aggregating linked sensor data
DESCRIPTION
This presentation was given at the Semantic Sensor Networks Workshop at the International Semantic Web Conference (ISWC) 2011. It shows our approach for Aggregating Linked Sensor Data.TRANSCRIPT
Aggregating Linked Sensor Data
Christoph Stasch, Sven Schade, Alejandro Llaves, Krysztof Janowicz, Arne Bröring
Institute for GeoinformaticsWestfälische Wilhelms-Universität Münster
3rd Workshop on Semantic Sensor NetworksBonn, 2011
Christoph Stasch – [email protected]
Aggregation in Linked Sensor Data
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Adding new links:Belongs the observation value to that feature?
Spatial Aggregation
15,5°CLinking the aggregatedobservation
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Aggregation• Aggregation:
• An aggregation process computes a value, an aggregate, for a group of attribute values by means of an aggregation function. The attribute values are grouped by a partitioning predicate.
• Aggregation Function: • Function used to compute the aggregate.
• Partitioning Predicate: • Predicate used to group objects before aggregating the
values attached to these objects.
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Spatio-temporal vs. Thematic Aggregation
• Spatio-temporal Aggregation: – Partitionining predicate is spatial and/or temporal
• Thematic Aggregation:– Partitioning predicate operates on attribute values
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Linked Sensor Data• 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
• Linked Sensor Data (e.g. Page 2009)
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RESTful SOS Proxy• Proxy service for Sensor Observation Services• Linked data model + URI scheme for observation
resources
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Janowicz, K., Bröring, A., Stasch, C., Schade, S., Everding, T., and Llaves, A. (2011): A RESTful Proxy and Data Model for Linked Sensor Data. International Journal of Digital Earth. DOI:10.1080/17538947.2011.614698, pp. 1-22
Spatio-Temporal Aggregation Service(STAS)
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Stasch, C., Autermann, C., Foerster, T., Pebesma, E.: Towards a Spatiotemporal Aggregation Service in the Sensor Web. Poster Presentation. In: The 14th AGILE International Conference on Geographic Information Science. (2011)
Aggregating Linked Sensor Data
• Linked Data Model:– Extending the SSO pattern to allow aggregated
observations
• Effects on Links from and To Observations– How do links change during aggregation?
• Provenance– Information is contained in Linked Data Model; can be
mapped to Open Provenance Model or Provenance Vocabulary
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Effects on Links from and to Observations
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Spatial Aggregation
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Provenance Information• Common approaches:
– Open Provenance Model• Nodes and edges to define provenance graphs
– Provenance Vocabulary
• Provenance in Sensor Data:– Information about the source of the data as well as
transformations applied– Approaches
• Provenance in Linked Sensor Data• Using OPM for sensor data• Defining own provenance models
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Provenance
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DUL = Dolce Ultra Lightldm = Linked Sensor Data Modelopmv = Open Provenance Model Vocabularyprv = Provenance Vocabulary
Conclusions• Aggregation helps:
– Establishing new links– Fusing datasets
• Extended SSO pattern– Allows for aggregated observations and aggregation
processes– Retracing aggregated Observations back to original
observations mapping to OPM and Provenance Vocabulary
• Effects of aggregation on links from and to observations
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Outlook• Formalize effects of aggregation on links• Enable Spatio-temporal Aggregation Service for
linked sensor data• Integrate with approaches for sensor plug‘n‘play
and linked sensor streams• Utilize semantics of aggregation processes• Integrate uncertainty/quality information
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Discussion• To what aggregation level can we speak of
observations?• Virtual sensors vs. Physical Sensors?• Common aggregation mechanisms in Linked
Data?
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Thank you!
RESTful SOS:http://52north.org/communities/sensorweb/clients/OX_RESTful_SOS/index.htm
STAS:
https://wiki.aston.ac.uk/foswiki/bin/view/UncertWeb/Spatio-temporalAggregationService
http://www.uncertweb.org
http://www.envirofi.org
http://www.envision-project.eu
http://irtg.ifgi.de
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