Session 1/4. What RDFa. An introductory one day workshop on RDFa and its relevance, organised and delivered by Netskills.

1. Generic model for the provision of metadata
RDFa =
Resource Description Framework
in
attributes
HTML
What is RDFa?

2. What is RDFa
Session 1/4

3. Metadata
It’s all about metadata
‣ data about data
‣ many and varied versions of metadata
‣ add background information, put things in context, add value, make much
more useful by showing relevance
‣ different levels of metadata—may need pointer to further information to fully
explain a piece of metadata or describe how to interpret
‣ enable ways of classifying, connecting, rating, structuring, promoting, that
wouldn't be possible otherwise—especially if a common "vocabulary" for the
metadata terms is used
RDFa

4. Add meaning and context
RDFa

5. Add meaning and context
RDFa

6. RDFa

7. Metadata
Increases specificity
Improves common, wide,
unambiguous understanding
Content becomes
computable
RDFa

8. Benefits of having meaningful metadata
Seamless use of data in a web page with
desktop applications
‣ use of microformats tools to generate contact information in a web page
‣ viewing of web page containing microformats using Firefox and Operator
extension: https://addons.mozilla.org/en-US/firefox/addon/4106
‣ transfer of data in the web page to desktop address book
http://microformats.org/code-tools http://en.wikipedia.org/wiki/HCard

12. Metadata evolution on the web
9 2 The World Wide Web—HTML, HTTP, URLs
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13. Metadata evolution on the web
9 2 The World Wide Web—HTML, HTTP, URLs
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14. Metadata evolution on the web
9 2 The World Wide Web—HTML, HTTP, URLs
1 9 Primitive metadata, some semantics about a document L
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15. Metadata evolution on the web
9 2 The World Wide Web—HTML, HTTP, URLs
1 9 Primitive metadata, some semantics about a document L
T M
L H
X M Use of meta tags in head of HTML document
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RDFa

16. Metadata evolution on the web
9 2 The World Wide Web—HTML, HTTP, URLs
1 9 Primitive metadata, some semantics about a document L
T M
L H
X M Use of meta tags in head of HTML document
D
L pt
T M Need for standards and common vocabularies
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RDFa

17. Metadata evolution on the web
9 2 The World Wide Web—HTML, HTTP, URLs
1 9 Primitive metadata, some semantics about a document L
T M
L H
X M Use of meta tags in head of HTML document
D
L pt
T M Need for standards and common vocabularies
cr
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s
X H va
as Early vocabularies J a
em
ch S
S ic
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a nt
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O J
RDFa

18. Metadata evolution on the web
9 2 The World Wide Web—HTML, HTTP, URLs
1 9 Primitive metadata, some semantics about a document L
T M
L H
X M Use of meta tags in head of HTML document
D
L pt
T M Need for standards and common vocabularies
cr
i
s
X H va
as Early vocabularies J a
em
ch Resource Description Framework S
S ic
C S
a nt
m eb
Se w
a x
Q
L
a j
AR
SP
N
W
L
S O
O J
RDFa

19. Metadata evolution on the web
9 2 The World Wide Web—HTML, HTTP, URLs
1 9 Primitive metadata, some semantics about a document L
T M
L H
X M Use of meta tags in head of HTML document
D
L pt
T M Need for standards and common vocabularies
cr
i
s
X H va
as Early vocabularies J a
em
ch Resource Description Framework S
S ic
C S
a nt
m eb RDF files and separate metadata records
Se w
a x
Q
L
a j
AR
SP
N
W
L
S O
O J
RDFa

20. Metadata evolution on the web
9 2 The World Wide Web—HTML, HTTP, URLs
1 9 Primitive metadata, some semantics about a document L
T M
L H
X M Use of meta tags in head of HTML document
D
L pt
T M Need for standards and common vocabularies
cr
i
s
X H va
as Early vocabularies J a
em
ch Resource Description Framework S
S ic
C S
a nt
m eb RDF files and separate metadata records
Se w
a x
Q
L Issues with RDF a j
AR
SP
N
W
L
S O
O J
RDFa

21. Metadata evolution on the web
9 2 The World Wide Web—HTML, HTTP, URLs
1 9 Primitive metadata, some semantics about a document L
T M
L H
X M Use of meta tags in head of HTML document
D
L pt
T M Need for standards and common vocabularies
cr
i
s
X H va
as Early vocabularies J a
em
ch Resource Description Framework S
S ic
C S
a nt
m eb RDF files and separate metadata records
Se w
a x
Q
L Issues with RDF a j
R
S PA
Microformats and similar grassroots driven pragmatic solutions
N
W
L
S O
O J
RDFa

22. Metadata evolution on the web
9 2 The World Wide Web—HTML, HTTP, URLs
1 9 Primitive metadata, some semantics about a document L
T M
L H
X M Use of meta tags in head of HTML document
D
L pt
T M Need for standards and common vocabularies
cr
i
s
X H va
as Early vocabularies J a
em
ch Resource Description Framework S
S ic
C S
a nt
m eb RDF files and separate metadata records
Se w
a x
Q
L Issues with RDF a j
R
S PA
Microformats and similar grassroots driven pragmatic solutions
N
W
L Embedded metadata
S O
O J
RDFa

23. Metadata evolution on the web
9 2 The World Wide Web—HTML, HTTP, URLs
1 9 Primitive metadata, some semantics about a document L
T M
L H
X M Use of meta tags in head of HTML document
D
L pt
T M Need for standards and common vocabularies
cr
i
s
X H va
as Early vocabularies J a
em
ch Resource Description Framework S
S ic
C S
a nt
m eb RDF files and separate metadata records
Se w
a x
Q
L Issues with RDF a j
R
S PA
Microformats and similar grassroots driven pragmatic solutions
N
W
L Embedded metadata
S O
O J
RDFa
RDFa

24. What is RDFa?
RDFa =
Resource Description Framework
in
attributes
http://www.w3.org/TR/rdfa-syntax/ http://www.w3.org/TR/xhtml-rdfa-primer/

25. What is RDFa?
Generic model for the provision of metadata
RDFa =
Resource Description Framework
in
attributes
http://www.w3.org/TR/rdfa-syntax/ http://www.w3.org/TR/xhtml-rdfa-primer/

26. What is RDFa?
Generic model for the provision of metadata
RDFa =
Resource Description Framework
in
attributes
HTML
http://www.w3.org/TR/rdfa-syntax/ http://www.w3.org/TR/xhtml-rdfa-primer/

27. Google webmaster help pages on RDFa
Marking up content using RDFa
RDFa is a way to label content to describe a specific type of
information, such as a restaurant review, an event, a person, or a
product listing. These information types are called entities. Each
entity has a number of properties.
In general, RDFa uses simple attributes in XHTML tags (usually with
<span> or <div>) to assign brief and descriptive names to entities
and properties.
http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=146898

28. Entities
Entities supported by Google
i.e. Google provides a standard set of properties for each of the
following:
‣ person
‣ organisation
‣ event
‣ review
‣ recipe
Each corresponding set of properties, that can be assigned using
RDFa in a web page, is recognised by Google crawler/spider software
and handled in a special way when search results that include the
web page are listed (rich snippets).
The entities and properties are visible to both human readers and
computers!
http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=99170

29. Google’s properties for the “person” entity
http://www.google.com/support/webmasters/bin/answer.py?answer=146646

30. Marking up content with RDFa (extended HTML)
The essence of RDFa...
... is to provide a set of attributes that can be used to carry metadata
in an XML language (hence the 'a' in RDFa). These attributes are:
‣ about—a URI or CURIE specifying the resource the metadata is about
‣ rel and rev—specifying a relationship or reverse-relationship with another
resource
‣ href, src and resource—specifying a related resource
‣ property—specifying a property for the content of an element
‣ content—optional attribute that overrides or supplements the (HTML) content
of the element when using the property attribute
‣ datatype—optional attribute that specifies the datatype of text specified with
the property attribute
‣ typeof—optional attribute that specifies the type(s) of the subject (the
resource that the metadata is about)
http://en.wikipedia.org/wiki/RDFa

31. Thinking it through...
Producing RDFa
‣ identify entities
‣ identify entity properties
‣ identify an appropriate source of entity and property descriptions
(vocabulary, namespace, metadata set, schema, ontology, taxonomy—all
used loosely interchangeably)
‣ markup content using RDFa HTML attributes to provide references to entity
and property types in chosen vocabulary and the corresponding content that
describes each entity instance and property value
‣ ensure nesting of markup implies correct semantic meaning
RDFa

32. Simple RDFa web page
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN"
"http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:v="http://rdf.data-vocabulary.org/#">
<head profile="http://www.w3.org/1999/xhtml/vocab">
<title>Simple RDFa example</title>
</head>
<body>
<div xmlns:v="http://rdf.data-vocabulary.org/#" typeof="v:Person">
My name is <span property="v:name">George Munroe</span>,
also known online as <span property="v:nickname">mungeo</span>.
I am involved in several ventures but my home web site is at:
<a href="http://www.platypusconsultancy.com"
rel="v:url">www.platypusconsultancy.com</a>.
I live in
<span rel="v:address">
<span typeof="v:Address">
<span property="v:locality">Donegal</span>,
<span property="v:region">Ulster</span>
</span>
</span>
and work as a <span property="v:title">consultant trainer</span>
at <span property="v:affiliation">Netskills</span>.
</div>
</body>
</html>
RDFa

33. CSS styles can be added in usual way—use class for <span> blocks...
<!DOCTYPE html>
<html>
<head>
<title>Simple RDFa example</title>
<meta name="description" content="A very simple RDFa web page, using Google webmaster guidelines">
<style type="text/css">
<!--
body {
font: normal 14px Verdana, sans-serif;
background-color: #99ccff;
}
a.url, a.url:visited {
text-decoration: none;
color: #ffffff;
background-color: #000000;
}
a.url:hover {
color: #000000;
background-color: #ffffff;
}
.name {
font-size: 1.5em;
color: #119933;
}
.nickname {
font-size: 1.5em;
color: #993311;
font-style: italic;
}
.address {
font-size: 1.5em;
color: #113399;
}
.title {
font-size: 1.5em;
color: #991199;
}
.affiliation {
font-size: 1.5em;
color: #999911;
}
-->
</style>
</head>
RDFa

34. RDFa markup
Get headings right, XHTML good practice,
RDFa data type dictionary
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN"
"http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head profile="http://www.w3.org/1999/xhtml/vocab">
http://rdfa.info/wiki/How-to-validate

35. RDFa markup
Validate markup using W3C service
http://validator.w3.org/

36. Practical exercise
Creating an HTML page containing RDFa
‣ use Notepad or a similar text editor on your PC to create the sample RDFa
file provided by Google in the webmaster help pages, but including
information about yourself
‣ use the W3C validator to check that all markup in your file is correct
‣ open this file with a web browser on your PC and verify that the information
appears correctly (to human readers)
‣ edit your sample file to add additional properties and entities, select some
additional sample material from the Wikipedia RDFa introduction if you have
sufficient time to experiment
‣ after each edit verify that the markup is valid and that the information
appears correctly when viewed with a web browser

37. RDFa markup
Most common mistakes
Not specifying the XHTML+RDFa DTD
‣ <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN" "http://
www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd">
Forgetting to declare prefix mappings
‣ <div xmlns:v="http://rdf.data-vocabulary.org/#" typeof="v:Person">
The about attribute should resolve to a URL
‣ all RDFa subjects are URLs, absolute or relative
RDFa XHTML markup should be well formed
‣ if a document is not well formed then parsers may have difficulty producing
the correct output
http://rdfa.info/wiki/Common-publishing-mistakes