Metadata and the Semantic Web - Web Standards: Mastering HTML5, CSS3, and XML - page 241

rel=“tag”
The rel="tag" is still a draft specification since 2005 [43]. Unlike other microformats and general meta keywords, this
microformat can be used for visible links. It can be applied on hyperlink elements to indicate that the destination of
the link is a general author-designated tag (keyword) for the current page.
Within this microformat, spaces can be provided either as + or as %20 . Unicode characters are encoded according
to the generic syntax rules of URIs described by the Internet Society (RFC 3986 [44]).
Vote Links
Vote Links is an elemental microformat with three possible values on the rev attribute of the a element: vote-for ,
vote-against , and vote-abstain . The values are mutually exclusive. Optionally, visible rollovers can be provided by
the title attribute. Listing 7-18 shows an example.
Listing 7-18. A Vote Links Example
<a rev="vote-for" href="http://example.com/thumbsup/" 
title="HTML should be the primary markup language">HTML5</a>
<a rev="vote-against" href="http://example.com/thumbsdown/" 
title="XHTML should be the primary markup language">XHTML5</a>
Initially, the draft specification applied Vote Links on the rel attribute, which is now deprecated [45].
Listing 7-19 shows the URI profile reference.
Listing 7-19. The URI Profile for Vote Links
<link rel="profile" href=" http://microformats.org/profile/vote-links ">
XFN
The very first HTML microformat, XHTML Friends Network (XFN), was introduced in December 2003 [46]. XFN was
designed by Global Multimedia Protocols Group to express human relationships with simple hyperlinks [47]. XFN is
especially useful for brochure-style home pages and blog entries.
The name of the person should be provided as the text of the hyperlink (between <a> and </a> ). The personal
web site is the target of the hyperlink, in other words, the value of the href attribute. All relationship data can be
provided by the rel attribute on a elements. Multiple values are allowed and should be separated by spaces. The
friendship type can be contact , acquaintance , or friend . If the person is known personally, it can be expressed
by the met attribute value of the rel attribute. For example, a friend of Leslie Sikos whom he knows personally can
publish that relationship on his web site by XFN, as shown in Listing 7-20.
Listing 7-20. Link to the Web Site of a Friend
I am an old friend of <a href=" http://lesliesikos.com " rel="friend met" >Leslie Sikos</a>.
The distance between the residence of the person and that of his friend can be expressed by the co-resident
and neighbor values. Relatives can set to child , parent , sibling , spouse , or kin . The professional relationships
co-worker and colleague are also supported. Feelings can also be expressed ( muse , crush , date , sweetheart ) [48].
CSS styles can also be added to XFN metadata. For example, friends can be provided in bold and colleagues in
italic with the CSS rules shown in Listing 7-21.