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Virtualisation and Validation of Smart City Data
Dr Sefki KolozaliInstitute for Communication SystemsElectronic Engineering Department
University of Surrey
Dr Payam BarnaghiInstitute for Communication SystemsElectronic Engineering Department
University of Surrey
Semantics & the IoT
− The Semantic Sensor (&Actuator) Web is an extension of the current Web/Internet in which information is given well-defined meaning, better enabling objects, devices and people to work in co-operation and to also enable autonomous interactions between devices and/or objects.
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Semantic Sensor Web
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“The semantic sensor Web enables interoperability and advanced analytics for situation awareness and other advanced applications from heterogeneous sensors.” (Amit Sheth et al, 2008)
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We have good models and description frameworks;
The problem is that having good models and developing ontologies is not enough.
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Semantic descriptions are intermediary solutions, not the end product.
They should be transparent to the end-user and probably to the data producer as well.
A WoT/IoT Framework
WSN
WSN
WSN
WSN
WSN
Network-enabled Devices
Semantically annotate data
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GatewayCoAP
HTTP
CoAP
CoAP
HTTP
6LowPAN
Semantically annotate data
http://mynet1/snodeA23/readTemp?
WSN
MQTT
MQTT
Gateway
And several other protocols and solutions…
Understanding the principles of Linked Data
− It really is all about applying Tim Berners Lee's 4 rules to encourage re-use of data− use URIs as the names of things− use HTTP URIs so we can look them up− provide useful RDF when things are looked up− link to other URIs to facilitate discovery
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6 steps to publishing Linked Data
− Understand the principles− Understand your data− Choose URIs for Things in your data− Setup your infrastructure− Link to other data sets− Describe and publicize your data
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Key Points for Publishing Semantic annotations
− We need a model (ontology) – this is often the easy part for a single application.
− Interoperability between the models is a big issue. − Express-ability vs Complexity is a challenge
− How and where to add the semantics− Where to publish and store them− Semantic descriptions for data, streams, devices
(resources) and entities that are represented by the devices, and description of the services.
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Complex models are (sometimes) good for publishing research papers….
But they are often difficult to implement and use in real world products.
What happens afterwards is more important
− How to index and query the annotated data− How to make the publication suitable for constrained
environments and/or allow them to scale− How to query them (considering the fact that here we are
dealing with live data and often reducing the processing time and latency is crucial)
− Linking to other sources
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The IoT is a dynamic, online and rapidly changing world
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isPartOf
Annotation for the (Semantic) Web
Annotation for the IoT
Image sources: ABC Australia and 2dolphins.com
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Semantic descriptions can be fairly static on the Web;
In the IoT, the meaning of data and the annotations can change over time/space…
Dynamic Semantics
<iot:measurement><iot:type> temp</iot:type><iot:unit>Celsius</iot:unit><time>12:30:23UTC</time><iot:accuracy>80%</iot:accuracy><loc:long>51.2365<loc:lat><loc:lat>0.5703</loc:lat></iot:measurment>
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But this could be a function of time and location;
What would be the accuracy 5 seconds after
the measurement?
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Some good existing models: SSN Ontology
Ontology Link: http://www.w3.org/2005/Incubator/ssn/ssnx/ssn
M. Compton et al, "The SSN Ontology of the W3C Semantic Sensor Network Incubator Group", Journal of Web Semantics, 2012.
Dynamic annotations for provenance data
27S. Kolozali et al, A Knowledge-based Approach for Real-Time IoT Data Stream Annotation and Processing", iThings 2014, 2014.
• To check RDF descriptions• To enable user to validate an ontology or Linked Data
• Undefined classes and properties• Poorly formed namespaces• Problematic prefixes• Literal syntax validation and other
optional heuristics
Validation of Sensory Linked Data
The architecture of the SSN Validator web application
Available at: http://iot.ee.surrey.ac.uk/SSNValidation/
A screenshot of the SSN Validation web application
Available at: http://iot.ee.surrey.ac.uk/SSNValidation/
Tag Cloud Representation of the Related Terms
Available at: http://iot.ee.surrey.ac.uk/SSNValidation/
• SPITFIRE• :SavedEnergyOf rdfs:domain :SavedEnergy• :value rdf:type owl:ObjectProperty ;
rdfs:domain :OV ; ssn:subPropertyOf qudt:numericValue ; rdfs:isDefinedBy <http://spitfire-project.eu/ontology/ns> .
• IoT.est and SemsorGridEnv• @prefix ssn: <http://purl.org/ifgi/ssn#> .
• OntoSensor• :event_Description
a owl:FunctionalProperty , owl:DatatypeProperty ; rdfs:domain :Event ; rdfs:range xsd:string .
Some examples from the validation outputs:SavedEnergyOfis NOT defined!
Wrong URIs have been used!
ssn:subPropertyOf is used instead of rdfs:subPropertyOf
Needs to be updated: OWL-2 guidelines - FunctionalDataProperty
− Thank you.
− EU FP7 CityPulse Project:
http://www.ict-citypulse.eu/
@ictcitypulse