|hCalendar]] and [[hrecipe|hRecipe]] all do this.
 
== XMDP profile ==
== XMDP profile ==
<pre><nowiki>
See [[rel-tag-profile]].
<dl class=&quot;profile&quot;>
<dt id=&quot;rel&quot;>rel</dt>
<dd><p>
  <a rel=&quot;help&quot; href=&quot;http://www.w3.org/TR/html401/struct/links.html#adef-rel&quot;>
    HTML4 definition of the 'rel' attribute.</a> 
  Here is an additional value.</p>
  <dl>
  <dt id=&quot;tag&quot;>tag</dt>
  <dd>Indicates that the referred resource serves as a &quot;tag&quot;,
      or keyword/subject, for the referring page.</dd>
  </dl>
</dd>
</dl>
</nowiki></pre>


== Tag Spaces ==
== Tag Spaces ==


Tags are embedded in HTTP URIs in a well-defined manner so that the tag embedded in an HTTP URI can be mechanically extracted from that URI. Specifically, the last segment of the path portion of the URI (after the final "/" character) contains the tag value. For example, the URI <pre><nowiki>http://www.example.com/tags/foo</nowiki></pre> contains the tag &quot;foo&quot;.  
Tags are embedded in HTTP URIs in a well-defined manner so that the tag embedded in an HTTP URI can be mechanically extracted from that URI. Specifically, the last segment of the path portion of the URI (after the final "/" character) contains the tag value. For example, the URI <syntaxhighlight lang="html">http://www.example.com/tags/foo</syntaxhighlight> contains the tag &quot;foo&quot;.  


Thus, for the purposes of comparing two HTTP URIs as tags, the last segment of the path portion should be extracted and only that value (that value of the tag) should be compared.
Thus, for the purposes of comparing two HTTP URIs as tags, the last segment of the path portion should be extracted and only that value (that value of the tag) should be compared.
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The destination of a rel=&quot;tag&quot; hyperlink is required to be a tag space (a place that collates or defines tags), where the last segment of the path of the URL is the tag, e.g.  
The destination of a rel=&quot;tag&quot; hyperlink is required to be a tag space (a place that collates or defines tags), where the last segment of the path of the URL is the tag, e.g.  


<pre><nowiki>http://technorati.com/tag/tech </nowiki></pre>
<syntaxhighlight lang="html">http://technorati.com/tag/tech</syntaxhighlight>


is a URL for the tag &quot;tech&quot;.
is a URL for the tag &quot;tech&quot;.
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Tags may only be placed in the URL path, and only in the last segment of the path.  Tags may not be placed in query parameters or fragment identifiers.  e.g.
Tags may only be placed in the URL path, and only in the last segment of the path.  Tags may not be placed in query parameters or fragment identifiers.  e.g.


<pre><nowiki>http://technorati.com/tag/tech?tag=fish#emu </nowiki></pre>
<syntaxhighlight lang="html">http://technorati.com/tag/tech?tag=fish#emu</syntaxhighlight>


is still a URL for the tag &quot;tech&quot;, not &quot;fish&quot; or &quot;emu&quot;.
is still a URL for the tag &quot;tech&quot;, not &quot;fish&quot; or &quot;emu&quot;.
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Since the only part of a tag space URL of which any structure is required is the last path segment, a tag space URL can be hosted at any domain.  Authors may choose to link to a tag at a particular tag space in order to provide a specific meaning.  E.g. a tag for technology could link to:
Since the only part of a tag space URL of which any structure is required is the last path segment, a tag space URL can be hosted at any domain.  Authors may choose to link to a tag at a particular tag space in order to provide a specific meaning.  E.g. a tag for technology could link to:


<pre><nowiki>  http://en.wikipedia.org/wiki/Technology </nowiki></pre>
<syntaxhighlight lang="html">  http://en.wikipedia.org/wiki/Technology</syntaxhighlight>


Trailing slashes in tag URLs are ignored, that is:
Trailing slashes in tag URLs are ignored, that is:


<pre><nowiki>  http://technorati.com/tag/Technology/ </nowiki></pre>
<syntaxhighlight lang="html">  http://technorati.com/tag/Technology/</syntaxhighlight>
as a rel-tag URL is treated as:
as a rel-tag URL is treated as:
<pre><nowiki>  http://technorati.com/tag/Technology </nowiki></pre>
<syntaxhighlight lang="html">  http://technorati.com/tag/Technology</syntaxhighlight>


== Encoding issues ==
== Encoding issues ==
Spaces can be encoded either as <code>+</code> or <code>%20</code>. Unicode characters are encoded as specified in [http://www.ietf.org/rfc/rfc3986.txt RFC 3986]. For example:
Spaces can be encoded either as <code>+</code> or <code>%20</code>. Unicode characters are encoded as specified in [http://www.ietf.org/rfc/rfc3986.txt <nowiki>RFC 3986</nowiki>]. For example:


<pre><nowiki><a href=&quot;http://technorati.com/tag/Sant%C3%A9+et+bien-%C3%AAtre&quot; rel=&quot;tag&quot;>Santé et bien-être</a> </nowiki></pre>
<syntaxhighlight lang="html"><a href="http://technorati.com/tag/Sant%C3%A9+et+bien-%C3%AAtre" rel="tag">Santé et bien-être</a></syntaxhighlight>


Note that if using Wikipedia as a tagspace, as discussed above, you should use <code>%20</code> as they remap '+' to <code>%2B</code>, causing  a page with a plus sign in the title (which usually does not exist) to appear.
Note that if using Wikipedia as a tagspace, as discussed above, you should use <code>%20</code> as they remap '+' to <code>%2B</code>, causing  a page with a plus sign in the title (which usually does not exist) to appear.
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As a result the invisible tag link syntax variant: <code><link rel=&quot;tag&quot; href=&quot;...&quot; /></code> SHOULD NOT be supported by implementations.
As a result the invisible tag link syntax variant: <code><link rel=&quot;tag&quot; href=&quot;...&quot; /></code> SHOULD NOT be supported by implementations.


==Examples in the Wild==
== Examples in the wild ==
This section is '''informative'''.
This section is '''informative'''. The number of rel-tag examples in the wild has expanded far beyond the capacity of being kept inline in this specification. They have been moved to a [[rel-tag-examples-in-wild|separate page]].
 
The following sites have implemented rel-tag, and thus are a great place to start for anyone looking for examples "in the wild" to try parsing, indexing, organizing etc. If your site marked up with rel-tag, feel free to add it to the '''top''' of this list. Once the list grows too big, we'll make a separate wiki page.


* [http://www.keevu.com Keevu.com] uses rel-tag to indicate content categories on most pages, like [http://www.keevu.com/venues venues]
See [[rel-tag-examples-in-wild|rel-tag Examples in the wild]].
* [http://www.amazingincredible.com Amazing Incredible] uses rel-tag on content pages
* [http://www.auctionlink.com.au AuctionLink] uses rel-tag on [http://www.auctionlink.com.au/TagList/Auctioneers/ Auction Sales Listings] tags.
** Could also use [[hcard|hCard]], e.g. on [http://www.auctionlink.com.au/Auctioneers/Auctioneer/Bonhams_Goodman_1/] [[User:AndyMabbett|Andy Mabbett]]
* Christian Hess uses rel-tag on his [http://www.hess-cr.com homepage blog] and several other pages of his site.
* [http://spacedust.atspace.com/ Spacedust] uses rel-tag to mark up gallery pages.
* [http://my.opera.com/dstorey/blog/ My Opera] uses rel-tag for tags on all user's blog entries.
* [http://dev.opera.com/articles/view/making-wii-friendly-pages/ Dev Opera] uses rel-tag on all article tags.
* [http://www.international.unt.edu UNT International] uses rel-tag to indicate content categories on most pages
* [http://yedda.com Yedda] - Yedda publishes rel-tags for all of the tags the people entered on themselves as well as on all tags entered on questions asked on Yedda.
* [http://www.lingr.com Lingr] publishes rel-tags for all user entered tags.
* [http://odeo.com ODEO] [http://odeo.com/blog/2005/07/adding-microformats-to-odeo.html publishes] rel-tags for user entered tags.
* [http://eventful.com Eventful] publishes rel-tags for user entered tags.
* [http://spinn3r.com Spinn3r] implements rel-tag as well as RSS and Atom subject and categories.


== Implementations ==
== Implementations ==
This section is '''informative'''.
This section is '''informative'''.


The following implementations have been developed which either generate or parse rel-tag links. If you have a rel-tag implementation, feel free to add it to the '''top''' of this list. Once the list grows too big, we'll make a separate wiki page.
The following implementations have been developed which either generate or parse rel-tag links. If you have a rel-tag implementation, please add it to the '''top''' of this list. Once the list grows too big, we'll make a separate wiki page like [[rel-tag-implementations]].


* [http://degoli.dajbych.net Degoli] is a simple experimental semantic web seach engine which is crawling rel-tag data. It orders search results by rel-tag data and displays a navigation tree containing relationships among tags.
* [http://b2evolution.net b2evolution] A blog platform which generates rel-tag for all tags on blog posts (starting from v3.x).
* [http://www.textcube.org Textcube.org] makes a blogging tool, Textcube which generates rel-tag for tags on blog posts.
* [http://hashtags.org/ HashTags] tags Twitter posts, converting "#example" into a tag of "example"
* [http://hashtags.org/ HashTags] tags Twitter posts, converting "#example" into a tag of "example"
* [http://ikiwiki.info ikiwiki] generates rel-tag for all tagged pages (as of version 2.6)
* [http://ikiwiki.info ikiwiki] generates rel-tag for all tagged pages (as of version 2.6)
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* The Freetag plugin for the [http://www.s9y.org Serendipity] blog software supports rel-tags on a per-entry basis, as well as inside of its tag clouds.  (The Freetag plugin is available inside of SPARTACUS)
* The Freetag plugin for the [http://www.s9y.org Serendipity] blog software supports rel-tags on a per-entry basis, as well as inside of its tag clouds.  (The Freetag plugin is available inside of SPARTACUS)
* [http://placenamehere.com/TXP/pnh_mf/ pnh_mf] is a plugin for [http://textpattern.com/ Textpattern] that supports embedding rel-tags and other microformats in templates and blog posts. Written by [http://placenamehere.com/ Chris Casciano].
* [http://placenamehere.com/TXP/pnh_mf/ pnh_mf] is a plugin for [http://textpattern.com/ Textpattern] that supports embedding rel-tags and other microformats in templates and blog posts. Written by [http://placenamehere.com/ Chris Casciano].
* [http://www.truist.com/blog/493/trutags-a-tagging-plugin-for-textpattern tru_tags] is a plugin for [http://textpattern.com/ Textpattern] that supports rel-tagging blog posts via the Keywords field.
* [http://www.rainskit.com/blog/493/trutags-a-tagging-plugin-for-textpattern tru_tags] is a plugin for [http://textpattern.com/ Textpattern] that supports rel-tagging blog posts via the Keywords field.
* [http://clothesonline.info ClothesOnline] uses rel-tag for categorizing shops and brands, for example: [http://clothesonline.info/brands/canada-goose Canada Goose].
* [http://news.livejournal.com/86492.html?thread=24881884 LiveJournal] - see also [http://www.livejournal.com/support/faq.bml?cat=tags their FAQ regarding their tags support]
* [http://news.livejournal.com/86492.html?thread=24881884 LiveJournal] - see also [http://www.livejournal.com/support/faq.bml?cat=tags their FAQ regarding their tags support]
* [http://trac.labnotes.org/cgi-bin/trac.cgi/wiki/TagsLinks TagsLinks] Turn each tag into links that let you find related content on tagging services.
* [http://trac.labnotes.org/cgi-bin/trac.cgi/wiki/TagsLinks TagsLinks] Turn each tag into links that let you find related content on tagging services.
* [http://www.octofinder.com OctoFinder] uses rel-tag for all live news tag clouds.
* [http://dev.wp-plugins.org/wiki/BunnysTechnoratiTags Tag plugin for WordPress]
* [http://dev.wp-plugins.org/wiki/BunnysTechnoratiTags Tag plugin for WordPress]
** Note that some sites using WordPress (http://microformatique.com/ for instance) are getting incorrect tags. The tag is ?cat=12 instead of the actual tag value.
** Note that some sites using WordPress (http://microformatique.com/ for instance) are getting incorrect tags. The tag is ?cat=12 instead of the actual tag value.
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* [http://consumingexperience.blogspot.com/2005/12/updated-multiple-word-technorati-tag.html Greasemonkey script for Firefox that generates tags for Blogger]
* [http://consumingexperience.blogspot.com/2005/12/updated-multiple-word-technorati-tag.html Greasemonkey script for Firefox that generates tags for Blogger]
* [http://tools.microformatic.com/help/xhtml/rel-lint/ rel-lint] is a validation tool by [[User:DrewMcLellan|Drew McLellan]] that will validate existence of rel-tag attributes.
* [http://tools.microformatic.com/help/xhtml/rel-lint/ rel-lint] is a validation tool by [[User:DrewMcLellan|Drew McLellan]] that will validate existence of rel-tag attributes.
== articles ==
This section is '''informative'''.
Articles about rel-tag, most recent first. When this section gets too big, we can move it to [[rel-tag-articles]].
* (undated) [http://reference.sitepoint.com/html/rel-mf#rel__tag SitePoint reference: rel- Microformats / tag] by Ian Lloyd


== References ==
== References ==
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==Related pages==
==Related pages==
{{rel-tag-related-pages}}
{{rel-tag-related-pages}}
[[Category:Specifications]]
[[Category:rel-tag]]

Latest revision as of 21:59, 13 November 2022

Draft Specification 2005-01-10

  • If you’re looking for rel="me", see: rel-me.
Editors/Authors
Tantek Çelik
Kevin Marks
Concept
Derek Powazek
Incorporated into
W3C HTML5

Copyright

This specification is (C) 2004-2024 by the authors. However, the authors intend to submit (or already have submitted, see details in the spec) this specification to a standards body with a liberal copyright/licensing policy such as the GMPG, IETF, and/or W3C. Anyone wishing to contribute should read their copyright principles, policies and licenses (e.g. the GMPG Principles) and agree to them, including licensing of all contributions under all required licenses (e.g. CC-by 1.0 and later), before contributing.

  • Tantek: I release all my contributions to this specification into the public domain and I encourage the other authors to do so as well.
  • Kevin Marks: I release all my contributions to this specification into the public domain and I encourage the other authors to do so as well.
    • When all authors/editors have done so, we can remove the MicroFormatCopyrightStatement template reference and replace it with the MicroFormatPublicDomainContributionStatement.

Patents

This specification is subject to a royalty free patent policy, e.g. per the W3C Patent Policy, and IETF RFC3667 & RFC3668.

Abstract

Rel-Tag is one of several MicroFormats. By adding rel="tag" to a hyperlink, a page indicates that the destination of that hyperlink is an author-designated "tag" (or keyword/subject) for the current page. Note that a tag may just refer to a major portion of the current page (i.e. a blog post). e.g. by placing this link on a page,

<a href="http://technorati.com/tag/tech" rel="tag">tech</a>

the author indicates that the page (or some portion of the page) has the tag "tech".

The linked page SHOULD exist, and it is the linked page, rather than the link text, that defines the tag. The last path component of the URL is the text of the tag, so

<a href="http://technorati.com/tag/tech" rel="tag">fish</a>

would indicate the tag "tech" rather than "fish".

Scope

rel="tag" is specifically designed for "tagging" content, typically web pages (or portions thereof, like blog posts).

rel="tag" is NOT designed for "tagging" arbitrary URLs or external content. There is demand for a general decentralized syntax for tagging URLs external to the current page, but this is not meant for that. See xFolk and hReview for ways to tag arbitrary URLs.

If you need to define tags as part of a more specialized format, rel="tag" is the recommended way to do so, and xFolk, hReview, hCard, hCalendar and hRecipe all do this.

XMDP profile

See rel-tag-profile.

Tag Spaces

Tags are embedded in HTTP URIs in a well-defined manner so that the tag embedded in an HTTP URI can be mechanically extracted from that URI. Specifically, the last segment of the path portion of the URI (after the final "/" character) contains the tag value. For example, the URI

http://www.example.com/tags/foo

contains the tag "foo".

Thus, for the purposes of comparing two HTTP URIs as tags, the last segment of the path portion should be extracted and only that value (that value of the tag) should be compared.

Need more formal language about comparison and extraction process.

The destination of a rel="tag" hyperlink is required to be a tag space (a place that collates or defines tags), where the last segment of the path of the URL is the tag, e.g.

http://technorati.com/tag/tech

is a URL for the tag "tech".

Tags may only be placed in the URL path, and only in the last segment of the path. Tags may not be placed in query parameters or fragment identifiers. e.g.

http://technorati.com/tag/tech?tag=fish#emu

is still a URL for the tag "tech", not "fish" or "emu".

Since the only part of a tag space URL of which any structure is required is the last path segment, a tag space URL can be hosted at any domain. Authors may choose to link to a tag at a particular tag space in order to provide a specific meaning. E.g. a tag for technology could link to:

  http://en.wikipedia.org/wiki/Technology

Trailing slashes in tag URLs are ignored, that is:

  http://technorati.com/tag/Technology/

as a rel-tag URL is treated as:

  http://technorati.com/tag/Technology

Encoding issues

Spaces can be encoded either as + or %20. Unicode characters are encoded as specified in RFC 3986. For example:

<a href="http://technorati.com/tag/Sant%C3%A9+et+bien-%C3%AAtre" rel="tag">Santé et bien-être</a>

Note that if using Wikipedia as a tagspace, as discussed above, you should use %20 as they remap '+' to %2B, causing a page with a plus sign in the title (which usually does not exist) to appear.

Tags Are Visible Metadata

rel="tag" hyperlinks are intended to be visible links on pages and posts. This is in stark contrast to meta keywords (which were invisible and typically never revealed to readers), and thus is at least somewhat more resilient to the problems which plagued meta keywords.

Making tag hyperlinks visible has the additional benefit of making it more obvious to readers if a page is abusing tag links, and thus providing more peer pressure for better behavior. It also makes it more obvious to authors, who may not always be aware what invisible metadata is being generated on their behalf.

As a result the invisible tag link syntax variant: <link rel="tag" href="..." /> SHOULD NOT be supported by implementations.

Examples in the wild

This section is informative. The number of rel-tag examples in the wild has expanded far beyond the capacity of being kept inline in this specification. They have been moved to a separate page.

See rel-tag Examples in the wild.

Implementations

This section is informative.

The following implementations have been developed which either generate or parse rel-tag links. If you have a rel-tag implementation, please add it to the top of this list. Once the list grows too big, we'll make a separate wiki page like rel-tag-implementations.

articles

This section is informative.

Articles about rel-tag, most recent first. When this section gets too big, we can move it to rel-tag-articles.

References

Normative References

  • HTML 4
  • XHTML 1
  • XMDP
  • RFC 3986 specifies URL syntax. Section 3.3 specifies URL paths and path segments.

Informative References

Discussions

Q&A

  • If you have any questions about rel-tag, check the rel FAQ first for general rel attribute questions, then check the rel-tag FAQ, and then if you don't find answers, ask your question on the microformats-discuss mailing list.

Related pages

The rel-tag specification is a work in progress. As additional aspects are discussed, understood, and written, they will be added. These thoughts, issues, and questions are kept in separate pages.