Linked Open Data projects aim to extend the web of documents to a web of linked data by adding semantics through standards like RDF and ontologies. The Linked Open Data cloud has grown significantly since 2007 and contains billions of RDF triples and links between data sources. Projects like LOD2 build on this by developing technologies and linking more open datasets to enable new applications. For Linked Data to achieve its full potential, openness and allowing free access and reuse is important, though it does mean losing some control over data usage.

1. Linked Open Data: Principles & 2 Projects Prof. Dr. Stefan Gradmann Humboldt-Universität zu Berlin / School of Library and Information Science [email_address]

2. Overview Linked Data: What is it, how does it work?

3. LoD & LOD2: two projects

4. Conclusion : on the importance of being 'open'

5. From the Web of Documents to the Linked Data Web The Document Web: Information Management: A Proposal (TBL, 1989). Built on Documents („Information Resources“)

6. Untyped HTTP links The Web of Linked Open Data can be understood as an extension of the document web In syntax (RDF)

7. In scope (including re- presentations of non- information resources, 'things', 'data')

8. Syntactically Extending the Document Web (1) We add a syntax for making statements on resources: RDF Or, more generally triples ... … where S and P are web resources (identified using URIs) and O is either a web resource or a literal

9. Syntactically Extending the Document Web (2) We add a schema language (RDFS) with elements such as classes,

10. hierarchies of classes and properties,

11. inheritance

12. support for basic inferencing. And thus are able to establish structures in triple aggregations resulting in lightweight domain ontologies:

13. Extending the Web in Scope: the way it does not work! Taken from Ronald Carpentier's Blog at http://carpentier.wordpress.com/ 2007/08/08/1-2-3/ Something is wrong with this picture (but what?)

14. … and the way extending the Web in scope is actually done: A Web of Things

15. … Linked Data Copyright © 2008 W3C (MIT, ERCIM, Keio) http://www.w3.org/2008/Talks/0617-lod-tbl/#(4) Standard Identifiers Standard Pointers Standards for Queries and Statements Link to Context

16. A few Bubbles: 5/2007 < Over 500 million RDF triples < Around 120,000 RDF links between data sources © Richard Cyganiak

17. Quite some Bubbles: 9/2008 © Richard Cyganiak

18. Many Bubbles: 7/2009 © Richard Cyganiak < Over 13.1 billion RDF triples < Over 142 million RDF links between data sources

19. (Too?) Many Bubbles: 9/2010 http://richard.cyganiak.de/2007/10/lod/lod-datasets_2010-09-22_colored.html