Sensor data is stored and published using OGC’s Observation & Measurement specifications as underlying data model. With the advent of volunteered geographic information and the Semantic Sensor Web, work on an ontological, i.e. conceptual, model gains importance within the Sensor Web Enablement community. In contrast to a data model, an ontological approach abstracts from implementation details by focusing on modeling the real world from the perspective of a particular domain or application and, hence, restricts the interpretation of the used terminology towards their intended meaning. The shift to linked sensor data, however, requires yet another perspective. Two challenges have to be addressed, (i) how to refer to changing and frequently updated data sets such as stored in Sensor Observation Services using Uniform Resource Identifiers, and (ii) how to establish meaningful links between those data sets, i.e., observations, sensors, features of interest, observed properties, and further participants in the measurement process. In this short paper we focus on the problem of assigning meaningful URIs. Get the paper here: http://ifgi.uni-muenster.de/~arneb/de2010_final_submission.pdf

1. Towards Meaningful URIs
for Linked Sensor Data
K. Janowicz, A. Broering, C. Stasch, T. Everding
Towards Digital Earth Workshop @ FIS2010, Berlin
September 20th, 2010

2. Vision
 World Wide Web is for websites
 HTTP
 HTML
 ...
 Sensor Web is for sensors
 O&M
 SOS
 SPS
 ...
Arne Broering - broering@52north.org

3. Sensor Web Enablement (SWE)
®
OGC
 http://www.ogcnetwork.net/swe
 Web Service interfaces & data encodings
 Building blocks for a Sensor Web
Arne Broering - broering@52north.org

4. SWE Functionality

5. Project: GITEWS

6. Sensor Observation Service
GetCapabilities
SensorML DescribeSensor
O&M GetObservation
GML GetFeatureOfInterest
Arne Broering - broering@52north.org

7. Observations & Measurements
Observed Property:= „Windspeed“ Sampling Time
Result
Feature of Interest:= „SeminarisHotelBerlin“ 23 m/s 16.9.2010 13:45
Unit of Measure
Sensor := „Weatherstation_Dahlem“
Observation
Arne Broering - broering@52north.org

8. Observations & Measurements
class O&M
Observ ation Any
+result
- samplingTime: Time
1
0..*
+propertyValueProvider
+procedure +observedProperty +featureOfInterest
1 1
1
Procedure PropertyType «FeatureType»
AnyFeature
Arne Broering - broering@52north.org

9. Goal: Linked Sensor Data
To improve browsing & discovery of sensor data
Arne Broering - broering@52north.org

10. Vision
 World Wide Web is for websites / documents
 HTTP
 HTML
 ...
 Sensor Web is for sensors
 SOS
 O&M
 ...
 Linked Data Web is for linked data
 RDF
 ...
Arne Broering - broering@52north.org

11. Linked Data
 Shift from linked documents to linked data
 Establish links:
 Documents: HTML
 Data: RDF
 Already available linked data:
 people, companies, publications, books, movies, music, television
programs, genes, proteins…
Arne Broering - broering@52north.org

12. Linked Data
 Example usage:
 What proteins are involved in signal transduction AND are
related to pyramidal neurons?
 Google search: 200.000 hits, NO results
 Linked Data search: 32 hits, 32 results
(see TED Talk from Berners-Lee)
 Example “GEO”-usage:
 Which sensors are located along the river Rhine AND
measure water level higher than 4,50 m during yesterday?
Arne Broering - broering@52north.org

13. Linked Sensor Data
 Requirements
 Linked Data Model (in RDF)
 Links between data chunks
 Unified Resource Identifier (URI) Scheme
Arne Broering - broering@52north.org

14. RESTful SOS Proxy for Linked Sensor Data
Arne Broering - broering@52north.org

15. URI Scheme for Linked Sensor Data
 Access to features of interest:
http://my.authority.org/foi
 Example:
http://my.authority.org/foi/SeminarisHotelBerlin
 Access to sensors:
http://my.authority.org/sensors
 Example:
http://my.authority.org/sensors/Weatherstation_Dahlem
Arne Broering - broering@52north.org

16. URI Scheme for Linked Sensor Data
 Access to observations:
http://my.authority.org/observations
 Thematic filter:
../observation/<sensor>/<foi>/<observed property>
 Example:
../observations/Weatherstation_Dahlem/SeminarisBerlin/windSpeed
 Example “Wildcard”:
../observations/-/-/windSpeed
Arne Broering - broering@52north.org

17. URI Scheme for Linked Sensor Data
 Temporal filter (aligned with ISO8601):
../observation/sensor/foi/observed property/<start date>/<end date>
<start date>:= <year>/<month>/<day>/<hour>/<minute>/<second>
<end date> := <year>/<month>/<day>/<hour>/<minute>/<second>
 Example:
February 2010 - 1st July 2010 at 13:05:
../2010/02/-/-/-/-/2010/07/01/13/05/-/..
Arne Broering - broering@52north.org

18. URI Scheme for Linked Sensor Data
 Spatial filter:
../<start>/<end>/<minLat>_<minLong>_<maxLat>_<maxLong>_<crs>
 Example:
../52.12_7.45_52.34_7.56_urn:ogc:def:crs:EPSG::4326
Arne Broering - broering@52north.org

19. RESTful SOS Architecture
Arne Broering - broering@52north.org

20. Outlook
 Linked Data model (O&M  RDF)
 Accepted by W3C Semantic Sensor Network Incubator Group
(http://www.w3.org/2005/Incubator/ssn/)
 Meaningful Links within model
 Include other SWE standards:
 SensorML  RDF
 RESTful SES Proxy
Arne Broering - broering@52north.org

21. Demo: RESTful SOS Proxy
http://v-swe.uni-muenster.de:8080/52n-OXF-WS/RESTful/sos

22. Questions?
Thank you!
Arne Broering
broering@52north.org
52°North RESTful SOS Proxy: http://52north.org/RESTFul_SOS
52°North Semantics Community: http://52north.org/semantics
IfGI SWSL: http://swsl.uni-muenster.de
IfGI MUSIL: http://musil.uni-muenster.de