Assessing data dissemination strategies

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

http://www.morelab.deusto.es

Outline

Introduction

Data dissemination strategies

Evaluation

Conclusions

Assessing data dissemination strategies 2 / 57

Outline

Introduction


Evaluation

Conclusions

Assessing data dissemination strategies Introduction 3 / 57

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


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]


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]


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


Goal

How to realize this shared blackboard in the IoT?


Outline

Introduction

Data dissemination strategiesCentralizationNegative broadcastingGossiping based strategy

Evaluation

Conclusions

Assessing data dissemination strategies Data dissemination strategies 10 / 57

Centralization in short

r = |Q| + wf .t .(|N| − 1) (1)


Negative broadcasting in short

r = |Q|.(|N| − 1) (2)


How to improve the NB?

Reducing the amount of receivers for a query.


Problem: how to perfectly predict them withoutknowing all what they know?

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.


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.


TBox and ABox in IoT scenarios?

I Mobile devices: user profile,...I Sensors and actuatorsI The structure of the data barely changes!


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.


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... ... ...

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... ... ...

Outline

Introduction


Evaluation

Conclusions

Assessing data dissemination strategies Evaluation 29 / 57

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.


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.


Performance Metrics

I Precision: the fraction of nodes which answered relevantresults.

I Recall: the fraction of relevant answers returned.I Response time.


Outline

Introduction


Evaluation

Conclusions

Assessing data dissemination strategies Conclusions 36 / 57

Conclusions

I Need of a gossiping approach.I Increase the precision.I Simulate specific scenarios from the literature.



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.

Assessing data dissemination strategies Bibliography 39 / 57

Assessing data dissemination strategies Backup slides 40 / 57

Semantic Web example


Write

public String write(String spaceURI, Graph ITriples)

throws TSException;


Read

public Graph read

(String spaceURI, String graphURI, long timeout)

throws TSException;

public Graph read

(String spaceURI, Template template, long timeout)

throws TSException;


Take

public Graph take

(String spaceURI, String graphURI, long timeout)

throws TSException;

public Graph take

(String spaceURI, Template template, long timeout)

throws TSException;


Query

public Graph query(String spaceURI, Template template)

throws TSException;


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)


Our realization of the ideas towards this adaptation areincarnated on Otsopack Open source project

http://code.google.com/p/otsopack/

Otsopack Layers

Each Otsopack instance.


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)


A RESTful HTTP API

I To expose TS querying primitivesI HTTP status codesI Using content negotiation


Discovery

I Registry based discoveryI Multicast based implementedI Easy to adopt new ones: DNS, mDNS, lmDNS etc.


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}


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


http://tinyurl.com/connectportx2

http://tinyurl.com/connectportx2

Case of study 1: XBee

I We developed a restricted middleware version using PythonI With more than 15 concurrent requests problems were

experienced


FoxG20 platform

I Processor: 400Mhz Atmel ARM9I RAM: 64MBI Platform version: Python 2.5I REST libraries: Python Std LibI Semantic libraries: Fuxi


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


All rights of images are reserved by theoriginal owners*, the rest of the content is licensed

under a Creative Commons by-sa 3.0 license.

* Kit (practicalowl), Stefan Paunovic, Amortize and Marco Crupi DigiInternational Inc. and Acme systems.

http://www.flickr.com/photos/practicalowl/433659667/

http://www.flickr.com/photos/stefanpaun/5324860794/

http://www.flickr.com/photos/amortize/527435776/

http://www.flickr.com/photos/marcocrupivisualartist/6916192386/

http://www.digi.com/products/wireless-routers-gateways/gateways/connectportx2gateways

http://www.digi.com/products/wireless-routers-gateways/gateways/connectportx2gateways

http://www.acmesystems.it/FOXG20