assessing data dissemination strategies
DESCRIPTION
Assessing data dissemination strategies within Triple Spaces on the Web of Things (presentation made on esIoT 2012)TRANSCRIPT
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Assessing data dissemination strategieswithin Triple Spaces on the Web of Things
esIoT 2012
Aitor Gomez-Goiri, Diego Lopez-de-Ipina
DeustoTech - Deusto Institute of Technology, University of Deustohttp://www.morelab.deusto.es
July 4, 2012
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Outline
Introduction
Data dissemination strategies
Evaluation
Conclusions
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Outline
Introduction
Data dissemination strategies
Evaluation
Conclusions
Assessing data dissemination strategies Introduction 3 / 57
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The Web of Things
I Growing connectivity of everyday objects.I WoT to integrate things.
I Scalable interaction, integration with the web world...I But also inherits problems from the web world!
I Lack of expressiveness and human orientationI The Semantic Web enables sharing knowledge across
different applications
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The Semantic Web
The vision of the Semantic Web is to extend principles ofthe Web from documents to data. Data should beaccessed using the general Web architecture using, e.g.,URI-s; data should be related to one another just asdocuments (or portions of documents) are already. Thisalso means creation of a common framework that allowsdata to be shared and reused across application,enterprise, and community boundaries, to be processedautomatically by tools as well as manually, includingrevealing possible new relationships among pieces ofdata. [Con11]
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The Semantic Web
The vision of the Semantic Web is to extend principles ofthe Web from documents to data. Data should beaccessed using the general Web architecture using, e.g.,URI-s; data should be related to one another just asdocuments (or portions of documents) are already. Thisalso means creation of a common framework that allowsdata to be shared and reused across application,enterprise, and community boundaries, to be processedautomatically by tools as well as manually, includingrevealing possible new relationships among pieces ofdata. [Con11]
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Triple Space Computing
I Describes the knowledge shared using the SWI 2 applications using standard ontologies can interact among
them automatically enriching one each other.I Space-based computing
I time autonomyI space autonomyI reference autonomy
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Goal
How to realize this shared blackboard in the IoT?
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Outline
Introduction
Data dissemination strategiesCentralizationNegative broadcastingGossiping based strategy
Evaluation
Conclusions
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Centralization in short
r = |Q| + wf .t .(|N| − 1) (1)
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Negative broadcasting in short
r = |Q|.(|N| − 1) (2)
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How to improve the NB?
Reducing the amount of receivers for a query.
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Problem: how to perfectly predict them withoutknowing all what they know?
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TBox and ABox
According to Nardi and Brachman [NB03]...
TBox contains the knowledge which describes general propertiesof concepts or terminology.
ABox contains knowledge that is specific to the individuals of thedomain of discourse.
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In other words...
With TBox we can describe the type of devices there are in theworld or the sensors they have.
With ABox we can specify that HTC is a mobile brand or that thesensed temperature is 3o C.
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TBox and ABox in IoT scenarios?
I Mobile devices: user profile,...I Sensors and actuatorsI The structure of the data barely changes!
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Our proposal
I We can assume that all the nodes have or can easily obtainthe TBox information.
I Nodes gossip the classes of concepts (rdf:type) shared byother nodes.
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Subject Predicate Object
wot:meas1 rdf:type ssn:N02Observationwot:meas1 ssn:observedProperty sweet:NO2wot:meas1 ssn:observationResult wot:outpt1wot:outpt1 ssn:hasValue wot:val1wot:val1 ssb:QuantityValue 17wot:val1 dul:isClassifiedBy
muo-ucum:microgram-per-cubic-meter... ... ...
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Subject Predicate Object
wot:meas1 rdf:type ssn:N02Observationwot:meas1 ssn:observedProperty sweet:NO2wot:meas1 ssn:observationResult wot:outpt1wot:outpt1 ssn:hasValue wot:val1wot:val1 ssb:QuantityValue 17wot:val1 dul:isClassifiedBy
muo-ucum:microgram-per-cubic-meter... ... ...
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Outline
Introduction
Data dissemination strategies
Evaluation
Conclusions
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Remember
I We wanted to know which strategy fits better for IoT.I Otsopack: our publicly available TSC middleware which uses
HTTP.I Therefore: communication between nodes was point to point
and exchanges data RDF triples.
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Methodology
I Discovery process was ignored.I The Semantic Sensor Network Ontology (SSN).
I Datasets from the University of Utah and the University ofDeusto.
I Measures taken from real embedded web servers.I Simpy.
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Performance Metrics
I Precision: the fraction of nodes which answered relevantresults.
I Recall: the fraction of relevant answers returned.I Response time.
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Outline
Introduction
Data dissemination strategies
Evaluation
Conclusions
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Conclusions
I Need of a gossiping approach.I Increase the precision.I Simulate specific scenarios from the literature.
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Bibliography
World Wide Web Consortium.W3c semantic web faq, August 2011.
D. Nardi and R.J. Brachman.An introduction to description logics.The description logic handbook: theory, implementation, andapplications, pages 1–40, 2003.
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Assessing data dissemination strategies Backup slides 40 / 57
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Semantic Web example
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Write
public String write(String spaceURI, Graph ITriples)
throws TSException;
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Read
public Graph read
(String spaceURI, String graphURI, long timeout)
throws TSException;
public Graph read
(String spaceURI, Template template, long timeout)
throws TSException;
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Take
public Graph take
(String spaceURI, String graphURI, long timeout)
throws TSException;
public Graph take
(String spaceURI, Template template, long timeout)
throws TSException;
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Query
public Graph query(String spaceURI, Template template)
throws TSException;
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Reasoning
Device TBox ABoxRegular computer
2.787 0.045(Sesame 2.6.4)
Samsung Galaxy Tab17.342 0.225
(Sesame 2.4.2)FoxG20
48.939 1.443(Fuxi)
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Our realization of the ideas towards this adaptation areincarnated on Otsopack Open source project
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Otsopack Layers
Each Otsopack instance.
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About HTTP and TSC
The HTTP verbs retrieve, create, modify or delete web resources
The TS primitives retrieve, create, modify or delete RDF graphson a space
(right, to be honest TS also offers a query, which works at space level)
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A RESTful HTTP API
I To expose TS querying primitivesI HTTP status codesI Using content negotiation
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Discovery
I Registry based discoveryI Multicast based implementedI Easy to adopt new ones: DNS, mDNS, lmDNS etc.
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TSC API in depth
HTTP request URLGET /{sp}/query/wildcards/{s}/{p}/{o-uri}
/{sp}/query/wildcards/{s}/{p}/{o-type}/{o-value}GET /{sp}/graphs/{g}GET /{sp}/graphs/wildcards/{s}/{p}/{o-uri}
/{sp}/graphs/wildcards/{s}/{p}/{o-type}/{o-value}DELETE /{sp}/graphs/{g}DELETE /{sp}/graphs/wildcards/{s}/{p}/{o-uri}
/{sp}/graphs/wildcards/{s}/{p}/{o-type}/{o-value}
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XBee gateway platform
I ConnectPort R© X2 (XBee to IPgateway)
I RAM: 8MBI Platform version: Python 2.4I REST libraries: Python Std LibI Semantic libraries: None
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Case of study 1: XBee
I We developed a restricted middleware version using PythonI With more than 15 concurrent requests problems were
experienced
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FoxG20 platform
I Processor: 400Mhz Atmel ARM9I RAM: 64MBI Platform version: Python 2.5I REST libraries: Python Std LibI Semantic libraries: Fuxi
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Case of study 2: FoxG20
I Python implementation usedI Because is lighterI Does not implement all the modules definedI This may be desirable for less powerful devices
I Reasoning took a long timeI TBox: x17 regular computer, x2 galaxy tabI ABox: x32 - x6 galaxy tab
⇓should be limited to special occasions
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