SKOS, RDFa & Co, Linked Data Related Examples

INFO 4302 - April 20, 2011Bernhard Haslhofer - Cornell University

Today we talk about...

• Simple Knowledge Organization System (SKOS)

• Machine-readable data in (X)HTML(5)(RDFa, Microformats, Microdata)

• Search Engines and machine-readable data

• Facebook Graph API & Open Graph Protocol

Linked Data Recap

Why Linked Data?

• There is lots of information on the Web

• ... valuable information that can be (re-)used

• Problem• information is usually expressed in the form of

HTML documents

• the underlying raw data are locked in closed data silos (mostly DBMS)

Why Linked Data?

• The Web is successful because it provides• Uniform encoding (HTML)

• Uniform addressing (URI)

• Uniform transportation (HTTP)

for the exchange of documents.

• Why not apply the same mechanism to the underlying data?

What is Linked Data?

• A method to build a Web of Data

• Architectural style, set of standards

Web

Publishing Data

• Distinguish between non-information and information resource

• Sample non-information resource• http://dbpedia.org/resource/The_Shining_(film)

• Sample information resource• http://dbpedia.org/page/The_Shining_(film) - HTML

• http://dbpedia.org/data/The_Shining_(film) - RDF

Publishing Data

GET http://dbpedia.org/resource/The_Shining_(film)Accept: application/rdf+xml

303 See OtherLocation: http://dbpedia.org/data/The_Shining_(film)

GET http://dbpedia.org/data/The_Shining_(film)Accept: application/rdf+xml

200 OK...<?xml version="1.0" encoding="utf-8"?><rdf:RDF ...

Simple Knowledge Organization System (SKOS)

• A language for describing controlled vocabularies (taxonomies, thesauri, classification schemes)

http://dbpedia.org/resource/The_Shining_(film)

http://dbpedia.org/resource/Category:1980s_horror_films

http://dbpedia.org/resource/Category:1980s_films

http://www.w3.org/2004/02/skos/core#Concept

skos:subject rdf:type

skos:broader

rdf:type

Excursus: The Semantic Spectrum

semanticexpressiveness

complexity

Glossary

Taxonomy

Thesaurus

Data Model

Ontology

Term/Tag list

SKOSXML/S

Folksonomy

UMLER

OWLDL, FOL, etc

Knowledge Organization Systems (KOS)

Glossary

• A simple (alphabetical) list of terms and their definitions for a particular domain of knowledge

• Useful for creating clear and unambiguous term definitions

Folksonomy

• Collaborative tagging systems

• Web 2.0., social-media, etc...

Controlled Vocabulary

• A simple list of terms, definitions and naming conventions

• Some process “controls” adding and removing term definitions to ensure consistency

• Terms are often defined in relationship to each other

• Taxonomies, Thesauri, and Ontologies are special forms of controlled vocabularies

Taxonomy

• Classification of entities in a hierarchy

• A taxonomy node stands for a real-world entity

animate object

agent

organizationperson

manager employee

subclass of

source: http://upload.wikimedia.org/wikipedia/commons/b/bb/Linnaeus_-_Regnum_Animale_%281735%29.png

Thesaurus

• Associates the meaning of a term with the meaning of another term

• hypernym, hyponym, synonym, antonym

Imagery

Aerial imagery Infrared imagery

Radar imagery

Moving target

indicators

Radar

photography

narrower than

Combat support

equipment

Intelligence and electronic

warfare equipment

Imaging systems

Imaging radarInfrared imaging

systemsrelated to

Ontology

• Defines concepts that represent an area of knowledge

• Machine-read and -interpretable representation

• Classes, instances, relationships, properties, functions, constraints, etc.

http://www.bbc.co.uk/ontologies/programmes/2009-09-07.shtml

Simple Knowledge Organization System (SKOS)

What is SKOS?

• A model for expressing the basic structure and content of concept schemes such as thesauri, classification schemes, taxonomies, folksonomies, and other similar types of controlled vocabularies

• Allows concepts to be composed and published as Linked Data on the Web

• Hides the complexity of OWL - easy to use

semanticexpressiveness

complexity

Glossary

Taxonomy

Thesaurus

Data Model

Ontology

Term/Tag list

SKOSXML/S

Folksonomy

UMLER

OWLDL, FOL, etc

SKOS Concepts are...

• ... identified with URIs

• ... labeled with 1..* natural language strings

• ... documented with various types of notes

• ... semantically linked to each other

• ... aggregated into concept schemes

Example SKOS Concept

skos:Concept

• Concepts are• the units of thought: ideas, meanings, categories of

objects, etc.

• abstract entities which are independent of the terms used to label them

lcsh:sh2007025344#concept

skos:Concept

rdf:type

@prefix skos: <http://www.w3.org/2004/02/skos/core#> .@prefix lcsh: <http://id.loc.gov/authorities/> .

skos:(pref|alt|hidden)Label

• Labels refer to concepts’ natural language(s)• skos:prefLabel: the preferred lexical label

• skos:altLabel: alternative lexical labels (e.g., synonyms)

• skos:hiddenLabel: labels useful for indexing

"Parody films"@en

skos:prefLabel

lcsh:sh2007025344#concept "Movie parodies"@enskos:altLabel

"Send-up films"@en

skos:altLabel

SKOS Semantic Relationships

• The meaning of a concept is also defined by its links to other concepts• skos:broader: hierarchical link to a more general concept

• skos:narrower: hierarchical link to a more specific concept

• skos:related: associative (non-hierarchical) link

"Parody films"@enskos:prefLabellcsh:sh2007025344#concept

"Comedy films"@enskos:prefLabellcsh:sh2007025038#concept

skos:broader

skos:broader

skos:narrower

skos:narrower

SKOS Documentary Notes

• Add further human-readable documentation• skos:scopeNote: info about intended meaning

• skos:definition: complete explanation of meaning

• skos:example: example concept use

“This heading is used as a genre/form heading for films that comically imitate another work or group of works of a more serious nature.”@en

skos:scopeNotelcsh:sh2007025038#concept

"Comedy films"@en

skos:prefLabel

skos:ConceptScheme

• Allow the organization of skos:Concepts in some Knowledge Organization Scheme (KOS)

skos:inScheme

skos:Conceptlcsh:sh2007025038#concept

skos:ConceptSchemelcsh:#genreFormTerms

skos:Concept...

skos:inScheme

Example

• Dereference and analyze“Jack Nicholson” @ New York Times

• http://data.nytimes.com

• http://data.nytimes.com/N5761411277431266513

RDFa, Microformats & Microdata

Why RDFa?

GET http://dbpedia.org/resource/The_Shining_(film)Accept: application/rdf+xml

303 See OtherLocation: http://dbpedia.org/data/The_Shining_(film)

GET http://dbpedia.org/data/The_Shining_(film)Accept: application/rdf+xml

200 OK...<?xml version="1.0" encoding="utf-8"?><rdf:RDF ...

Oh dear!

What is RDFa?

• A mechanism for embedding RDF metadata within XHTML 1.1 Web documents

• Defines a set of attributes to augment visual data with machine-readable hints

• User agents can extract triples from RDFa-enables Web pages

What is RDFa?

• Markup human-readable data (HTML) with machine-readable indicators

...All content on this site is licensed under<a href="http://creativecommons.org/licenses/by/3.0/"> a Creative Commons License</a>.

RDFa Example

...All content on this site is licensed under<a rel=”license” href="http://creativecommons.org/licenses/by/3.0/"> a Creative Commons License</a>.

XHTML

XHTML + RDFa

RDFa Attributes

• about and src: the resource the metadata is about

• rel and rev: (reverse) relationship between resources

• href and resource: the partner resource

• property: a property for the content of an element

• content: override content of an element

• datatype: specify the datatype of text

• typeof: specifies the RDF type(s) or a subject

<div> <h2>The trouble with Bob</h2> <h3>Alice</h3> ...</div>

RDFa Example

<div xmlns:dc="http://purl.org/dc/elements/1.1/"> <h2 property="dc:title">The trouble with Bob</h2> <h3 property="dc:creator">Alice</h3> ...</div>

XHTML

XHTML + RDFa

<div xmlns:dc="http://purl.org/dc/elements/1.1/">! ! ! <div about="/alice/posts/trouble_with_bob"> <h2 property="dc:title">The trouble with Bob</h2> <h3 property="dc:creator">Alice</h3> ... </div>

<div about="/alice/posts/jos_barbecue"> <h2 property="dc:title">Jo's Barbecue</h2> <h3 property="dc:creator">Eve</h3> ... </div>

...

</div>

RDFa Example

XHTML + RDFa

<div typeof="foaf:Person" xmlns:foaf="http://xmlns.com/foaf/0.1/"> <p property="foaf:name"> Alice Birpemswick </p>

<p> Email: <a rel="foaf:mbox" href="mailto:alice@example.com">alice@example.com</a> </p> <p> Phone: <a rel="foaf:phone" href="tel:+1-617-555-7332">+1 617.555.7332</a> </p></div>

RDFa Example

XHTML + RDFa

RDFa Examples

• OReilly.com: http://oreilly.com/catalog/9780596520694/

• Rottentomatoes: http://www.rottentomatoes.com/m/shining/

Microformats

• A Microformat extends conventional HTML tags with semantic information

• Started by Technorati, Inc.; now community-driven (IRC, mailing list, blogs)

• Make use of the following (X)HTML attributes• class

• rel

<div> <div>Joe Doe</div> <div>Jo</div> <div>The Example Company</div> <div>604-555-1234</div> <a href="http://example.com/">http://example.com/</a> </div>

Microformats Example

<head profile="http://www.w3.org/2006/03/hcard"> ... </head> ... <div class="vcard"> <div class="fn">Joe Doe</div> <div class="nickname">Jo</div> <div class="org">The Example Company</div> <div class="tel">604-555-1234</div> <a class="url" href="http://example.com/">http://example.com/</a> </div>

HTML

XHTML + Microformats

Microformats Example

Available Microformats

Microformats vs. RDFa

<div xmlns="http://www.w3.org/1999/xhtml" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns:v="http://www.w3.org/2006/vcard/ns#"> <div about="http://example.com/me/behas" typeof="v:VCard"> <span property="v:fn">Bernhard Haslhofer</span> <span property="v:nickname">behas</span> <div rel="v:adr"> <div typeof="v:Address v:Work"> <span property="v:street-address">301 College Avenue</span> <span property="v:locality">Ithaca</span>, <span property="v:postal-code">14850</span>, <span property="v:country-name">United States</span>. </div> </div> <a rel="v:email" href="mailto:bernhard.haslhofer@cornell.edu">bernhard.haslhofer@cornell.edu</a>. </div></div>

Sample vCard Object in RDFa (see http://www.w3.org/Submission/vcard-rdf/)

Microformats vs. RDFa

<div class="vcard">

<span class="fn">Bernhard Haslhofer</span>

<div class="adr"><div class="street-address">301 College Avenue</div><span class="locality">Ithaca</span><span class="postal-code">14850</span><span class="country-name">United States</span>

</div>

<a class="email" href="mailto:bernhard.haslhofer@cornell.edu">bernhard.haslhofer@cornell.edu</a>

</div>

hCard sample created with http://microformats.org/code/hcard/creator

Also see: http://evan.prodromou.name/RDFa_vs_microformats

Microformats RDFa

flat namespace XML namespaces

support HTML4, XHTML 1.1, and HTML 5 support for XHTML 1.1

use latent HTML attributes introduces new metadata attributes

vocabulary defined by one organization/community open to any RDF-based vocabulary

Microdata (HTML5)

• A very young HTML 5 proposition that extends Microformats and addresses its shortcomings

• Items are created within an itemscope

• Ever item is assigned an arbitrary number of properties (itemprop)

• Uses global identifiers for typing and naming items

Microdata Example

<div itemscope itemtype="http://data-vocabulary.org/Person">

<span itemprop="name">Bernhard Haslhofer</span>, <span itemprop="nickname">behas</span>.

<div itemprop="address" itemscope itemtype="http://data-vocabulary.org/Address"><span itemprop="street-address">301 College Avenue</span><span itemprop="locality">Ithaca</span><span itemprop="country-name">United States</span>

</div>

</div>

Search engines and machine-readable data

Google Rich Snippets

• Reviews

• People

• Products

• Businesses and organizations

• Recipes

• Events

Google Rich Snippets

<div>L’Amourita PizzaReviewed by Ulysses Grant on Jan 6.Delicious, tasty pizza on Eastlake!L'Amourita serves up traditional wood-fired Neapolitan-style pizza, brought to your table promptly and without fuss. An ideal neighborhood pizza joint.Rating: 4.5</div>

HTML

Google Rich Snippets

<div> <div itemscope itemtype="http://data-vocabulary.org/Review"> <span itemprop="itemreviewed">L’Amourita Pizza</span> Reviewed by <span itemprop="reviewer">Ulysses Grant</span> on <time itemprop="dtreviewed" datetime="2009-01-06">Jan 6</time>. <span itemprop="summary">Delicious, tasty pizza in Eastlake!</span> <span itemprop="description">L'Amourita serves up traditional wood-fired Neapolitan-style pizza, brought to your table promptly and without fuss. An ideal neighborhood pizza joint.</span> Rating: <span itemprop="rating">4.5</span> </div></div>

Microdata

Google Rich Snippets

<div class="hreview"> <span class="item"> <span class="fn">L’Amourita Pizza</span> </span> Reviewed by <span class="reviewer">Ulysses Grant</span> on <span class="dtreviewed"> Jan 6<span class="value-title" title="2009-01-06"></span> </span>. <span class="summary">Delicious, tasty pizza on Eastlake!</span> <span class="description">L'Amourita serves up traditional wood-fired Neapolitan-style pizza, brought to your table promptly and without fuss. An ideal neighborhood pizza joint.</span> Rating: <span class="rating">4.5</span></div>

Microformats

Google Rich Snippets

<div xmlns:v="http://rdf.data-vocabulary.org/#" typeof="v:Review"> <span property="v:itemreviewed">L’Amourita Pizza</span> Reviewed by <span property="v:reviewer">Ulysses Grant</span> on <span property="v:dtreviewed" content="2009-01-06">Jan 6</span>. <span property="v:summary">Delicious, tasty pizza on Eastlake!</span> <span property="v:description">L'Amourita serves up traditional wood-fired Neapolitan-style pizza, brought to your table promptly and without fuss. An ideal neighborhood pizza joint.</span> Rating: <span property="v:rating">4.5</span></div>

RDFa

Facebook Graph API & Open Graph Protocol

Readings

Required Reading

• SKOS Primer: http://www.w3.org/TR/skos-primer/

• RDFa Primer: Bridging the Human and Data Webs.http://www.w3.org/TR/xhtml-rdfa-primer/

• HTML Microdata: http://www.w3.org/TR/microdata/

• Microformats: http://microformats.org/

Recommended Readings

• SKOS Vocabularies Overview:

• RDFa.info: http://rdfa.info/wiki/RDFa_Wiki

• CC REL: Creative Commons Rights Expression Language (CC REL)

source: http://upload.wikimedia.org/wikipedia/commons/a/a7/Wollmilchsau.png

~2000 2011

Reality

Dream

HTML 5Microdata

RDFa