OpenHPI 6.4 - Linked Data Engineering

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OpenHPI 6.4 - Linked Data Engineering

  1. 1. Semantic Web TechnologiesLecture 6: Applications in the Web of Data 04: Linked Data Engineering Dr. Harald Sack Hasso Plattner Institute for IT Systems Engineering University of Potsdam Spring 2013 This file is licensed under the Creative Commons Attribution-NonCommercial 3.0 (CC BY-NC 3.0)
  2. 2. 2 Lecture 6: Applications in the Web of Data Open HPI - Course: Semantic Web Technologies Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  3. 3. 3 04 - Linked Data EngineeringOpen HPI - Course: Semantic Web Technologies - Lecture 6: Applications in the Web of Data Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  4. 4. How to Get Data From the Web? •Data can only be found on the Web,4 if it is available at some website HTTP HTML JDBC Browser Web-Server Database Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  5. 5. How to Get Data From the Web? •There is a number of different (proprietary) Web APIs, data5 exchange formats, and Mashups on top of that Mashup Web Web Web Web API 1 API 2 API 3 API 4 Database 1 Database 2 Database 3 Database 4 Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  6. 6. In the Web today...6 • Data is locked up in small data islands • Other applications usually cannot access this data... Database Database Database Database Database Database Database Database Database Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  7. 7. How to Get Rid of Closed Data Islands on the Web? •Apply semantic technologies:7 •to publish structured data on the web •to draw connections from one data source to data from other data sources RDF Data RDF Data RDF Data RDF Data RDF Links RDF Links RDF Links Database 1 Database 2 Database 3 Database 4 Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  8. 8. Linked Data Principles8 (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, using the standards (RDF, SPARQL) (4) Include links to other URIs, so that they can discover more things. Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  9. 9. Linked Data Principles (1) Use URIs as names for things.9 • URIs do not only identify documents but also arbitrary objects of the real world as well as abstract concepts http://yovisto.blogspot.com/ http://dbpedia.org/resource/Albert_Einstein http://musicbrainz.org/artist/b10bbbfc-cf9e-42e0-be17-e2c3e1d2600d Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  10. 10. Linked Data Principles10 (2) Use HTTP URIs, so that people can look up those names. • HTTP URIs (URLs) as globally unique names enable dereferencing of assiciated information in the Web • via http Content Negotiation • 303 URIs http Response Code 303 ,See Other‘ (redirect) • Hash URIs http://example.com/Harald#me Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  11. 11. Linked Data for Humans and Computers ■ URI should deliver information as well as for humans as for11 computers, i.e. (Thing) URI Accept: Accept: text/html application/rdf+xml (RDF data) (HTML page) Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  12. 12. Linked Data for Humans and Computers ■ Server delivers different HTTP responses dependent of12 HTTP-Accept-Header (Content Negotiation) http://www4.wiwiss.fu-berlin.de/bizer/pub/LinkedDataTutorial/ Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  13. 13. Linked Data for Humans and Computers ■ URI should deliver information as well as for humans as for13 computers, i.e. (Thing) http://dbpedia.org/resource/Ernest_Hemingway Accept: Accept: text/html application/rdf+xml http://dbpedia.org/data/ http://dbpedia.org/page/ Ernest_Hemingway.rdf Ernest_Hemingway (RDF data) (HTML page) Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  14. 14. Linked Data Principles (3) When someone looks up a URI, provide useful14 information, using the standards (RDF, SPARQL) • RDF as universal data model for publishing structured data on the Web • Make all URIs in the RDF graph dereferencable • Avoid RDF constructs that cause problems in Linked Data context • RDF Reification • RDF Collections und Containers • unnamed Blank Nodes Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  15. 15. Linked Data Principles (4) Include links to other URIs, so that they can15 discover more things. • Link RDF references among data between different data sources, to find information related by content • Relationship Links Links to external LOD Entitites related with the original entity • Identity Links Links to external LOD Entities referring to the same object or concept • Vocabulary Links Links to definitions of the original entity Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  16. 16. The application of the Linked Data Principles leads to a ,Web of Data‘16 Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  17. 17. Development of the ,Web of Data‘17 May 2007 Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  18. 18. Development of the ,Web of Data‘18 Nov 2007 Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  19. 19. Development of the ,Web of Data‘19 Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  20. 20. Development of the ,Web of Data‘20 July 2009 Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  21. 21. Development of the ,Web of Data‘21 September 2010 Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  22. 22. Development of the ,Web of Data‘ 300 Datasets 31B RDF Triples 504M Links22 September 2011 Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  23. 23. Linked Open Data ■ Public Linked Data resources in the Web, licensed as23 „Creative Common CC-BY“ ■ Tim Berners-Lee‘s 5-Star Criteria for Linked Open Data ★ Available on the web (whatever format) but with an open licence, to be Open Data ★ ★ Available as machine-readable structured data (e.g. excel instead of image scan of a table) ★ ★ ★ as (2) plus non-proprietary format (e.g. CSV instead of excel) ★ ★ ★ ★ All the above plus: use open standards from W3C (RDF and SPARQL) to identify things, so that people can point at your stuff ★ ★ ★ ★ ★ All the above, plus: link your data to other people’s data to provide context Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  24. 24. Linked Open Data24 Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  25. 25. Semantic Mashups □ Semantic Mashups are applications that use linked RDF25 data from various data sources. □ in difference to interfaces and exchange formats or ordinary Web APIs, Linked Data offers the following benefits: □ a flexible and standardized data format (RDF) □ standardized access mechanism (http) □ possibility to put links (RDF-Links) among different data sources » enables navigation » is supported by search engines (crawler) » enables expressive search facilities over the crawled data and beyond Vorlesung Semantic Web, Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam
  26. 26. 26 05 - Linked Data Engineering (Part 2) Open HPI - Course: Semantic Web Technologies - Lecture 6: Applications in the Web of Data Semantic Web Technologies , Dr. Harald Sack, Hasso-Plattner-Institut, Universität Potsdam

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