1. Finding Data Sets
Anja Jentzsch, Freie Universität Berlin
17 April 2012
Tutorial: Practical Cross-Dataset Queries on the Web of Data
WWW2012, Lyon, France
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2. Different motivations
• Finding data sets
• Look for resources to link a data set to
• Find a data set with relevant data to consume / integrate
• Finding vocabularies
• Find vocabularies to use to model data sets
• Find vocabularies to map your existing schema to
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3. Different tool types
• Search engines
• find data sets based on keywords
• Data catalogs / directories
• explore data sets and faceted search
• Data Marketplaces
• explore and consume data sets
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4. Linked Data Search Engines
• The description of the resources is published as document in RDF
• RDF search engine index the RDF documents
• Process similar to that of search engines for HTML documents
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5. http://sindice.com 5

6. http://sindice.com 6

7. http://sig.ma 7

8. http://sig.ma 8

9. http://swoogle.umbc.edu 9

10. http://kmi-web05.open.ac.uk/WatsonWUI/ 10

11. http://factforge.net 11

12. http://factforge.net 12

13. Suitability
• Look for resources to link a data set to
• Good
• Find a data set with relevant data to consume
• Maybe good: depends on how the query is expressed
• Find vocabularies to use to model data sets
• Not good: everything is indexed, too much noise
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14. Data catalogs
• Several governments and institutions are opening their catalogs
• http://datacatalogs.org provides a manually curated index of 226 data catalogs
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15. http://datacatalogs.org 15

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17. The Data Hub
• Manually curated list of (>3.500) data sets, at least 326 Linked Data Sets
• Various metadata for each data set
• Other views over (part of) its content
• Semantic CKAN (http://semantic.ckan.net)
• LATC Data Source Inventory
• LOD Cloud
• State of the LOD Cloud
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18. http://thedatahub.org 18

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20. http://dsi.lod-cloud.net 20

21. http://lod-cloud.net 21

22. http://lod-cloud.net/state/ 22

23. http://lod-cloud.net/state 23

24. Data Marketplaces
• “Services that make it easy to find data from a range of secondary data sources,
then consume or acquire the data in a usable and unified format. Several of these
services are trying to create marketplaces for data, envisioning that data providers
can offer their data sets for sale to data seekers.” (http://datamarket.com)
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25. Kasabi
• Data domain
• All purpose, incl. DBpedia, GeoNames, BBC Linked Data, …
• Data population
• Public datasets
• User submitted datasets
• Data size
• 186 data sets
• Data model
• RDF
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26. http://kasabi.com 26

27. Freebase
• Metaweb (USA), now Google
• Free for 100K read API calls per day (10K write), paid for higher volumes
• Data access
• REST API
• Linked Data endpoint (http://rdf.freebase.com)
• Triple uploader / RDF dumps
• Data tools
• Web based – schema editor, review queue, viewers, …
• GridWorks (Google Refine)
• Exploring, data cleaning, transformation of tabular data
• Map data to Freebase schema & RDF export (3rd party extension) 27

28. http://www.freebase.com 28

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30. Linked Open Vocabularies (LOV)
• Initiative similar to the LOD Cloud but focused on vocabularies
• 250+ vocabularies
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31. http://labs.mondeca.com/dataset/lov/ 31

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