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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

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Things, Data, and lots of it

image courtesy: Smarter Data - I.03_C by Gwen Vanhee

We need more linked open data

(near) real-time linked open data Streams

Sometimes it’s even better if we have:

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The world of IoT and Semantics

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 Descriptions in Semantic (Web) World

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Semantic Web these days…

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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)

Several ontologies and description models

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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…

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Publishing Linked Data

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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Simplicity can be very useful…

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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

Make your model fairly simple and modular

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SSNO model

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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…

Static Semantics

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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.

CityPulse Ontologies: Stream Annotation Ontology

CityPulse Ontologies: Quality Ontology

CityPulse Ontologies: Complex Event Processing Ontology

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Validation of sensory linked data

• 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

Related Ontologies and Terms to the SSN Ontology

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SSN

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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

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Hands on Session!

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Link for the hands on session: http://iot.ee.surrey.ac.uk/citypulse/ontologies/sao/saopy.html

− Thank you.

− EU FP7 CityPulse Project:

http://www.ict-citypulse.eu/

@ictcitypulse

s.kolozali@surrey.ac.uk &

p.barnaghi@surrey.ac.uk