WWW2005 Devday Link Microformats

John Allsopp

Western Civilisation pty. ltd :: westciv

What are link Microformats?

a set of microformats that capture the relationship between web resources, using the rel attribute of html.

The rel attribute of HTML

most of us will be familiar with this attribute from style sheets

<link rel="stylesheet" href="style.css">

the rel attribute

"describes the relationship from the current document to the anchor specified by the href attribute. The value of this attribute is a space-separated list of link types"

Possible values of the rel attribute are specified by the HTML spec and include stylesheet, alternate, next, chapter, appendix

Extending rel

rel may be extended according to the HTML specification

"Authors may wish to define additional link types not described in this specification. If they do so, they should use a profile to cite the conventions used to define the link types."

Link microformats use an XMDP to specify values for the rel attribute.

Three link microformats

  1. relLicense
  2. relTag
  3. XFN - XHTML Friends Network


By adding rel="license" to a hyperlink, a page indicates that the destination of that hyperlink is license for the current page. E.g. with the following hyperlink:

<a href="http://creativecommons.org/licenses/by/2.0/" rel="license">cc by 2.0</a>

the author indicates that the page is licensed under a Creative Commons 2.0 Attribution Required license.

Very similar to how rel is used explicitly in the HTML specification, for document to document relationships.

XMDP for relLicense

<dl class="profile">
 <dt id="rel">rel</dt>
   <a rel="help"
     HTML4 definition of the 'rel' attribute.</a>  
   Here is an additional value.</p>
   <dt id="license">license</dt>
   <dd>Indicates that the referred resource is a license
   for the referring page.</dd>

relTag microformat

relTag captures behavior associated with tagging and folksonomies

[any material that should appear in print but not on the slide]

Tagging and Folksonomies


Think of a tag as a simple category name. People can categorize their posts, photos, and links with any tag that makes sense

by tagging you build folksonomies


Folksonomy is a neologism for a practice of collaborative categorization using freely chosen keywords. More colloquially, this refers to a group of people cooperating spontaneously to organize information into categories, noted because it is almost completely unlike traditional formal methods of faceted classification

Taxonomic classification

Taxonomic classification

is the act of placing an object or concept into a set of categories (such as a taxonomy or a subject index), based on the properties of the object or concept. A person may classify the object or concept according to an ontology.

Examples of taxonomic classification include:

  • Library classification
  • Scientific classification of organisms


Why is tagging interesting?

Tagging in action

Flikr and Delicious

Flickr tags are added by content creators, and by invited others

Delicious tags are added by readers to bookmarks about posts

Both of these require the use of the system itself to tag content.

Decentralized tagging



Tagging is in pages under the developers complete control.

Can be utilized by tools, such as Moveable Type, WordPress, and more.

Web wide aggregate clouds


Not just English


relTag, a microformat for tagging

relTag enables decentralized tagging, not associated with any particular system or service.

By adding rel="tag" to a hyperlink, a page indicates that the destination of that hyperlink is an author-designated "tag" (or keyword/subject) of the current page. Using this link

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

the author indicates that the page has the tag "tech".

Tag spaces

The link should be to a tag space, and to a page which exists.

A Tag space is a place that collates or defines tags, where the last component of the URL is the tag, e.g.
is a URL for the tag "tech".

Tag spaces may be hosted at any domain. This works with many existing sites such as Wikipedia and Flickr.

Different kinds of relationship with rel

Principle of microformats

Microformats formalize existing practice, rather than establish new practices

adapt to current behaviors and usage patterns, e.g. (X)HTML, blogging

Bloggers have long been linking to other blogs, and treating destination blogs as a representation of the person who created that blog.

Similarly, bloggers have for some time been making explicit the relationship between themselves and the creators of other blogs.

XFN is a microformat to capture these relationships in a more formal way.

A very brief intro to XFN

XFN enables relationships between people to be explicitly stated, using the rel attribute of a link.

As an example, we all could say:
<a href="http://tantek.org" rel="met">
because we have physically met Tantek

I might say:
<a href="http://tantek.org" rel="friend">
because I consider him a friend (and hope the rev is true :-)

Wrap up

What are link Microformats?

a set of microformats that capture the relationship between web resources, using the rel attribute of html.

Different kinds of relationship