Post on 14-Dec-2014
description
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 – staschc@uni-muenster.de
Introduction
Christoph Stasch – staschc@uni-muenster.de
2
Aggregation in Linked Sensor Data
15°C
16°C 17°C
14°C
Adding new links:Belongs the observation value to that feature?
Spatial Aggregation
15,5°CLinking the aggregatedobservation
Christoph Stasch – staschc@uni-muenster.de
3
Spatio-temporal and Thematic Aggregation
Christoph Stasch – staschc@uni-muenster.de
4
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.
Christoph Stasch – staschc@uni-muenster.de
5
Spatio-temporal vs. Thematic Aggregation
• Spatio-temporal Aggregation: – Partitionining predicate is spatial and/or temporal
• Thematic Aggregation:– Partitioning predicate operates on attribute values
Christoph Stasch – staschc@uni-muenster.de
6
Previous Work
Christoph Stasch – staschc@uni-muenster.de
7
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)
Christoph Stasch – staschc@uni-muenster.de
8
RESTful SOS Proxy• Proxy service for Sensor Observation Services• Linked data model + URI scheme for observation
resources
Christoph Stasch – staschc@uni-muenster.de
9
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)
Christoph Stasch – staschc@uni-muenster.de
10
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
Christoph Stasch – staschc@uni-muenster.de
11
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
Christoph Stasch – staschc@uni-muenster.de
12
Extended SSO Design Pattern
Christoph Stasch – staschc@uni-muenster.de
13
Effects on Links from and to Observations
Christoph Stasch – staschc@uni-muenster.de
14
15°C
16°C 17°C
14°CFOI1
FOI2
FOI3
FOI4
Spatial Aggregation
15,5°C
Effects from and to Observations
Christoph Stasch – staschc@uni-muenster.de
15
Provenance
Christoph Stasch – staschc@uni-muenster.de
16
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
Christoph Stasch – staschc@uni-muenster.de
17
Provenance
Christoph Stasch – staschc@uni-muenster.de
18
DUL = Dolce Ultra Lightldm = Linked Sensor Data Modelopmv = Open Provenance Model Vocabularyprv = Provenance Vocabulary
Conclusions & Outlook
Christoph Stasch – staschc@uni-muenster.de
19
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
Christoph Stasch – staschc@uni-muenster.de
20
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
Christoph Stasch – staschc@uni-muenster.de
21
Discussion
Christoph Stasch – staschc@uni-muenster.de
22
Discussion• To what aggregation level can we speak of
observations?• Virtual sensors vs. Physical Sensors?• Common aggregation mechanisms in Linked
Data?
Christoph Stasch – staschc@uni-muenster.de
23
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
Christoph Stasch – staschc@uni-muenster.de
24