1. (Geospatial Semantics)
ANUSURIYA DEVARAJU
Institute for Geoinformatics,
University of Muenster.
Muenster
(anusuriya.devaraju@uni-muenster.de)
2. Definitions : Sensor Web (OGC, NASA)
OGC Sensor Web Enablement (SWE)
( )
SWE Specifications
How SWE Works? An Example…
Semantic Sensor Web & Motivating Example
Architecture
Approach
– Semantic Annotation
– Ontologies (Sensors, Observations, Space, Time, Domain-specific)
– Rules-based Reasoning
2
3. A Sensor Web consists of intra-communicating, spatially-
distributed sensor pods that are deployed to monitor and explore
environments [NASA New Technology Report on Sensor Webs]
Information sharing among
the pods
Intelligent autonomous
operations ( d t and react)
ti (adapt d t)
Source: Delin K and Jackson S, (2001) , The Sensor Web: A New Instrument Concept 3
4. Sensor Web refers to web accessible sensor networks and
archived sensor data that can be discovered and accessed using
standard protocols and application program interfaces [Botts et al. , 2006]
Sensor Web concept (OGC, 2006)
Source: M. Botts, G. Percival, C. Reed, J. Davidson (2006) , OGC SWE : Overview and High Level Architecture 4
5. Sensors and sensor observations will be web accessible and
discoverable through standardized web services
Sensors will be self-describing to humans and software using
standard encodings
Most sensor observations will be easily accessible in near real
time over the web
Real-time mining of observations to find phenomena of immediate
interest
i t t
Sensor systems will be capable of issuing alerts based on
observations, as well as be able to respond to alerts issued by
other sensors
Source: M.Botts and Robin A, (2007), Bringing the Sensor Web Together 5
6. Software will be capable of on-demand geo-location and
processing of observations from a newly-discovered sensor
without a priori knowledge of that sensor system
Sensors, simulations, and models will be capable of being
configured and tasked through standard, common web interfaces
The semantics of sensor web components will be tied to well-
defined ontologies that will allow better understanding of potential
relationships between systems
Source: M.Botts and Robin A, (2007), Bringing the Sensor Web Together 6
7. The role of Sensor Web Enablement for supporting heterogeneous
sensors, models, simulations, and decision support tools.
Enable interoperability
between disparate sensor
types, disciplines,
types disciplines and
agencies.
Leverage benefits of open
standards
d d
Service Oriented
Architecture (SOA) based
( )
Virtually any sensor or
modeling system can be
supported
Source: M.Botts (2008), OGC Sensor Web Enablement (Intro) - Presentation Slides 7
8. Information Encodings
– Observations & Measurements (O&M) : The general models and XML
encodings for observations and measurements.
– Sensor Model Language (SensorML) : Standard models and XML Schema
for describing the processes within sensor and observation processing
systems.
– Transducer Markup Language (TML) : Conceptual model and XML encoding
for supporting real-time streaming observations and tasking commands from
and to sensor systems.
Source: M.Botts (2008), OGC Sensor Web Enablement (Intro) - Presentation Slides 8
10. Web Services
– Sensor Observation Service: Access Observations for a sensor or sensor
constellation, and optionally, the associated sensor and platform data
– Sensor Alert Service : Subscribe to alerts based upon sensor observations
– Sensor Planning Service : Request collection feasibility and task sensor
system for desired observations
– Web Notification Service : Manage message dialogue between client and
Web service(s) for long duration ( y
( ) g (asynchronous) processes
)
– Sensor and Observation Registry : Common interface for discovery of
sensor systems, processes, models, and observations
Source: M.Botts (2008), OGC Sensor Web Enablement (Intro) - Presentation Slides 10
11. (
(Sensor Observation Service Concept)
p)
Source: http://www.sensorsportal.com/HTML/DIGEST/september_06/P_84.pdf 11
17. SWE specifications enables a wider access to sensors and
observations. Nevertheless, an effort is required to collate and
interpret th
i t t them..
Observation Archives
Stream
DPIPWE Flow
Current
C t
XML stream flow
data at river
HydroTas X?
WaterCourse
WDS Discharge
XML
Stream
Discharge
XML
SWE Client
Sensor Collection Service
17
18. A framework that extends SWE and Semantic Web technologies
to provide enhanced meaning to sensor data
– How? Annotate sensor data with spatial, temporal and thematic semantic
metadata
Source: Sheth A and Henson C, 2008, Semantic Sensor Web 18
21. Embedding semantics in an XML document using RDFa
<swe:component rdfa:about=“time_1”
rdfa:instanceof=”time:Instant”>
<swe:Time rdfa:property=“xs:date-time”>20080308T05:00:00
</swe:Time>
</ Ti >
</swe:component>
(a timestamp encoded in O&M and semantically annotated with RDFa)
rdf:type
time_1
time 1 time:Instant
xs:date-time 20080308T05:00:00
Source: Sheth A and Henson C, 2008, Semantic Sensor Web 21
22. Creating internal and external links within XML documents using
XLink (XML Linking Language)
(Semantic annotation of O&M with XLink)
Source: http://geostandards.geonovum.nl/index.php/5.3.2_O%26M 22
23. Sensor and Sensing Procedure : W3C SSN Incubator, NIST Sensor Standards
Harmonization, OntoSensor, CESN ontology, SWAMO, ….
Observation : O&M ontology, Functional Ontology of O&M…
gy, gy
Units of Measurements : UCUM Units, SWEET Units, QUDT, …
Spatial : GML Ontology..
Temporal: W3C Time Ontology,
p gy,
Valid-Time Temporal Ontology..
Sensed domain (thematic) :
*Domain- specific ontologies
p g
Image: Sheth A and Henson C, 2008, Semantic Sensor Web 23
24. Point measurements performed by an instrument
(e.g., evaporation pan)
The partial view of the Sensor Network Ontology (SNO)
Source: Devaraju A, et al. (2010), Combining Process and Sensor Ontologies to Support Geo-Sensor Data Retrieval 24
25. Incorporates rules into an ontology schema to derive additional
knowledge from semantically annotated sensor data
[Environment Canada] A blizzard must have winds of 40 km/h or more,
have snow or blowing snow, visibility less than 1 km and a windchill of less
than -25 degrees celsius All of these conditions must last for 4 hours or more
25 celsius. more.
WindSpeed(a) ≥ 40km/h Duration(a) ≥ 4hours
Visibility(b) ≤ 1km Duration(b) ≥ 4hours
WindChill(c) < -25◦C Duration(c) ≥ 4hours
→ Blizzard(x)
25
