RDFa: an introduction

RDFa: an introduction

Kai Li
LIS 681 Metadata

What is RDFa?
• RDFa = RDF in attributes
• RDFa Core is a “specification for attributes to
express structured data in any markup
language.”
– Including (X)HTML and XML and other languages
– HTML/XML tree structure is used
– Some attributes and text content is reused from
HTML/XML.

RDFa, Microformats and Microdata

For full comparison, see: http://manu.sporny.org/2011/uber-comparison-rdfa-md-uf/

RDFa, Microformats and Microdata
(cont.)
• Google supports all three formats.
• The latest Schema.org initiated by Google,
Bing and Yahoo! chose Microdata over RDFa.
• However, the approach of Schema.org is
“Microdata and more”, which means the
vocabularies in Schema.org can be mixed with
other approaches.

It’s about integrating RDF triples into
HTML
<http://nalsi.net/posts/20130124135526.html>
<http://purl.org/dc/elements/1.1/creator>
<http://nalsi.us/about#me>
<http://nalsi.net/posts/20130124135526.html>
<http://purl.org/dc/terms/created>
“2013/01/24”

<div resource=“http://nalsi.net/posts/20130124135526.html”>
<p>Written by: <span
property=“http://purl.org/dc/elements/1.1/creator”>Kai</span><
/p>
<p>Time: <span
property=“http://purl.org/dc/terms/created”>2013-01-
24</span></p>
</div>

RDFa: datatypes
• CURIE(s): compact URI(s), being composed of
a prefix and astring.
– For example: <div about="dbr:Albert_Einstein">
• IRIs: Internationalized Resource Identifiers,
which is an extension of the URI or URL, in
which internationalized characters are allowed
to use.

How to use RDFa: tags
• @about
• @resource
• @property
• @href
• @vocab
• @prefix
• @content
• @typeof
• And more tags…

@about and @resource
• Both attributes can serve to set the subject of
the following statements.
– The difference is, @about can be only used for
setting subject.
– @resource, when combined with attribute
“property”, can be used to set the target, the
object, for the statement.

@about and @resource (cont.)
Example 1:
<ul>
<li about="/alice/posts/trouble_with_bob" property="title">The trouble
with Bob</li>
<li about="/alice/posts/jos_barbecue" property="title">Jo's Barbecue</li> ...
</ul>

Example 2:
<div about="http://dbpedia.org/resource/Albert_Einstein">
<div rel="dbp:birthPlace"
resource="http://dbpedia.org/resource/German_Empire">
<span property="dbp:conventionalLongName">the German
Empire</span>
</div></div>

@property
• The relationship between the subject and
either an object if given or some literal text.

Example:
<body>
<h2 property="http://purl.org/dc/terms/title">The Trouble with Bob</h2>
</body>

@href
• The partner resource of a relationship
(object).

Example:
<head>
<link rel="prev" href="page6.html" />
</head>

@prefix and @vocab
• Both of these two attributes define the
namespace of the names used in the
structured data.
– @prefix defines the prefix of the value that will be
used; @vocab defines the default URL of the
vocabulary.

@prefix and @vocab, cont.
Example 1:
<div vocab="http://xmlns.com/foaf/0.1/" about="#me">
My name is <span property="name">John Doe</span> and my
blog is called
<a rel="homepage"
href="http://example.org/blog/">Understanding Semantics</a>.
</div>

Example 2:
This document is licensed under the
<a prefix="cc: http://creativecommons.org/ns#" rel="cc:license"
href="http://creativecommons.org/licenses/by-nc-nd/3.0/" >Creative
Commons By-NC-ND License</a>.

@content
• A string, to supply machine-readable content
for a literal.

Example:
<head>
<meta property="http://purl.org/dc/terms/creator" content="Mark Birbeck"
/>
</head>

@typeof
• RDF type(s) to associate with a subject.

Example:
<span about="urn:ISBN:0091808189" typeof="bibo:Book"
property="dc:title">Canteen Cuisine</span>

RDFa Use Cases
• W3C published the official RDFa Use Case in
2007 as a draft.
– http://www.w3.org/TR/xhtml-rdfa-scenarios/
• The document explores “how publishers, tool
builders, and consumers benefit from RDFa”
by embedding RDF in HTML.
• Nine use cases are listed and discussed.

RDFa Use Cases, cont.
• Publishers
– Mark the web pages with structured data so that
machines can consume these contents
• Tool builders
– Augment the metadata embedded in the HTML
files to facilitate using the data
• Users
– Better organize, sort and categorize related
information on the Internet

RDFa Use Cases, cont.
• Use Case Example:
– Sarah is a information scientist who publishes her
recent study about metadata standards in her
personal website. She uses RDFa to “mark up” this
website, so that the results of the study as well as
her rights toward the study can be not only
meaningful to human readers, but also to
machines.

Reference
• Birbeck, M. (2009, June 23). Introduction to RDFa.
Retrieved April 1, 2013, from
http://alistapart.com/article/introduction-to-rdfa
• Brickley, D. (2012, June 7). SemTech, RDFa,
Microdata and more... Retrieved April 1, 2013,
from http://blog.schema.org/2012/06/semtech-
rdfa-microdata-and-more.html
• Sporny, M. (2013, February 23). An Uber-
comparison of RDFa, Microdata and
Microformats. Retrieved April 1, 2013, from
http://manu.sporny.org/2011/uber-comparison-
rdfa-md-uf/

Reference, cont.
• W3C. (2012, June 7). RDFa 1.1 Primer. Retrieved
April 1, 2013, from http://www.w3.org/TR/xhtml-
rdfa-primer/
• W3C. (2012, June 7). RDFa Core 1.1. Retrieved
March 31, 2013, from
http://www.w3.org/TR/2012/REC-rdfa-core-
20120607/
• W3C. (2007, March 30). RDFa Use Cases:
Scenarios for Embedding RDF in HTML. Retrieved
April 1, 2013, from http://www.w3.org/TR/xhtml-
rdfa-scenarios/

RDFa: an introduction

Recomendados

Recomendados

Más contenido relacionado

La actualidad más candente

La actualidad más candente (20)

Similar a RDFa: an introduction

Similar a RDFa: an introduction (20)

Más de Kai Li

Más de Kai Li (20)

Último

Último (20)

RDFa: an introduction