HTML and CSS Reference
In-Depth Information
Microformats
A special approach to metadata is a set of simple open data formats called
microformats
(mF). They are highly
correlated with the Semantic Web by applying and reusing features of existing technologies (for example, the (X)
HTML
rel
attribute) and by introducing new ones with the simplest approaches possible—based on
Plain Old
Semantic HTML
(
POSH
) (for example, hCard). They can be applied not only in (X)HTML markup but also in XML,
RSS, Atom, and so on.
Microformats can express site structure, link weight, content type, and human relationships with the
class
,
rel
,
and
rev
attribute values [27]. They are very easy to write, and the number of software supporting them is increasing
(for example, the Operator [28] and Tails Export [29] add-ons for Firefox, the Michromeformats Google Chrome
extension [30], the microformats transformer Optimus [31], or the Microformats Bookmarklet for Safari, Firefox,
and IE [32]).
However, there are still some open issues. For example, applying various microformats as multiple values on the
a
element should be avoided (for example,
rel="nofollow"
and
rel="friend"
). The
rev
attribute used by the Vote
Links microformat cannot be used in HTML5.
Profile URIs provided by the
profile
attribute cannot be used on the
head
element in HTML5, where the
profile
attribute values can be declared for the
rel
attribute on anchors (
a
) or link elements (
link
). As an example, a profile
URI is presented for the hCalendar microformat with all the three options. The hCalendar microformat is based on
the iCalendar standard (RFC 2445 [33]). All contents that use hCalendar notation should refer to the hCalendar XMDP
profile, in other words,
http://microformats.org/profile/hcalendar
, as shown in Listing 7-7 or Listing 7-8 for the
document head or in Listing 7-9 as part of the document body. These methods can also be combined.
Listing 7-7.
Providing the hCalendar Head Profile in the Document Head (Cannot Be Used in HTML5)
<head profile="
http://microformats.org/profile/hcalendar
"
>
Listing 7-8.
Linking to the hCalendar Profile in the Document Head
<link rel="profile" href="
http://microformats.org/profile/hcalendar
"
>
Listing 7-9.
Using the hCalendar Profile in the Document Body
<a rel="profile" href="
http://microformats.org/profile/hcalendar
"
>hCalendar</a>
New structural elements introduced by HTML5, such as
article
,
nav
, and
section
, are not recognized by certain
microformat parsers.
In the next sections, we will give you an overview of some of the most popular microformats, namely, hCalendar,
hCard,
rel="license"
,
rel="nofollow"
,
rel="tag"
, Vote Links, and XFN.
hCalendar
You can use the hCalendar microformat to create calendar entries for sport events, anniversaries, reminders,
meetings, workshops, conferences, and other events. The root class name for hCalendar is
vcalendar
. The root class
name for events is
vevent
, which is required for all event listings.
The properties are represented by the elements of hCalendar. The required properties are
dtstart
, which should
be provided in the ISO date format,
2
and
summary
.
2
Beyond microformats such as hAtom, hCalendar, hCard, and hReview, several web technologies apply the ISO 8601 date format
for date-time representation, such as XML, XML schema datatypes, RDF, and Atom.
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