"RDFa - what, why and how?" by Mike Hewett and Shamod Lacoul

Mike Hewett ([email protected])

Shamod Lacoul ([email protected])

Members of the League of Extraordinary Modelers (LEM)

Silicon Valley CodeCamp 2010

October 9, 2010

What, Why and How

Licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License

The Speakers

Mike Hewett has 25 years of experience in building AI systems, focusing on constructing knowledge bases and reasoning about knowledge. He is the author of the Algernon rule engine and the Jatha LISP library. Mike has a Masters in AI from Stanford University and a PhD in Computer Science from the University of Texas at Austin.

Shamod Lacoul is a software entrepreneur, developer and consultant. He has been working as a software consultant for 7 years, focusing on back-end and data integration technologies. He is an assistant organizer of the Silicon Valley Semantic Technologies (SVST) Meetup. He has a Masters in Software Engineering and Bachelors in Computer Science from San Jose State University.

Outline

A quick overview of RDFa and a scenario setup

What is RDFa? Why use RDFa? How to use RDFa? How is RDFa related to Semantic Web? Current websites using RDFa

Overview of RDFa

RDFa adds semantics to web page content.

Semantics == Meaning

However, RDFa can be added to any XML-like

structured content.

What is Semantics?

What does this sentence mean?

“The Bears are in New York”

1. Bears are migrating to New York state.

2. Bears are migrating to New York City.

3. Chicago is playing the Giants in football.

4. Prices are lower on the NY Stock Exchange.

5. Is it the title of a book?

Scenario: Lou’s Café hours

Scraping information from web pages.

Can a program find out when Lou’s Café is open on Saturday?

Scenario: Lou’s Café hours

When is Lou’s Café open on Saturday? The hours are hard to find by eye. Even harder to find with a program.

But… The hours could be annotated with RDFa tags. Programs can easily find the information. Easier than scraping the web page and

guessing.

Scraping information from the web

People often use programs to scrape information from web pages

Database

Web Server

Web Page

Program

CopyFindExtractUse

Scraping information is easier:

RDFa makes it easier to find and retrieve information from web pages

Database

Web Server

Web Page

Program

CopyFindExtractUse

The vision of the Semantic Web

Agents access information in DBs directly.

RDFDatabase

Web Server

Web Page

Program

QueryUse

What is RDF?

RDF is a data model where all data consists of 3-tuples of entities, commonly called triples.

<subject> <predicate> <object>

<x:Person-9372> <x:firstName> “Don”

<x:Person-9372> <x:lastName> “Knuth”

<x:Person-9372> <x:friendOf> <x:Person-8614>

Outline

A quick overview of RDFa and a scenario setup What is RDFa? Why use RDFa? How to use RDFa? How is RDFa related to Semantic Web? Current websites using RDFa

What is RDFa?

RDFa defines attributes for words or phrases that should be treated as semantic entities.

<div xmlns:v=“http://rdf.data-vocabulary.org/#”

typeof="v:Person">



Albuquerque

NM



</div>

RDFa is a W3C recommendation

RDFa example – metadata

<div about="/id/rdfa-course">

<h3 property="dc:title">RDFa Course</h3>



This course covers the basics of RDFa...



Last modified:



6th Feb 2009



</div>

Borrowed from a talk by Jeni Tennison at the XML Summer School

subject predicate objectabout

src

propertyrelrevtypeof

contenthrefresourcedatatype

about=”rdfa-course"

property="dc:title"

RDFa Course

The attributes map to RDF components

RDFa attributes

<div about=”rdfa-course"> <h3 property="dc:title">RDFa Course</h3>

RDFa vocabulary

Provides the keywords and the semantics Often called a microformat Examples of vocabularies:

DC = Dublin Core Describes document metadata dc:title dc:author

FOAF = Friend of a Friend foaf:name foaf:mbox

Other useful vocabularies

hReview (recognized by Google): itemreviewed, rating, reviewer, dtreviewed, description, summary

hCard (Person) (rec. by Google): name, nickname, photo, title, role, url, affiliation, address, …

hCalendar (Event) (rec. by Google): summary, url, location, description, startDate, endDate, duration, eventType, geo, photo

Facebook Share & Yahoo SearchMonkey RDFa (video) (rec. by Google): image_src, video_src, description, title, video_width, video_height, …

RDFa example – person

<div xmlns:v="http://rdf.data-vocabulary.org/#" typeof="v:Person">

My name is Bob Smith, but people call me Smithy.

Here is my homepage: <a href="http://www.example.com" rel="v:url">www.example.com</a>.

I live in 

Albuquerque, NM 

and work as an engineer

at ACME Corp.

My friends: <a href="http://darryl-blog.example.com" rel="v:friend">Darryl</a>, <a href="http://edna-blog.example.com" rel="v:friend">Edna</a>

</div>

RDFa example – event

<div xmlns:v="http://rdf.data-vocabulary.org/#" typeof="v:Event">

<a href="http://www.example.com/events/spinaltap" rel="v:url" property="v:summary">Spinal Tap</a>

<img src="spinal_tap.jpg" rel="v:photo" />

After their highly-publicized search for a new drummer, Spinal Tap kicks off their latest comeback tour with a San Francisco show. 

When: Oct 15, 7:00PM—

9:00PM

Where: 

Warfield Theatre,





982 Market St,

San Francisco,

CA 

…

Category: Concert </div>

Alternatives for adding Semantics

RDFa – W3C standard + validator Microformat syntax Microdata syntax Proprietary tags and syntax

Facebook: Open Graph

Microformat example – event

<div class="location vcard">

Warfield Theatre,



982 Market St ,

San Francisco,

CA 



</div>

Microdata example - event



Warfield Theatre 

982 Market St, San Francisco, CA







Outline


Why use RDFa?

Embed semantics in XHTML

Re-use attributes

The HTML and the RDF can exist in the same document

For Search Engine Optimization (SEO)

Open Graph

<html xmlns="http://www.w3.org/1999/xhtml"

xmlns:og=http://opengraphprotocol.org/schema/

xmlns:fb="http://www.facebook.com/2008/fbml">

<head> <title>The Rock (1996)</title>

<meta property="og:title" content="The Rock"/>

<meta property="og:type" content="movie"/>

<meta property="og:url"

content="http://www.imdb.com/title/tt0117500/"/>

<meta property="og:image"

content="http://ia.media-imdb.com/rock.jpg"/>

<meta property="og:site_name" content="IMDb"/>

<meta property="og:description" content="A group of U.S. Marines, under command of a renegade general, take over Alcatraz and threaten San Francisco Bay with biological weapons."/>

... </head> ... </html>

How

Better understanding of the content Better ad placement To build Rich Snippets:

Uses RDFa

Outline


A sample webpage without RDFa

A sample webpage with RDFa

Can you tell the difference?

NO, it’s tough with your naked eye.

Reasons:

RDFa attributes are meant for machines.

RDFa attributes are embedded inside HTML tags invisible to the user.

One quick way to find RDFa tags is by using a tool called RDFaDev

RDFaDev is a Firefox plugin

enables you to examine the RDFa markup

allows you to query the data on the page using SPARQL

detects common pitfalls in the use of RDFa

http://rdfadev.sourceforge.net/

http://rdfadev.sourceforge.net/

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Silicon Valley Code Camp</title></head><body> Weekend at the Silicon Valley Code Camp 2010 Starts on: 10-09-2010 Ends on: 10-10-2010 See <a href="http://siliconvalley-codecamp.com/">Silicon Valley Code Camp 2010</a>This event is located at Foothills College </body></html>

HTML without RDFa

http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd



<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" xmlns:cal="http://www.w3.org/2002/12/cal/icaltzd#" xmlns:xs="http://www.w3.org/2001/XMLSchema#"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Insert title here</title></head><body> Weekend at the Silicon Valley Code Camp 2010Starts on: 10-09-2010Ends on: 10-10-2010See <a rel="cal:url" href="http://siliconvalley-codecamp.com/">Silicon Valley Code Camp 2010</a> This event is located at Foothills College</body></html>

HTML with RDFa

http://check.rdfa.info/

Use to validate RDFa



Result from http://check.rdfa.info/

NOTE: It also tells you how Facebook, Google parses your RDFa


GRDDL = Gleaning Resource Descriptions from Dialects of Languages

a technique of extracting RDF data from XML documents (in particular XHTML pages).

Source: http://www.w3.org/TR/2006/WD-grddl-primer-20061002/

<?xml version="1.0" encoding="UTF-8"?> <html xmlns="http://www.w3.org/1999/xhtml" xml:base="http://www.dc4plus.com/references/rdf_sem.html" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:foaf="http://xmlns.com/foaf/0.1/" ><head profile="http://ns.inria.fr/grddl/rdfa/"> <title>Biblio description</title> </head> <body> <h1>Biblio description</h1> <dl about="http://www.w3.org/TR/2004/REC-rdf-mt-20040210/"> <dt>Title</dt> <dd property="dc:title">RDF Semantics - W3C Recommendation 10 February 2004</dd> <dt>Author</dt> <dd rel="dc:creator" href="#a1"> <link rel="rdf:type" href="[foaf:Person]" /> Patrick Hayes see <a rel="foaf:homepage" href="http://www.ihmc.us/users/user.php?UserID=42">homepage</a> </dd></dl></body></html>

An example of RDFa with GRDDL profile

Source: http://www-sop.inria.fr/acacia/personnel/Fabien.Gandon/tmp/grddl/rdfaprimer/PrimerRDFaSection.html

An output of GRDDL service is RDF

Source: http://www-sop.inria.fr/acacia/personnel/Fabien.Gandon/tmp/grddl/rdfaprimer/PrimerRDFaSection.html

A visual graph of an RDF

Outline


How is RDFa related to the Semantic Web

as a whole?

Source: http://www.flickr.com/photos/ldodds/4043803502/

Linked Data

Source: http://www.semanticfocus.com/blog/entry/title/introduction-to-the-semantic-web-vision-and-technologies-part-2-foundations/

Semantic Web stack

Web Ontology Language (OWL)

- additional vocabulary along with a formal semantics

- an extension to RDF and RDF-Schema (RDF-S)

Triple Store (A database for RDF)

Source: http://test.ical.ly/tags/phpunit/

SPARQL – a query language for RDF

- a glue to connect, query and reconstructdisparate sources of RDF data

- similar to SQL for RDF

Outline


Examples of websites

currently using

RDFa

Summary

RDFa provides semantic tags that are embedded in web pages

RDFa helps software to understand the content of web pages

Useful RDFa tools are RDFaDev, checkrdfa.info, GRDDL Service, HTML editor, etc.

RDFa is a stepping stone to full Semantic Web capability BBC, BestBuy, O’Reilly are the early-adopters.

Links to related information

http://www.w3.org/TR/rdfa-core/ http://en.wikipedia.org/wiki/Rdfa http://www.google.com/webmasters/tools/richsnippets http://developers.facebook.com/docs/opengraph http://semantic-drupal.com/ http://xmlsummerschool.com/curriculum-2010/semantic-t

echnologies-2010/ http://www.jenitennison.com/talks/xmlss2010/RDFa.pdf http://opengraphprotocol.org/

http://www.w3.org/TR/rdfa-core/

http://en.wikipedia.org/wiki/Rdfa

http://www.google.com/webmasters/tools/richsnippets

http://developers.facebook.com/docs/opengraph

http://semantic-drupal.com/

http://xmlsummerschool.com/curriculum-2010/semantic-technologies-2010/

http://xmlsummerschool.com/curriculum-2010/semantic-technologies-2010/

http://www.jenitennison.com/talks/xmlss2010/RDFa.pdf

http://opengraphprotocol.org/

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"RDFa - what, why and how?" by Mike Hewett and Shamod Lacoul

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