What is RDFa?
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RDFa allows adding metadata to web pages by using attributes in HTML/XHTML tags. It embeds structured metadata directly in web documents rather than keeping metadata separate. Google supports specific entities like people, organizations, events etc. and their properties can be marked up using RDFa to provide rich snippets in search results. RDFa uses attributes like about, rel, property to associate metadata with entities and properties from vocabularies.
What is RDFa?
- 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 1 9 L T M L H X M D L pt T M cr i s X H va as J a em ch 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
- 13. Metadata evolution on the web 9 2 The World Wide Web—HTML, HTTP, URLs 1 9 L T M L H X M D L pt T M cr i s X H va as J a em ch 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
- 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 T M L H X M D L pt T M cr i s X H va as J a em ch 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
- 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 D L pt T M cr i s X H va as J a em ch 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
- 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 cr i s X H va as J a em ch 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
- 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 i s X H va as Early vocabularies J a em ch 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
- 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