Linked Data

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Information about Linked Data
Technology

Published on March 2, 2009

Author: danja

Source: slideshare.net

Description

presented at Practical Semantic Astronomy 2009

Linking Open Data Danny Ayers SemAst2009

Danny Ayers

SemAst2009

Obligatory Children Slide

Credits: Many slides derived from those of Tom Heath, Michael Hausenblas, Chris Bizer, Richard Cyganiak, Olaf Hartig

Many slides derived from those of

Tom Heath, Michael Hausenblas, Chris Bizer, Richard Cyganiak, Olaf Hartig

Quote Linked Data is the Semantic Web done right, and the Web done right.” - Tim Berners-Lee

Linked Data is the Semantic Web done right, and the Web done right.”

- Tim Berners-Lee

Introduce the concept of Linked Data Highlight why you would want to publish Linked Data on the Web Introduce the principles and best practices of publishing Linked Data on the Web Demonstrate the creation and consumption of Linked Data Answer your burning Linked Data publishing questions Objectives

Introduce the concept of Linked Data

Highlight why you would want to publish Linked Data on the Web

Introduce the principles and best practices of publishing Linked Data on the Web

Demonstrate the creation and consumption of Linked Data

Answer your burning Linked Data publishing questions

Overview From a Web of Documents to a Web of Data Web APIs, Microformats, and Linked Data Linked Data Deployment on the Web What data is out there? Applications What is being done with the data?

From a Web of Documents to a Web of Data

Web APIs, Microformats, and Linked Data

Linked Data Deployment on the Web

What data is out there?

Applications

What is being done with the data?

Classic Data : in silos Image: Bob Jagensdorf, http://flickr.com/photos/darwinbell/, CC-BY

The Classic Web Single global information space URLs as globally unique IDs retrieval mechanism HTML as shared content format Hyperlinks Shortcomings Content is not well structured You can not ask expressive queries You can not process content within applications B C HTML HTML HTML Web Browsers Search Engines hyper- links A

Single global information space

URLs as

globally unique IDs

retrieval mechanism

HTML as shared content format

Hyperlinks

Shortcomings

Content is not well structured

You can not ask expressive queries

You can not process content within applications

What do we actually want? Use the Web like a single global database.

Solution Web APIs Microformats Linked Data Publish structured data directly on the Web Different Approaches

Web APIs

Microformats

Linked Data

Web APIs

Mashups Positive APIs expose structured data APIs enable new applications Negative Usually proprietary interfaces Mashups are based only on fixed set of sources You can't usually set hyperlinks between data objects Mashup Up Web API A Web API B Web API C Web API D

Positive

APIs expose structured data

APIs enable new applications

Negative

Usually proprietary interfaces

Mashups are based only on fixed set of sources

You can't usually set hyperlinks between data objects

Web APIs slice the Web into separate data silos Image: Bob Jagensdorf, http://flickr.com/photos/darwinbell/, CC-BY

What do we want? Use the Web as a single global database using what we know works on the Web

Connecting Worlds One Web! Data Documents

What works on the Web? Uniform Identifiers (URIs) Common Interface Protocol (HTTP) Standard Representation Formats (HTML, Atom/RSS etc)

Uniform Identifiers (URIs)

Common Interface Protocol (HTTP)

Standard Representation Formats (HTML, Atom/RSS etc)

What works on the Web? The Hyperlink

The Hyperlink

Evolving the Link <a href=” http://example.org/home.html “> Home Page </a> page.html home.html

<a href=” http://example.org/home.html “>

Home Page

</a>

Evolving the Link <a href=”http://example.org/home.html” rel=”home”> Home Page </a> page.html home.html home

<a href=”http://example.org/home.html”

rel=”home”>

Home Page

</a>

Microformats Embed structured data into HTML pages. hCard, hCalender, hReview, XFN, … Compatible with the idea of the Web as single information space. Shortcomings Only a fixed set of microformats exist No direct way to connect data items <div class=&quot;vevent&quot;> <span class=&quot;summary&quot;>bdigital</span> <abbr class=&quot;dtstart&quot; title=&quot;2008-05-20&quot;>May 20</abbr> - <abbr class=&quot;dtend&quot; title=&quot;2007-05-22&quot;>22</abbr> </div>

Embed structured data into HTML pages.

hCard, hCalender, hReview, XFN, …

Compatible with the idea of the Web as single information space.

Shortcomings

Only a fixed set of microformats exist

No direct way to connect data items

Evolving the Link <rdf:Description rdf:about=” http://example.org/page ”> <x:home rdf:resource=” http://example.org/home ” /> </rdf:Description> page home x:home

<rdf:Description

rdf:about=” http://example.org/page ”>

<x:home

rdf:resource=” http://example.org/home ” />

</rdf:Description>

Linked Data B C Thing typed links A D E typed links typed links typed links Thing Thing Thing Thing Thing Thing Thing Thing Thing Use Semantic Web technologies to publish structured data on the Web, set links between data from one data source to data within other data sources .

Use Semantic Web technologies to

publish structured data on the Web,

set links between data from one data source to data within other data sources .

RDF Relations <rdf:Description rdf:about=” http://example.org/page ”> <x:home rdf:resource=” http://example.org/home ” /> </rdf:Description> x:home subject object http://example.org /page ... http://example.org /home ...

<rdf:Description

rdf:about=” http://example.org/page ”>

<x:home

rdf:resource=” http://example.org/home ” />

</rdf:Description>

Identifiers Identification by Description Non-HTTP URIs HTTP URIs

Identification by Description

Non-HTTP URIs

HTTP URIs

Linked Data Principles Use URIs as names for things Use HTTP URIs so that people can look up those names. When someone looks up a URI, provide useful information. Include links to other URIs. so that they can discover more things. Tim Berners-Lee 2007 http://www.w3.org/DesignIssues/LinkedData.html

Use URIs as names for things

Use HTTP URIs so that people can look up those names.

When someone looks up a URI, provide useful information.

Include links to other URIs. so that they can discover more things.

Tim Berners-Lee 2007

http://www.w3.org/DesignIssues/LinkedData.html

The RDF Data Model Richard Cyganiak dbpedia:Berlin foaf:name foaf:based_near foaf:Person rdf:type pd:cygri

Data objects are identified with HTTP URIs pd:cygri Richard Cyganiak dbpedia:Berlin foaf:name foaf:based_near foaf:Person rdf:type pd:cygri = http://richard.cyganiak.de/foaf.rdf#cygri dbpedia:Berlin = http://dbpedia.org/resource/Berlin

Follow Your Nose... Richard Cyganiak dbpedia:Berlin foaf:name foaf:based_near foaf:Person rdf:type pd:cygri dp:Cities_in_Germany 3.405.259 dp:population skos:subject

Dereferencing URIs over the Web Richard Cyganiak dbpedia:Berlin foaf:name foaf:based_near foaf:Person rdf:type dbpedia:Hamburg dbpedia:Muenchen skos:subject skos:subject pd:cygri dp:Cities_in_Germany 3.405.259 dp:population skos:subject

Universal Connector <resourceB> rdfs:seeAlso <resourceA>

Universal Connector <resourceB> rdfs:seeAlso <resourceA> foaf:Person rdf:type

Take Care! <resourceB> owl:sameAs <resourceA>

The Disco – Hyperdata Browser

 

Semantic Web Specifications HTTP + URIs RDF + RDFs OWL SKOS SPARQL RDFa GRDDL Turtle/N3 Coming soon: POWDER, OWL2, RIF

HTTP + URIs

RDF + RDFs

OWL

SKOS

SPARQL

RDFa

GRDDL

Turtle/N3

What of Web Services? “ Web APIs Are Just Web Sites” - Paul Downey Linked Data is exposed as (very simple) RESTful services

What of RDF Stores? A triplestore is just a cache of a chunk of the Semantic Web Convenient for data merging, querying (SPARQL) and inference See also: Semantic Web Client Library

What of the Real World? source: http://danbri.org/words/2008/04/15/300 based on timbl 1994

W3C Linking Open Data Project Community effort to publish existing open license datasets as Linked Data on the Web interlink things between different data sources

Community effort to

publish existing open license datasets as Linked Data on the Web

interlink things between different data sources

LOD Datasets on the Web: May 2007

LOD Datasets on the Web: August 2007

LOD Datasets on the Web: February 2008

LOD Datasets on the Web: September 2008

LOD Datasets on the Web: March 2009

Spotlight: Geonames over 8 million geographical locations feature hierarchy

over 8 million geographical locations

feature hierarchy

Spotlight: DBpedia extracts structured data from Wikipedia. covers over 2.2 million concepts from various domains.

extracts structured data from Wikipedia.

covers over 2.2 million concepts from various domains.

Example RDF Links RDF links from DBpedia to other data sources RDF link from a FOAF profile to DBpedia <http://dbpedia.org/resource/Berlin> owl:sameAs <http://sws.geonames.org/2950159> . <http://richard.cyganiak.de/foaf.rdf#cygri> foaf:topic_interest <http://dbpedia.org/resource/Semantic_Web> . <http://dbpedia.org/resource/Tim_Berners-Lee> owl:sameAs <http://www4.wiwiss.fu-berlin.de/dblp/resource/person/100007> .

RDF links from DBpedia to other data sources

RDF link from a FOAF profile to DBpedia

Universities and Research Institutes Massachusetts Institute of Technology (USA) University of Southampton (UK) Freie Universität Berlin (DE) DERI (IRE) KMi, Open University (UK) University of London (UK) Universität Hannover (DE) University of Pennsylvania (USA) Universität Leipzig (DE) Universität Karlsruhe (DE) Joanneum (AT) University of Toronto (CA) Organizations publishing Linked Data Companies BBC (UK) OpenLink (UK) Zitgist (USA) Talis (UK) Garlik (UK) Mondeca (FR) Cyc Foundation (USA)

Universities and Research Institutes

Massachusetts Institute of Technology (USA)

University of Southampton (UK)

Freie Universität Berlin (DE)

DERI (IRE)

KMi, Open University (UK)

University of London (UK)

Universität Hannover (DE)

University of Pennsylvania (USA)

Universität Leipzig (DE)

Universität Karlsruhe (DE)

Joanneum (AT)

University of Toronto (CA)

Companies

BBC (UK)

OpenLink (UK)

Zitgist (USA)

Talis (UK)

Garlik (UK)

Mondeca (FR)

Cyc Foundation (USA)

Applications B C Thing typed links A D E typed links typed links typed links Thing Thing Thing Thing Thing Thing Thing Thing Thing Search Engines Linked Data Mashups Linked Data Browsers What can I do with this?

What can I do with this?

Linked Data Browsers Tabulator Browser (MIT, USA) Marbles (FU Berlin, DE) OpenLink RDF Browser (OpenLink, UK) Zitgist RDF Browser (Zitgist, USA) Disco Hyperdata Browser (FU Berlin, DE) Fenfire (DERI, Irland)

Tabulator Browser (MIT, USA)

Marbles (FU Berlin, DE)

OpenLink RDF Browser (OpenLink, UK)

Zitgist RDF Browser (Zitgist, USA)

Disco Hyperdata Browser (FU Berlin, DE)

Fenfire (DERI, Irland)

Tabulator

Linked Data Mashups Domain-specific applications - using Linked Data from the Web

Domain-specific applications

- using Linked Data from the Web

DBpedia Mobile Geospatial entry point into the Web of Data Starts with DBpedia, Revyu and Flickr data

Geospatial entry point into the Web of Data

Starts with DBpedia, Revyu and Flickr data

Web of Data Search Engines Falcons (IWS, China) Sindice (DERI, Ireland) MicroSearch (Yahoo, Spain) Watson (Open University, UK) SWSE (DERI, Ireland) Swoogle (UMBC, USA)

Falcons (IWS, China)

Sindice (DERI, Ireland)

MicroSearch (Yahoo, Spain)

Watson (Open University, UK)

SWSE (DERI, Ireland)

Swoogle (UMBC, USA)

Falcons

Why publish Linked Data on the Web? Your data becomes part of a single global data space (the Web of Data = Semantic Web) People can use various data browsers to explore your data Your data is crawled by Semantic Web search engines and can be used by independent applications People start setting links to your data, which allows more people to find and use your data

Your data becomes part of a single global data space (the Web of Data = Semantic Web)

People can use various data browsers to explore your data

Your data is crawled by Semantic Web search engines and can be used by independent applications

People start setting links to your data, which allows more people to find and use your data

Why publish Linked Data on the Web? Linked Data builds on the classic architecture of the Web Linked Data is more generic then Web APIs or Microformats Builds on standards in contrast to proprietary Web APIs Enables applications that work against an unbound set of data sources and incorporate new data sources as they become available on the Web

Linked Data builds on the classic architecture of the Web

Linked Data is more generic then Web APIs or Microformats

Builds on standards in contrast to proprietary Web APIs

Enables applications that work against an unbound set of data sources and incorporate new data sources as they become available on the Web

Linked Data Principles Use URIs as names for things Use HTTP URIs so that people can look up those names. When someone looks up a URI, provide useful information. Include links to other URIs. so that they can discover more things. Tim Berners-Lee 2007 http://www.w3.org/DesignIssues/LinkedData.html

Use URIs as names for things

Use HTTP URIs so that people can look up those names.

When someone looks up a URI, provide useful information.

Include links to other URIs. so that they can discover more things.

Tim Berners-Lee 2007

http://www.w3.org/DesignIssues/LinkedData.html

Example : Source Data

Example : First Pass @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . @prefix owl: <http://www.w3.org/2002/07/owl#> . @prefix x: <http://purl.org/stuff/astro#> . x:Megrez rdf:type x:A3_dwarf ; x:magnitude &quot;3.1&quot; ; x:partOf [ rdf:type x:Constellation ; x:hasName &quot;Ursa Major&quot; ] . (RDF Turtle/N3 Syntax)

Example : Vocabulary @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . @prefix x: <http://purl.org/stuff/astro#> . x:Star rdf:type rdfs:Class . x:Constellation rdf:type rdfs:Class . x:A3_Dwarf rdfs:subClassOf x:Star . x:magnitude rdf:type rdf:Property . x:partOf rdf:type rdf:Property . x:hasName rdf:type rdf:Property .

But... Use URIs as names for things Use HTTP URIs so that people can look up those names. When someone looks up a URI, provide useful information. Include links to other URIs. so that they can discover more things. Existing vocabularies and resource URIs are likely to be well-linked already – reuse is good!

Use URIs as names for things

Use HTTP URIs so that people can look up those names.

When someone looks up a URI, provide useful information.

Include links to other URIs. so that they can discover more things.

Example : Better Linkage @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . @prefix x: <http://purl.org/stuff/astro#> . @prefix astro: <http://archive.astro.umd.edu/ont/astronomy.owl#> . @prefix foaf: <http://xmlns.com/foaf/0.1/> . @prefix dolce: <http://www.loa-cnr.it/ontologies/DOLCE-Lite.owl#> . @prefix dbpedia: <http://dbpedia.org/resource/> . dbpedia:Delta_Ursae_Majoris rdf:type x:A3_Dwarf ; foaf:name &quot;Megrez&quot;; x:magnitude &quot;3.1&quot; ; dolce:part-of dbpedia:Ursa_Major ; rdfs:seeAlso <http://www.dcs.gla.ac.uk/workshops/semast09> . dbpedia:Ursa_Major rdf:type astro:Constellation .

Mass-Publication Techniques Generally either: bulk conversion live mapping from existing databases

Generally either:

bulk conversion

live mapping from existing databases

New Vocabularies : voiD Vocabulary of Interlinked Datasets Classes: Dataset | Linkset | TechnicalFeature | Properties: statItem | feature | subset | target | sparqlEndpoint | linkPredicate | exampleResource | vocabulary | subjectsTarget | objectsTarget | dataDump | uriLookupEndpoint | uriRegexPattern |

New Vocabularies : Scovo Statistical Core Vocabulary

&quot;It is important to look as it as an interconnection bus, and it hasn't started working in earnest until one person's data is being used by some other unplanned use. This unexpected reuse is the measure.&quot; - Tim Berners-Lee, re. State of the Semantic Web Finishing Quotes

&quot;Engineer for serendipity.&quot; - Roy T. Fielding, re. REST Finishing Quotes

http://hyperdata.org/astronomy/ Related Links etc.

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