An introduction to Linked Open Data

An introduction to Linked Open Data
An Introduction to Linked (Open) Data Ali Khalili, PhD Knowledge Representation & Reasoning Group VU University Amsterdam 09-10 April 2018 SIKS-course Utrecht
Why do we need the Data Web? Linked Open Data 2Ali Khalili Linked Open Data
Why do we need the Data Web? Linked Open Data 2Ali Khalili Linked Open Data Problem: Try to search for these things on the current Web: • Apartments near Dutch-English bilingual childcare in Utrecht
Why do we need the Data Web? Linked Open Data 2Ali Khalili Linked Open Data Problem: Try to search for these things on the current Web: • Apartments near Dutch-English bilingual childcare in Utrecht Web Server funda.nl kindergarden.nl Has data about childcares in Utrecht. Knows about real estate offers in the Netherlands. DBDB HTMLHTML Web Server
Why do we need the Data Web? Linked Open Data 2Ali Khalili Linked Open Data Problem: Try to search for these things on the current Web: • Apartments near Dutch-English bilingual childcare in Utrecht Web Server funda.nl kindergarden.nl Has data about childcares in Utrecht. Knows about real estate offers in the Netherlands. DBDB HTMLHTML Web Server RDF
Why do we need the Data Web? (con.) Linked Open Data 3Ali Khalili 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 3Ali Khalili 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.
Big Data Linked Open Data 4Ali Khalili Linked Open Data
Big Data Linked Open Data 4Ali Khalili Linked Open Data
Big Data: Characteristics Linked Open Data 5Ali Khalili Linked Open Data
Big Data: Characteristics Linked Open Data 6Ali Khalili Linked Open Data
Big Data: Characteristics Linked Open Data 6Ali Khalili Data Web Linked Open Data
Evolution of the Web Linked Open Data 7Ali Khalili Linked Open Data https://mcgratha.wordpress.com/
Evolution of the Web Linked Open Data 7Ali Khalili Linked Open Data https://mcgratha.wordpress.com/ 1998: Semantic Web Road map
Evolution of the Web Linked Open Data 7Ali Khalili Linked Open Data https://mcgratha.wordpress.com/ 1998: Semantic Web Road map 2006: emergence of Data Web
How to build the Data Web?
Linked Data Linked Open Data 9Ali Khalili Linked Open Data • A set of best practices for publishing data on the Web.
Linked Data Linked Open Data 9Ali Khalili 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 10Ali Khalili Linked Open Data WWW World
5 Open Data Linked Open Data 11Ali Khalili 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/
5 Open Data Linked Open Data 12Ali Khalili Linked Open Data
Linked Open Data Cloud Linked Open Data 13Ali Khalili Linked Open Data http://lod-cloud.net/
Linked Open Data Cloud Linked Open Data 14Ali Khalili Linked Open Data http://lod-cloud.net/ Last updated: 2017-08-22
Statistics Linked Open Data 15Ali Khalili Linked Open Data http://lodlaundromat.org/ http://stats.lod2.eu/ more than 3426 datasets
Linked Open Data 16Ali Khalili Linked Open Data How to deliver Linked Data to people?
Linked Open Data 17Ali Khalili Linked Open Data Interlinking Enrichment Quality Analysis Evolution Exploration Extraction Storage/ Querying Authoring Linked (Open) Data Lifecycle http://stack.linkeddata.org/
Linked Open Data 18Ali Khalili Linked Open Data Lifecycle Exploration
Linked Open Data 18Ali Khalili Linked Open Data Lifecycle • Search • Browse • Visualize Exploration
Search for Linked Data Linked Open Data 19Ali Khalili Linked Open Data Lifecycle Exploration
Search for Linked Data Linked Open Data 19Ali Khalili Linked Open Data Lifecycle Exploration http://swoogle.umbc.edu/
Search for Linked Data Linked Open Data 20Ali Khalili Linked Open Data Lifecycle Exploration
Search in Linked Data Linked Open Data 21Ali Khalili Linked Open Data Lifecycle Exploration http://www.wolframalpha.com/ Question Answering Systems
Search for Linked Data Vocabularies Linked Open Data 22Ali Khalili Linked Open Data Lifecycle Exploration http://lov.okfn.org/
Search for/in Linked Data Linked Open Data 23Ali Khalili Linked Open Data Lifecycle Exploration http://lotus.lodlaundromat.org
Hands-on: Dereference some URIs using Postman Linked Open Data Lifecycle Exploration #1 text/turtle text/n3 application/rdf+xml application/ld+json application/json RDF mime types
Search for Linked Data Linked Open Data 25Ali Khalili Linked Open Data Lifecycle Data hub http://datahub.io search for data, register published datasets, create and manage groups of datasets… Exploration
Search for/in Linked Data Linked Open Data 26Ali Khalili Linked Open Data Lifecycle Exploration
Search for/in Linked Data Linked Open Data 26Ali Khalili Linked Open Data Lifecycle Exploration
Search for/in Linked Data Linked Open Data 27Ali Khalili Linked Open Data Lifecycle Exploration https://www.google.com/cse/
Search for/in Linked Data Linked Open Data 28Ali Khalili Linked Open Data Lifecycle Exploration http://schema.org/ http://bl.ocks.org/danbri/1c121ea8bd2189cf411c
Browsing/Inspecting Linked Data Linked Open Data 29Ali Khalili Linked Open Data Lifecycle Loupe http://loupe.linkeddata.es/ discovering the type of data contained in a dataset, its structure, and the vocabularies used… Exploration
Browsing Linked Data - Serendipity Linked Open Data 30Ali Khalili Linked Open Data Lifecycle Linked Data Reactor http://ld-r.org Exploration Khalili, P. van Andel, P. van den Besselaar, and K. A. de Graaf, “Fostering serendipitous knowledge discovery using an adaptive multigraph-based faceted browser,” in The ninth international conference on knowledge capture: k-cap 2017 Universities participatedIn locatedIn foundationYear Projects Locations years type OrgTypes subType OrgSubTypes funding Funding Programs name names country Countries partnerWith Organizations type label labels years closureYear name names published Publications title year years titles ranking Rankings international Collaboration rankings administrative boundary Admin Boundaries code polygon codes polygons Resource Object Value Property Dataset
Browsing Linked Data Linked Open Data 31Ali Khalili Linked Open Data Lifecycle Exhibit http://www.simile-widgets.org/exhibit3/ Exploration
Visualizing Linked Data Linked Open Data 32Ali Khalili Linked Open Data Lifecycle Exploration Using existing visualisations for structured data e.g. Sgvizler http://dev.data2000.no/sgvizler/
Visualizing Linked Data Linked Open Data 33Ali Khalili Linked Open Data Lifecycle Exploration Using graph-based visualizations e.g. RelFinder http://www.visualdataweb.org/relfinder/relfinder.php
Extraction Linked Open Data 34Ali Khalili Linked Open Data Lifecycle
from Unstructured sources Linked Open Data 35Ali Khalili 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
from Unstructured sources Linked Open Data 35Ali Khalili 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
from Unstructured sources Linked Open Data 35Ali Khalili 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
Named Entity Recognition Linked Open Data 36Ali Khalili Linked Open Data Lifecycle Extraction http://spotlight.dbpedia.org http://bioportal.bioontology.org/annotator
Example Applications of NER Linked Open Data 37Ali Khalili Linked Open Data Lifecycle Contextual recommendations/visualizations e.g. Zemanta https://wordpress.org/plugins/zemanta Extraction
Hands-on: Named Entity Recognition using DBpedia Spotlight Linked Open Data Lifecycle Extraction http://demo.dbpedia-spotlight.org http://demo.ld-r.org/twitterAnalysis #2
Linked Open Data 39Ali Khalili Linked Open Data Lifecycle Extraction http://nlp2rdf.org Interoperability between NLP tools, language resources and annotations NLP Interchange Format (NIF) Named Entity Recognition & Disambiguation (NERD) http://nerd.eurecom.fr/
from Semi-structured sources Linked Open Data 40Ali Khalili Linked Open Data Lifecycle Extraction
from Semi-structured sources Linked Open Data 40Ali Khalili Linked Open Data Lifecycle Extraction 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-domain 1,445,000 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 41Ali Khalili Linked Open Data Lifecycle Extraction DBpedia
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-domain 1,445,000 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 41Ali Khalili Linked Open Data Lifecycle Extraction DBpedia
Linked Open Data 42Ali Khalili Linked Open Data Lifecycle Extraction • Ad-hoc • DBpedia extraction framework • Generic • OpenRefine (Spreadsheets to RDF) from Semi-structured sources
Linked Open Data 43Ali Khalili Linked Open Data Lifecycle Extraction Hands-on: OpenRefine http://openrefine.risis.eculture.labs.vu.nl https://goo.gl/bPZFxr Download the following CSV file: Convert it to RDF using OpenRefine: #3
from Structured sources Linked Open Data 44Ali Khalili Linked Open Data Lifecycle Extraction
from Structured sources Linked Open Data 44Ali Khalili Linked Open Data Lifecycle Extraction Triplification by Materialization
from Structured sources Linked Open Data 45Ali Khalili Linked Open Data Lifecycle Extraction Triplification by SPARQL-to-SQL-Rewriting
Triplification Linked Open Data 46Ali Khalili Linked Open Data Lifecycle Extraction • Relational Database to RDF R2RML: RDB to RDF Mapping Language http://www.w3.org/TR/r2rml/ • D2R Server: Accessing databases with SPARQL & as Linked Data http://d2rq.org/ • Sparqlify defining RDF views on relational databases http://sparqlify.org/
Storage & Querying Linked Open Data 47Ali Khalili Linked Open Data Lifecycle
Relational Databases vs. Triple Stores Linked Open Data 48Ali Khalili Linked Open Data Lifecycle Storage/Querying • A relational databases’ (e.g. MySQL, PostgreSQL, Oracle) natural representation is a collection of interlinked tables. • A triple stores’ (e.g. OpenSesame, Virtuoso, Stardog) natural representation is a multi-relational network, or graph.
Relational Databases vs. Triple Stores Linked Open Data 49Ali Khalili Linked Open Data Lifecycle Storage/Querying • 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 Linked Open Data 50Ali Khalili Linked Open Data Lifecycle Storage/Querying • Native triple stores 4Store, AllegroGraph, BigData, Jena TDB, Sesame, Stardog, OWLIM and uRiKa • RDBMS-backed triple stores Jena SDB, IBM DB2 and Virtuoso • NoSQL triplestores CumulusRDF • Graph databases with RDF extensions Neo4J, MarkLogic http://www.dataversity.net/introduction-to-triplestores/
index-free adjacency Labeled Property Graphs (LPGs) vs RDF Linked Open Data 51Ali Khalili Linked Open Data Lifecycle Storage/Querying https://neo4j.com/blog/rdf-triple-store-vs-labeled-property-graph-difference/
index-free adjacency Labeled Property Graphs (LPGs) vs RDF Linked Open Data 51Ali Khalili Linked Open Data Lifecycle Storage/Querying https://neo4j.com/blog/rdf-triple-store-vs-labeled-property-graph-difference/
HDT - Your binary format for RDF Linked Open Data 52Ali Khalili Linked Open Data Lifecycle Storage/Querying • HDT (Header, Dictionary, Triples) • a compact data structure and binary serialization format for RDF • keeps big datasets compressed to save space while maintaining search and browse operations without prior decompression. • Linked Data Fragments • Streaming approach • Query the web of data on Web-scale http://www.rdfhdt.org http://linkeddatafragments.org/
SPARQL – SQL for the Linked Data Linked Open Data 53Ali Khalili Linked Open Data Lifecycle Storage/Querying What can be done with SPARQL that can't be done with SQL?
SPARQL – SQL for the Linked Data Linked Open Data 53Ali Khalili Linked Open Data Lifecycle Storage/Querying 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 – SQL for the Linked Data Linked Open Data 53Ali Khalili Linked Open Data Lifecycle Storage/Querying 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 – SQL for the Linked Data Linked Open Data 54Ali Khalili Linked Open Data Lifecycle Storage/Querying • SPARQL allows the conceptual data model to be fully explored through queries.
SPARQL – SQL for the Linked Data Linked Open Data 54Ali Khalili Linked Open Data Lifecycle Storage/Querying • 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
SPARQL – SQL for the Linked Data Linked Open Data 55Ali Khalili Linked Open Data Lifecycle Storage/Querying • Queries that have to traverse a chain of connections are particularly complex in SQL while very simple in SPARQL.
SPARQL – SQL for the Linked Data Linked Open Data 55Ali Khalili Linked Open Data Lifecycle Storage/Querying • Queries that have to traverse a chain of connections are particularly complex in SQL while very simple in SPARQL.
SPARQL – SQL for the Linked Data Linked Open Data 56Ali Khalili Linked Open Data Lifecycle Storage/Querying • 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 Linked Open Data 57Ali Khalili Linked Open Data Lifecycle Storage/Querying http://yasgui.org/
WYSIWYQ — What You See Is What You Query 58Ali Khalili, Albert Meroño-Peñuela UI Query WYSIWYQ – What You See Is What You Query Linked Open Data Lifecycle Storage/Querying
WYSIWYQ — What You See Is What You Query 58Ali Khalili, Albert Meroño-Peñuela UI Query ? But, how about turning a query into an interactive UI? WYSIWYQ – What You See Is What You Query Linked Open Data Lifecycle Storage/Querying
Hands-on Linked Open Data 59Ali Khalili Linked Open Data Lifecycle Storage/Querying Write a SPARQL query to return a list of all educational institutes in the Netherlands. DBpedia Endpoints: http://dbpedia.org/sparql http://live.dbpedia.org/sparql http://dbpedia-live.openlinksw.com/sparql http://lod.openlinksw.com/sparql http://fragments.dbpedia.org/ DBpedia – Linked Data Fragments #4
Authoring Linked Open Data 60Ali Khalili Linked Open Data Lifecycle
Semantic Wikis Linked Open Data 61Ali Khalili 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
OntoWiki use case: Catalogus Professorum Linked Open Data 62Ali Khalili Linked Open Data Lifecycle Authoring Semantic Data Wiki The Catalogus Professorum Lipsiensis – Semantics-based Collaboration and Exploration for Historians
OntoWiki use case: Catalogus Professorum Linked Open Data 62Ali Khalili Linked Open Data Lifecycle Authoring Semantic Data Wiki The Catalogus Professorum Lipsiensis – Semantics-based Collaboration and Exploration for Historians
Semantic Content Annotation Linked Open Data 63Ali Khalili Linked Open Data Lifecycle Authoring WYSIWY - What You See Is What You GetG
Semantic Content Annotation Linked Open Data 63Ali Khalili Linked Open Data Lifecycle Authoring WYSIWY - What You See Is What You GetG
Semantic Content Annotation Linked Open Data 63Ali Khalili Linked Open Data Lifecycle Authoring WYSIWY - What You See Is What You Mean http://rdface.aksw.org M
LD-R Framework Linked Open Data 64Ali Khalili Linked Open Data Lifecycle Authoring http://ld-r.org
Interlinking Linked Open Data 65Ali Khalili Linked Open Data Lifecycle
Interlinking Linked Open Data 66Ali Khalili Linked Open Data Lifecycle • 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
Interlinking Methods Linked Open Data 67Ali Khalili Linked Open Data Lifecycle • 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 Linked Open Data 68Ali Khalili Linked Open Data Lifecycle http://silk-framework.com/ Interlinking Semi-automatic
LIMES Framework Linked Open Data 69Ali Khalili Linked Open Data Lifecycle http://aksw.org/Projects/LIMES Interlinking Semi-automatic
Lenticular Lenses Linked Open Data 70Ali Khalili Linked Open Data Lifecycle http://lenticular-lens.sms.risis.eu Interlinking Semi-automatic A. K. Idrissou, R. Hoekstra, F. van Harmelen, A. Khalili, and P. van den Besselaar, “Is my:sameAs the same as your:samAas?,” in The ninth international conference on knowledge capture: k-cap 2017
Enrichment Linked Open Data 71Ali Khalili Linked Open Data Lifecycle
ORE (Ontology Repair and Enrichment) Linked Open Data 72Ali Khalili Linked Open Data Lifecycle Enrichment http://ore.aksw.org/
Quality Analysis Linked Open Data 73Ali Khalili Linked Open Data Lifecycle
Linked Data Quality Dimensions Linked Open Data 74Ali Khalili Linked Open Data Lifecycle Quality Assessment for Linked Data: A Survey
Luzzu Linked Open Data 75Ali Khalili Linked Open Data Lifecycle http://eis.iai.uni-bonn.de/Projects/Luzzu Quality Analysis Tools
RDFUnit Linked Open Data 76Ali Khalili Linked Open Data Lifecycle http://aksw.org/Projects/RDFUnit Quality Analysis Tools
Evolution Linked Open Data 77Ali Khalili Linked Open Data Lifecycle
EvoPat – Pattern based KB Evolution Linked Open Data 78Ali Khalili 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
Linked Open Data 79Ali Khalili Linked Open Data Interlinking Enrichment Quality Analysis Evolution Exploration Extraction Storage/ Querying Authoring Linked (Open) Data Lifecycle http://stack.linkeddata.org/ Life Cycle Conclusion
Linked Open Data 80Ali Khalili Linked Open Data Conclusion
Linked Open Data 80Ali Khalili Linked Open Data Conclusion
References Linked Open Data 81Ali Khalili 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/

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