Tutorial "Linked Data Query Processing" Part 1 "Introduction" (WWW 2013 Ed.)

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These are the slides from my WWW 2013 Tutorial "Linked Data Query Processing" http://db.uwaterloo.ca/LDQTut2013/

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Tutorial "Linked Data Query Processing" Part 1 "Introduction" (WWW 2013 Ed.)

  1. 1. Linked Data Query ProcessingTutorial at the 22nd International World Wide Web Conference (WWW 2013)May 14, 2013http://db.uwaterloo.ca/LDQTut2013/Olaf HartigUniversity of Waterloo
  2. 2. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 2Tutorial Outline(1) Introduction(2) Theoretical Foundations(3) Source Selection Strategies(4) Execution Process(5) Query Planning and Optimization
  3. 3. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 3Linked Data Query ProcessingTutorial at the 22nd International World Wide Web Conference (WWW 2013)May 14, 2013http://db.uwaterloo.ca/LDQTut2013/1. IntroductionOlaf HartigUniversity of Waterloo
  4. 4. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 4Outline The Linked Data Principles Paradigms for Querying Linked Data Characteristics of the “Database System”
  5. 5. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 5The Traditional, Hypertext WebMovieDBData exposedto the Webvia HTMLCIA WorldFactbook
  6. 6. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 6Towards a Web of Linked DataMovieDB:( Albania , unemployment rate , 13.2% ):Data model: RDF( War Child , release date , 12 July 1999 )( War Child , filming location , Albania )( Michael Davie , directed , War Child ):CIA WorldFactbook
  7. 7. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 7Towards a Web of Linked DataMovieDB( http://...imdb.../WarChild , release date , 12 July 1999 )( http://...imdb.../WarChild , filming location , http://cia.../Albania )( http://...imdb.../MichaelDavie , directed , http://...imdb.../WarChild ):( http://cia.../Albania ,unemployment rate , 13.2% ):Data model: RDFGlobal identifier: URICIA WorldFactbook
  8. 8. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 8Towards a Web of Linked DataMovieDB( http://cia.../Albania ,unemployment rate , 13.2% ):Data model: RDFGlobal identifier: URIAccess mechanism: HTTP( http://...imdb.../WarChild , release date , 12 July 1999 )( http://...imdb.../WarChild , filming location , http://cia.../Albania )( http://...imdb.../MichaelDavie , directed , http://...imdb.../WarChild ):CIA WorldFactbook
  9. 9. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 9Towards a Web of Linked DataMovieDBCIA WorldFactbook( http://...imdb.../WarChild , release date , 12 July 1999 )( http://...imdb.../WarChild , filming location , http://cia.../Albania )( http://...imdb.../MichaelDavie , directed , http://...imdb.../WarChild ):( http://cia.../Albania ,unemployment rate , 13.2% ):Data model: RDFGlobal identifier: URIAccess mechanism: HTTPConnection: data links
  10. 10. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 10Supplementary Access Methods● RDF dump: the whole dataset provided as a big file● SPARQL endpoint: Web service that allows for executingSPARQL queries over the dataset● Caveat: these access method cannot be assumedto be available for all datasets● Creating dumps is not feasible if data changes very frequently● Dumps or endpoints may not be feasible if Linked Datainterface is simply a wrapper for some other data source● Providing and maintaining a reliable SPARQL endpointis a significant additional effort
  11. 11. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 11Outline The Linked Data Principles Paradigms for Querying Linked Data Characteristics of the “Database System”√
  12. 12. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 12Traditional Paradigm 1: Warehousing● Copy data into a centralized repository● Query this repository+ Almost instant results– Misses unknown or new sources– Collection possibly out of date
  13. 13. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 13????Traditional Paradigm 2: Federation● Distribute query execution over afederation of SPARQL endpoints+ Current data– Misses sources withoutSPARQL endpoint
  14. 14. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 14Principle 1: Rely on the Linked Data principles onlyPrinciple 2: On-line executionLinked Data Query Processing
  15. 15. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 15Principle 1: Rely on the Linked Data principles onlyPrinciple 2: On-line executionConsequence: Obtain data for executing a given query bylooking up URIs during the query execution process itselfLinked Data Query Processing
  16. 16. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 16“Ingredients” for LD Query ExecutionQuery-local data
  17. 17. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 17“Ingredients” for LD Query Execution● Data retrieval approach● Data source selection● Data source ranking(optional, for optimization)Query-local dataGET http://.../movie2449
  18. 18. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 18“Ingredients” for LD Query Execution● Data retrieval approach● Data source selection● Data source ranking(optional, for optimization)Query-local datahttp://mdb.../Paul http://geo.../Berlinhttp://mdb.../Ric http://geo.../Rome?loc?actorGET http://.../movie2449● Result construction approach● i.e., query-local data processing
  19. 19. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 19“Ingredients” for LD Query Execution● Data retrieval approach● Data source selection● Data source ranking(optional, for optimization)Query-local datahttp://mdb.../Paul http://geo.../Berlinhttp://mdb.../Ric http://geo.../Rome?loc?actorGET http://.../movie2449● Result construction approach● i.e., query-local data processing● Combining data retrievaland result construction
  20. 20. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 20+ Current data+ May make use of any Linked Data available on the Web– Least efficient due to data shippingUse cases: live querying where freshness and discovery ofresults is more important than an almost instant answerProperties of LD Query Processing
  21. 21. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 21Combination with other Paradigms● Linked Data query processing with a query-local dataset● Query-local dataset contains additional data [LT11]● Query-local dataset for caching [Har11b, HH11]● Linked Data query processing with a SPARQL endpoint● SPARQL endpoint exposes a cache of Linked Data [UKH+12]
  22. 22. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 22Our Topic Today …… pure Linked Data query processingLinked Data query: a query that ranges overdata made available usingthe Linked Data principlesWeb of Linked Data: network of data that evolvesby publishing data accordingto the Linked Data principles
  23. 23. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 23Outline The Linked Data Principles Paradigms for Querying Linked Data Characteristics of the “Database System”√√
  24. 24. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 24An Analogy ...
  25. 25. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 25Traditional, Central Database Systems
  26. 26. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 26Distributed Database Systems
  27. 27. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 27The Web of Linked Data
  28. 28. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 28The Web of Linked Data
  29. 29. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 29● Number ofpotential datasources infiniteThe Web of Linked Data
  30. 30. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 30● Number ofpotential datasources infinite● No (a priori)informationThe Web of Linked Data
  31. 31. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 31● Number ofpotential datasources infinite● No (a priori)informationThe Web of Linked Data
  32. 32. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 32● Number ofpotential datasources infinite● No (a priori)informationThe Web of Linked Data
  33. 33. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 33● Number ofpotential datasources infinite● No (a priori)informationThe Web of Linked Data
  34. 34. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 34● Number ofpotential datasources infinite● No (a priori)informationThe Web of Linked Data
  35. 35. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 35● Number ofpotential datasources infinite● No (a priori)information● Number ofactual datasources infiniteThe Web of Linked Data
  36. 36. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 36Issues due to the Openness● Data quality issues● Accuracy● Freshness / timeliness● Believability / trustworthiness● Data source quality issues● Availability● Reliability● Data integration issues● Coreferences: Publishers may use different URIsfor denoting the same entity● Schema heterogeneity: Publishers may use differentvocabularies for their dataFor the purpose of discussingexecution of queries in this tutorial,we largely ignore these issues.
  37. 37. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 37Outline The Linked Data Principles Paradigms for Querying Linked Data Characteristics of the “Database System”√√√Next part: 2. Theoretical Foundations ...
  38. 38. WWW 2013 Tutorial on Linked Data Query Processing [ Introduction ] 38These slides have been created byOlaf Hartigfor theWWW 2013 tutorial onLink Data Query ProcessingTutorial Website: http://db.uwaterloo.ca/LDQTut2013/This work is licensed under aCreative Commons Attribution-Share Alike 3.0 License(http://creativecommons.org/licenses/by-sa/3.0/)

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