1. Linked Data Practices for the Geospatial Community Talk subtitle Presented at GEOSS Workshop on Climate Boulder Colorado, 23 September 2011 Stephan Zednik, zednis@rpi.eduzednis@rpi.edu RPI / Tetherless World Constellation

2. Value Proposition of Linked Data Discover –Web resources ‘easy’ to generate and link to Access –Leverage HTTP methods Integrate –RDF is a standard mechanism for specifying the existence and meaning of connections between items described in the data Use –Web standards for data access and representation simplify data consumption while providing (extreme) expressivity

3. Principles of Linked Data There are 4 principle expectations (rules) for Linked Data 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

4. World Wide Web of Data!

5. Linked Data Languages SKOS (Simple Knowledge Organizational System) –Thesauri, Taxonomies, Topical Hierarchies RDFS (RDF Schema) –Vocabularies OWL (Web Ontology Language) –Ontologies RDFS+ –RDFS + Subset of OWL

6. Reuse Key factor in re-usability of data: structure Regular and structured is –Easier to find –Easier to make tools for –More likely to be referenced and therefore beneficiary of network effect

7. Re-use Concerns Usage & Uptake Maintenance & Governance Coverage Expressivity Modularity

8. Example: SWEET 2 Dependency Graph

9. Finding Vocabularies No current definitive directory to find existing vocabularies –SchemaWeb, SchemaCache, Swoogle Statistics on usage of vocabularies in the wild –Section 2.3 of the State of the LOD Cloud –http://lod-cloud.net/state#termshttp://lod-cloud.net/state#terms

10. Using Vocabularies If suitable terms are found, they should be re-used –Maximizes potential for consumption –Network effect on re-used vocabulary New terms should be mapped to well- established existing vocabularies –Standards bodies useful to establish & promote vocabularies –Network effect long-term driving factor Example: FOAF

11. W3C Geo Vocabulary Basic RDF vocabulary that provides a namespace for representing latitude, longitude, and other spatially located things using WGS84 as a reference datum –http://www.w3.org/2003/01/geo/http://www.w3.org/2003/01/geo/ –Wide usage, but far too simple for GIS tools <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#"> 55.701 12.552

12. OGC GeoSPARQL Includes –RDF/OWL Vocabulary for representing spatial information –A set of functions for spatial computations –A set of query transformation Rules Expressivity for GIS tool requirements http://www.opengeospatial.org/projects/ groups/geosparqlswghttp://www.opengeospatial.org/projects/ groups/geosparqlswg

13. OGC GeoSPARQL RDF

14. Discovering Linked Data ‘Standard’ discovery of linked data is via other linked data… OpenSearch –Version 1.1 Geo extension (very basic) –Semantics? DataCasting –ProductCasting –InventoryCasting ServiceCasting

15. Querying Linked Data SPARQL Endpoint –Requires understanding of structure –Generally domain agnostic Faceted Browsing –Pelorus http://clarkparsia.com/pelorus –S2S http://tw.rpi.edu/web/project/sesf/workinggroups /s2shttp://tw.rpi.edu/web/project/sesf/workinggroups /s2s Supports Widgets

16. SPARQL Endpoint Web Browser

17. Pelorus

18. S2S Faceted Browser

19. Services & Linked Data SOAP Web Services and Linked Data are not complementary –Document exchange vs Web of Data –SOAP ignores HTTP access semantics REST (Representational State Transfer) –HTTP as a mechanism for retrieval of resource representations exposed via URIs –Resource Orientated Architecture (ROA) –Stateless interactions Linked Data and RESTful services can be complementary –Will take care in design

20. Questions? Stephan Zednik, zednis@rpi.eduzednis@rpi.edu

21. References Tom Heath and Christian Bizer (2011) Linked Data: Evolving the Web into a Global Data Space (1 st Edition) Synthesis Lectures on the Semantic Web: Theory and Technology, 1:1, 1-136. Morgan & Claypool. –DOI: 10.2200/S00334ED1V01Y201102WBE001 –http://linkeddatabook.com/editions/1.0/http://linkeddatabook.com/editions/1.0/ GeoSPARQL SWG –http://www.opengeospatial.org/projects/groups/geosparqlswghttp://www.opengeospatial.org/projects/groups/geosparqlswg JPL Datacasting –http://datacasting.jpl.nasa.gov/http://datacasting.jpl.nasa.gov/ Pelorus –http://clarkparsia.com/pelorushttp://clarkparsia.com/pelorus S2S –http://tw.rpi.edu/web/project/sesf/workinggroups/s2shttp://tw.rpi.edu/web/project/sesf/workinggroups/s2s