WebDB 2010 June 6 th, 2010, Indianapolis, USA. Christian Bizer. Freie Universität Berlin. Christian Bizer: The Web of Linked Data (6/6/2010)

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1 WebDB 2010 June 6 th, 2010, Indianapolis, USA The Web of Linked Data A global public dataspace on the Web Christian Bizer Freie Universität Berlin

2 Outline 1. Foundations of Dataspaces and Linked Data Where do they overlap? 2. The Web of Linked Data What data is out there? 3. Linked Data Applications What is being done with the data? 4. Remarks on Identity Self-descriptive Data Pay-as-you-go Integration

3 The Dataspace Vision Alternative to classic data integration systems in order to cope with growing number of data sources. Properties of dataspaces may contain any kind of data (structured, semi-structured structured, unstructured) require no upfront investment into a global schema provide for data-coexistence give best-effort answers to queries rely on pay-as-you-go as you data integration Franklin, M., Halevy, A., and Maier, D.: From Databases to Dataspaces A new Abstraction for Information Management, SIGMOD Rec

4 Dataspace Architecture Source: Franklin et al: From Databases to Dataspaces, Christian Bizer: The SIGMOD Web of Linked Rec. Data (6/6/2010) 2005.

5 Linked Data Principles Set of best practices for publishing structured data on the Web in accordance with the general architecture of the Web. 1. Use URIs as names for things. 2. Use HTTP URIs so that people can look up those names. 3. When someone looks up a URI, provide useful information. 4. Include statements that link to other URIs so that they can discover related things. Tim Berners-Lee,

6 Architecture of the classic Web Web Browsers Search Engines Single global information space Small set of simple standards d HTTP 1. HTML as document format 2. HTTP URLs as HTML hyperlinks HTML HTML globally unique IDs retrieval mechanism 3. Hyperlinks to connect everything A B C

7 Web 2.0 APIs and Mashups Mashup No single global dataspace Shortcomings 1. APIs have proprietary interfaces Web API Web API Web API Web API 2. Mashups are based on a fixed set of data sources 3. You can not set hyperlinks between data items within different APIs A B C D

8 Web APIs slice the Web into Walled Gardens Image: Bob Jagensdorf, CC-BY

9 Linked Data Extend the Web with a single global dataspace 1. by using to publish structured data on the Web 2. by setting links between data items within different data sources link links links links A B C D E

10 The Data Model pd:cygri rdf:type foaf:person foaf:namef Richard Cyganiak foaf:based_near dbpedia:berlin Flexible graph-based data model.

11 Entities are identified with HTTP URIs pd:cygri rdf:type foaf:person foaf:namef Richard Cyganiak foaf:based_near dbpedia:berlin HTTP URIs take the role of global primary keys. pd:cygri = h i d /f f df# i dbpedia:berlin =

12 Resolving URIs over the Web pd:cygri rdf:type foaf:person foaf:namef Richard Cyganiak foaf:based_near dbpedia:berlin dp:population skos:subject dp:cities_in_germany i The HTTP protocol brings together identification and retrieval again.

13 Following Links deeper into the Web pd:cygri rdf:type foaf:person foaf:namef Richard Cyganiak foaf:based_near dbpedia:berlin dp:population dbpedia:hamburgdi b skos:subject skos:subject dp:cities_in_germany i dbpedia:muenchen skos:subject

14 The Disco Hyperdata Browser

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16 Properties of the Web of Linked Data Global, distributed dataspace built on a simple set of standards, URIs, HTTP Entities are connected by links creating a global data graph that spans data sources and enables the discovery of new data sources. Provides for data-coexistence Everyone can publish data to the Web of Linked Data Everyone can express their personal view on things Everybody can use the schemata that they like for this

17 2. Linked Data Deployment on the Web Is this real? link links links links A B C D E

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

19 LOD Datasets on the Web: May 2007 Over 500 million triples Around 120,000 links between data sources

20 LOD Datasets on the Web: September 2008

21 LOD Datasets on the Web: July 2009 Over 13.1 billion triples Over 142 million links between data sources

22 DBpedia An Interlinking Hub in the Web of Data

23 DBpedia community effort to extract structured information from Wikipedia. provides data about 3.4 million things 312,000 persons 140,000 organizations 413,000 places 94,000 music albums 49,000 films 146,000 species provides identifiers for many common things overlaps with many other data sources on the Web

24 The LOD effort is losing track with the diagram :-)

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27 Uptake in Life Sciences W3C Linking Open Drug Data Effort Bio2 Project Allen Brain Atlas

28 Uptake in the Libraries Community Institutions publishing Linked Data Library of Congress (subject headings) German National Library (PND dataset and subject headings) Swedish National Library (Libris - catalog) Hungarian National Library (OPAC and Digital Library) German Central Library of Economics (subject headings) Workshop: Semantic Web in Bibliotheken (SWIB09) Köln, 24. und 25. November W3C Library Linked Data Incubator Group Open Archives Object Reuse and Exchange (OAI-ORE) Standard

29 Uptake in the Media Industry publish data as /XML and/or embed data into HTML using a

30 The Structural Continuum The Web of Linked Data is interwoven with the classic Web. Unstructured data: HTML Semi-structured data: a embed into HTML Structured data: /XML Services using named entity recognition to annotate texts with Linked Data URIs Open Calais (Thomsons Reuters) for news Zemanta (startup) t for blog posts

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

32 Linked Data Browsers Provide for navigating between data sources in order to explore the dataspace. Tabulator Browser (MIT, USA) Marbles (FU Berlin, DE) OpenLink p Browser (OpenLink, UK) Zitgist Browser (Zitgist, USA) Disco Hyperdata Browser (FU Berlin, DE) Fenfire (DERI, Irland)

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34 DBpedia Mobile Displays DBpedia data on a map Provides for navigating into other data sources

35 Web of Data Search Engines Crawl the dataspace and provide best-effort t query answers over crawled data. Falcons (IWS, China) Sig.ma (DERI, Ireland) Swoogle (UMBC, USA) VisiNav (DERI, Ireland) Watson (Open University, it UK)

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39 What are the big players doing? Yahoo! and Google have started to crawl Linked Data in its a serialization as well as Microformats. Yahoo! provides access to crawled data through the Yahoo BOSS API is using the data within Yahoo Search Monkey to make search results more useful and visually appealing. Google uses crawled data for its Social Graph API uses crawled data to enhance search results snippets for reviews and people.

40 Yahoo! Search Monkey

41 Facebook s Open Graph Protocol Facebook imports a data from external web sites. For instance: IMDb, Microsoft, NHL, Posterous Rotten Tomatoes, TIME, Yelp

42 4. Remarks on 1. Identify 2. Self-descriptive Data 3. Pay-as-you-go Integration

43 Identity Real world objects are identified with multiple URIs. Coupling of identification and retrieval. Data-coexistence: Everybody can say everything about everything. Linked Data website of our research group Wrapper around the DBLP bibliography

44 Identity Resolution Publication of owl:sameas links on the Web. < owl:sameas < Pay-as-you-go as you Identity Management Cheap to set up: Just put a wrapper in front of your DB (for instance using D2R Server) Later: You or somebody else invests effort into identity resolution related approach: itrail hints (Vas Salles et al., VLDB 06, 07) How to create owl:sameas links? Automatic ti based on declarative matching descriptions (for instance using the Silk Linking Framework ) Manually (for instance like within Ueberblick.org)

45 Pay-As-You-Go Data Integration 1. Stage: RAW DATA NOW! don t care too much about the schema just publish your data as on the Web tim_berners_lee_on_the_next_web.html 2. Stage: Increase the usefulness of your data and ease data integration by making it self-descriptive.

46 Enable Clients to retrieve the Schema Clients can resolve the URIs that identify vocabulary terms in order to get their S or OWL definitions. < foaf:name "Richard Cyganiak" ; rdf:type < Some data on the Web Resolve unknown term S or OWL definition < rdf:type owl:class ; rdfs:label "Person"; rdfs:subclassof < ; rdfs:subclassof <

47 Reuse Terms from Common Vocabularies Common Vocabularies Friend-of-a-Friend for describing people and their social network SIOC for describing forums and blogs SKOS for representing topic taxonomies Organization Ontology for describing the structure of organizations GoodRelations for describing products and business entities Music Ontology for describing artists, albums, and performances Review Vocabulary provides terms for representing reviews Common sources of identifiers (URIs) for real world objects LinkedGeoData and Geonames: Locations GeneID and UniProt: Life science identifiers Dbpedia: Wide range of things

48 Publish Schema Mappings on the Web < owl:equivalentclass < Schema Mapping Simple Mappings: OWL owl:equivalentclass, owl:equivalentproperty Complex Mappings: R2R provides value transformation functions structural transformations Pay-as-you-go y Aspect 1. Use a mix of common vocabularies and proprietary terms 2. You or somebody else publishes schema mappings afterwards

49 Somebody-Pays-As-You-Go The overall data integration effort is split between the data publisher, the data consumer and third parties. Data Publisher publishes data as publishes data in a self-descriptive fashion sets links and publishes mappings Fix Overall Data Integration Effort Third Parties set links pointing at your data publish mappings to the Web Publisher s Effort Third Party Effort Data Consumer has to do the rest Consumer s Effort

50 Hands on: How to play around with Linked Data

51 Hands on: How to play around with Linked Data 1. Get some data using a crawler for instance: LDspider (GPL license) 2. Store the data using for instance: Virtuoso (GPL), Sesame (BSD), Jena TDB (BSD) or any relational database or column store you like decision help: Berlin SPARQL Benchmark (Nov 2009) 3. Query and analyze the data using the SPARQL query language SPARQL 1.1 adds support for aggregates, subqueries, negation

52 Shortcut: Billion Triples Challenge Dataset Download the Billion Triples Challenge Dataset 3.2 billion triples (27GB gzipped) crawled from the public Web of Linked Data in March/April If you do something interesting with the data submit your results to the challenge until October 1 st present your results at the 9th International Semantic Web Conference (ISWC2010), November 2010, Shanghai, China

53 Summary Linked Data moves the dataspace vision to a global scale and adds the social/community aspect to it. The Web of Linked Data is growing g rapidly active deployment communities in different domains might have exceeded the critical mass Great playground for experimentation dataspace profiling probabilistic and approximate schema mapping data fusion, data quality, and trust What will the user interfaces look like? Will search engines turn into answer engines?

54 Thanks! References Overview Article Christian Bizer, Tom Heath, Tim Berners-Lee: Linked Data The Story So Far Linking Open Data Project Wiki Tutorial on How to Publish Linked Data on the Web 3 rd Linked Data on the Web Workshop at WWW2010