an introduction to linked (open) data

An Introduction to

Linked (Open) Data

Ali Khalili, PhDKnowledge Representation & Reasoning Group

VU University Amsterdam

http://www.ali1k.com

Why do we need the Data Web?

Linked Open Data 2Ali Khalili

Linked Open Data



Linked Open Data

Problem: Try to search for these things on the current Web:

• Apartments near Dutch-English bilingual childcare in Amsterdam



Linked Open Data



Web Server

funda.nl kindergarden.nl

Has data about childcare in Amsterdam.

Knows about real estate offers in the

Netherlands.

DBDB

HTMLHTML

Web Server

http://funda.nl

http://kindergarden.nl



Linked Open Data



Web Server

funda.nl kindergarden.nl

Has data about childcare in Amsterdam.

Knows about real estate offers in the

Netherlands.

DBDB

HTMLHTML

Web Server

RDF

http://funda.nl

http://kindergarden.nl

Why do we need the Data Web? (con.)


Linked Open Data

• Researchers working on Semantic Web topics in the Middle East. • Side effects of some drugs with a specific chemical compound

prescribed for certain diseases. • Who are mayors of central European towns elevated more than 1000m? • Which movies are starring both Brad Pitt and Angelina Jolie? • All soccer players, who played as goalkeeper for a club that has a

stadium with more than 40.000 seats and who are born in a country with more than 10 million inhabitants

• …

Why do we need the Data Web? (con.)


Linked Open Data

• Researchers working on Semantic Web topics in the Middle East. • Side effects of some drugs with a specific chemical compound

prescribed for certain diseases. • Who are mayors of central European towns elevated more than 1000m? • Which movies are starring both Brad Pitt and Angelina Jolie? • All soccer players, who played as goalkeeper for a club that has a

stadium with more than 40.000 seats and who are born in a country with more than 10 million inhabitants

• …

Information is available on the Web, but opaque to current search.

Evolution of the Web


Linked Open Data

https://mcgratha.wordpress.com/




Linked Open Data


1998: Semantic Web Road map


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



Linked Open Data


1998: Semantic Web Road map

2006: emergence of Data Web


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

Linked Data


Linked Open Data

• A set of best practices for publishing data on the Web.

Linked Data


Linked Open Data

• A set of best practices for publishing data on the Web.• Follows 4 simple principles:

1. Use URIs as names (identifiers) for conceptual things.

2. Use HTTP URIs so that users can look up (dereference) those names.

3. When someone looks up a URI, provide useful information, using the open standards such as RDF, SPARQL, etc.

4. Include links to other URIs, so that users can discover more things.

Linked Data Principles


Linked Open Data

WWW World

5 Open Data


Linked Open Data

make your stuff available on the Web (whatever format) under an open license

make it available as structured data (e.g., Excel instead of image scan of a table)

make it available in a non-proprietary open format (e.g., CSV as well as of Excel)

use Linked Data format (URIs to identify things, RDF to represent data)

link your data to other people’s data to provide context

http://5stardata.info/

http://5stardata.info/

5 Open Data


Linked Open Data

Linked Open Data Cloud


Linked Open Data

http://lod-cloud.net/


Linked Open Data Cloud


Linked Open Data



Statistics


Linked Open Data

http://lodlaundromat.org/

http://stats.lod2.eu/

more than 3426 datasets

http://lodlaundromat.org/

http://stats.lod2.eu/


Linked Open Data

Hands-on


Linked Open Data

Ranking of universities Amount of funding acquired by universities?

Hands-on


Linked Open Data

Ranking of universities Amount of funding acquired by universities?

Hands-on

Make a sorted list of all universities in the Netherlands displaying their recent rankings (e.g. CWTS Leiden Ranking or Times World University Rankings) together with the amount of

EC contributions on H2020 projects?


Linked Open Data

Interlinking

Enrichment

Quality Analysis

Evolution

Exploration

Extraction

Storage/Querying

Authoring

Linked (Open) Data Lifecycle

http://stack.linkeddata.org/



Linked Open Data Lifecycle

Exploration



• Search • Browse • Visualize

Exploration

Search for Linked Data


Linked Open Data Lifecycle Exploration




http://swoogle.umbc.edu/

http://swoogle.umbc.edu/

Search in Linked Data



http://www.wolframalpha.com/

Question Answering Systems

http://www.wolframalpha.com




http://lov.okfn.org/

http://www.apple.com




http://lotus.lodlaundromat.org

http://lotus.lodlaundromat.org/




http://demo.ld-r.org/lotus





Data hub http://datahub.io search for data, register published datasets, create and manage groups of datasets…

Exploration

http://datahub.io/

Search for/in Linked Data






https://www.google.com/cse/





http://schema.org/

http://bl.ocks.org/danbri/1c121ea8bd2189cf411c

http://schema.org


Browsing Linked Data



Loupe http://loupe.linkeddata.es/ discovering the type of data contained in a dataset, its structure, and the vocabularies used…

Exploration

http://loupe.linkeddata.es/




Linked Data Reactor http://ld-r.org a component-based framework to view, browse and edit Linked Data

Exploration

http://ld-r.org




Exhibit http://www.simile-widgets.org/exhibit/

Exploration

http://www.simile-widgets.org/exhibit/

Visualizing Linked Data



Using existing visualisations for structured datae.g. Sgvizler http://dev.data2000.no/sgvizler/

http://dev.data2000.no/sgvizler/




Using graph-based visualizationse.g. RelFinder http://www.visualdataweb.org/relfinder/relfinder.php

http://www.visualdataweb.org/relfinder/relfinder.php

Hands-on



1. List of all universities in the Netherlands 2. University Rankings (e.g. CWTS Leiden Ranking or Times

World University Rankings) 3. H2020 EU projects repository

Explore Web of Data for the following data sources:

https://en.wikipedia.org/wiki/List_of_universities_in_the_Netherlands







http://www.leidenranking.com/downloads







https://www.timeshighereducation.com/world-university-rankings/2016/world-ranking#!/page/0/length/25







https://open-data.europa.eu/en/data/dataset/cordis-h2020projects-under-horizon-2020-2014-2020







Extraction



from Unstructured sources


Linked Open Data Lifecycle Extraction

…After leaving Apple, Jobs took a few of its members with him to found NeXT, a computer platform development company based in Redwood City, specializing in state-of-the-art computers for higher-education and business markets. In addition, Jobs helped to initiate the development of the visual effects industry when he funded the spinout of the computer graphics division of George Lucas's company Lucasfilm in 1986. The new company, Pixar, would eventually produce the first fully computer-animated film, Toy Story…

NLP, Text mining, Annotation






Named Entity Recognition







foundedBy

Relation Extraction




http://spotlight.dbpedia.org

http://bioportal.bioontology.org/annotator

http://spotlight.dbpedia.org

http://bioportal.bioontology.org/annotator





Contextual visualizationse.g. Zemanta https://wordpress.org/plugins/zemanta

https://wordpress.org/plugins/zemanta



http://nlp2rdf.org

Interoperability between NLP tools, language resources and annotations

NLP Interchange Format (NIF)

Named Entity Recognition & Disambiguation (NERD) http://nerd.eurecom.fr/

http://nlp2rdf.org


from Semi-structured sources






Resource Property Value

Multi-lingual• 38.3m things in 125 languages • 23.8m are localized descriptions of things in the English DBpedia • English DBpedia describes 4.58m things (68,091,260 statements)

Multi-domain1,445,000 persons, 735,000 places (including 478,000 populated places), 411,000 creative works (including 123,000 music albums, 87,000 films and 19,000 video games), 241,000 organizations (including 58,000 companies and 49,000 educational institutions), 251,000 species and 6,000 diseases


Linked Open Data Lifecycle Extraction DBpedia



• Ad-hoc• DBpedia extraction framework

• Generic• OpenRefine


https://github.com/dbpedia/extraction-framework

http://openrefine.org/

from Structured sources






Triplification by Materialization




Triplification by SPARQL-to-SQL-Rewriting

Triplification



• Relational Database to RDFR2RML: RDB to RDF Mapping Languagehttp://www.w3.org/TR/r2rml/

• D2R Server: Accessing databases with SPARQL & as Linked Datahttp://d2rq.org/

• Sparqlifydefining RDF views on relational databaseshttp://sparqlify.org/

http://www.w3.org/TR/r2rml/

http://d2rq.org/

http://sparqlify.org/

Hands-on



1. University Rankings (e.g. CWTS Leiden Ranking or Times World University Rankings)

2. H2020 EU projects repository

Triplify the following data sources:

http://openrefine.org/

Storage & Querying



Relational Databases vs. Triple Stores


Linked Open Data Lifecycle Storage/Querying

• A relational databases’ (e.g. MySQL, PostgreSQL, Oracle) natural representation is a collection interlinked tables.

• A triple stores’ (e.g. OpenSesame, AllegroGraph, Neo4j) natural representation is a multi-relational network, or graph.

Relational Databases vs. Triple Stores



• Relational databases tend to not maintain public access points (some might provide Web APIs).

• Triple stores maintain public access points called SPARQL end-points.

• Relational database users tend to not publish their schemas.

• Triple store users tend to reuse and extend public schemas called ontologies.

Existing Triple Stores



• Native triple stores4Store, AllegroGraph, BigData, Jena TDB, Sesame, Stardog, OWLIM and uRiKa

• RDBMS-backed triple storesJena SDB, IBM DB2 and OpenLink Virtuoso

• NoSQL triplestoresCumulusRDF

SPARQL – SQL for the Linked Data



What can be done with SPARQL that can't be done with SQL?




What can be done with SPARQL that can't be done with SQL?

• SPARQL queries are considerably better aligned with users’ mental models of a domain.




• SPARQL allows the conceptual data model to be fully explored through queries.




• SPARQL allows the conceptual data model to be fully explored through queries.

- example:workPhone rdfs:subPropertyOf example:phone- example:cellPhone rdfs:subPropertyOf example:phone- example:homePhone rdfs:subPropertyOf example:phone




• Queries that have to traverse a chain of connections are particularly complex in SQL while very simple in SPARQL.




• In addition to SELECT, INSERT and DELETE, SPARQL supports ASK queries.

• SPARQL includes syntax (i.e. SERVICE) to call two or more data sources within a single query.

• …

SPARQL Query Interface



http://yasgui.org/

http://yasgui.org/

Hands-on



Write a SPARQL query to return a list of all universities in the Netherlands sorted by name.

DBpedia Endpoints: http://dbpedia.org/sparql http://live.dbpedia.org/sparql http://dbpedia-live.openlinksw.com/sparql http://lod.openlinksw.com/sparql

http://dbpedia.org/sparql

http://live.dbpedia.org/sparql

http://dbpedia-live.openlinksw.com/sparql

http://lod.openlinksw.com/sparql

Authoring



Semantic Wikis


Linked Open Data Lifecycle Authoring

• Semantic (Text) Wikis Authoring of semantically annotated text

• Semantic Data Wikis Direct authoring of structured information (i.e. RDF, RDF-Schema, OWL)

http://semantic-mediawiki.org/

http://aksw.org/Projects/OntoWiki

http://semantic-mediawiki.org/

http://aksw.org/Projects/OntoWiki

OntoWiki use case: Catalogus Professorum


Linked Open Data Lifecycle Authoring Semantic Data Wiki

The Catalogus Professorum Lipsiensis – Semantics-based Collaboration and Exploration for Historians

http://ceur-ws.org/Vol-658/paper532.pdf

Semantic Content Annotation



WYSIWY - What You See Is What You GetG

Semantic Content Annotation



WYSIWY - What You See Is What You Mean

http://rdface.aksw.org

M

http://rdface.aksw.org

LD-R Framework



http://ld-r.org

http://ld-r.org

Interlinking



Interlinking



• The degree to which entities that represent the same concepts are linked to each other.

• “Connecting things that are somehow related” • Methods

• Automatic, Semi-automatic, Manual • Universal, Domain-specific

<http://dbpedia.org/resource/VU_University_Amsterdam>

<https://www.wikidata.org/entity/Q1065414>

SameAs

http://dbpedia.org/resource/VU_University_Amsterdam

https://www.wikidata.org/entity/Q1065414

Interlinking Methods



• Ontology Matching • establish links between ontologies underlying two

data sources.

• Instance Matching (Link Discovery) • discover links between instances contained in two

data sources.

SILK Framework



http://silk-framework.com/

Interlinking Semi-automatic


LIMES Framework



http://aksw.org/Projects/LIMES

Interlinking Semi-automatic

http://aksw.org/Projects/LIMES


Hands-on


Linked Open Data Lifecycle Interlinking

1. Universities in CWTS Leiden Ranking or Times World University Rankings

2. Universities in H2020 EU projects

Reconcile the following resources against DBpedia:

Enrichment



ORE (Ontology Repair and Enrichment)


Linked Open Data Lifecycle Enrichment

http://ore.aksw.org/

http://ore.aksw.org/

Quality Analysis



Linked Data Quality Dimensions



Quality Assessment for Linked Data: A Survey

http://www.semantic-web-journal.net/system/files/swj773.pdf

Luzzu



http://eis.iai.uni-bonn.de/Projects/Luzzu

Quality Analysis Tools

http://eis.iai.uni-bonn.de/Projects/Luzzu

RDFUnit



http://aksw.org/Projects/RDFUnit

Quality Analysis Tools

http://aksw.org/Projects/RDFUnit

Evolution



EvoPat – Pattern based KB Evolution


Linked Open Data Lifecycle Evolution

• Inspired by Software Refactoring • Agile Knowledge Engineering • Basic & compound evolution patterns

http://link.springer.com/chapter/10.1007%2F978-3-642-17746-0_41

http://link.springer.com/chapter/10.1007%2F978-3-642-17746-0_41


Linked Open Data

Interlinking

Enrichment

Quality Analysis

Evolution

Exploration

Extraction

Storage/Querying

Authoring

Linked (Open) Data Lifecycle


Life Cycle


Hands-on Result


Linked Open Data


Linked Open Data

References


Linked Open Data

• http://slidewiki.org/deck/11936_semantic-data-web-lecture-series • Introduction to linked data and its lifecycle on the web • http://euclid-project.eu/ • http://videolectures.net/wims2011_auer_interlinked/ • https://vimeo.com/76257120 • http://www.slideshare.net/slidarko/evolving-the-web-into-a-giant-global-

database-3880018 • http://www.dataversity.net/introduction-to-triplestores/ • http://www.topquadrant.com/2014/05/05/comparing-sparql-with-sql/

http://slidewiki.org/deck/11936_semantic-data-web-lecture-series

http://dl.acm.org/citation.cfm?id=2529646

http://euclid-project.eu/

http://videolectures.net/wims2011_auer_interlinked/

https://vimeo.com/76257120

http://www.slideshare.net/slidarko/evolving-the-web-into-a-giant-global-database-3880018

http://www.dataversity.net/introduction-to-triplestores/

http://www.topquadrant.com/2014/05/05/comparing-sparql-with-sql/

an introduction to linked (open) data

Data & Analytics