restful triple spaces of things

RESTful Triple Spaces of ThingsWoT 2012

Aitor Gomez-Goiri, Pablo Orduna, Diego Lopez-de-Ipina

DeustoTech - Deusto Institute of Technology, University of Deustohttp://www.morelab.deusto.es

June 19, 2012

http://www.morelab.deusto.es

Outline

Introduction

Otsopack

Evaluation

Conclusions

RESTful Triple Spaces of Things 2 / 42

Outline

Introduction

Otsopack

Evaluation

Conclusions

RESTful Triple Spaces of Things Introduction 3 / 42

The Web of Things

I Growing connectivity of everyday objects.I How to integrate them? What about using a web compliant

manner?I Scalable interaction, integration with the web world...I But also inherits problems from the web world!

I Lack of expressiveness and human orientation ⇒ TheSemantic Web

I The SW enables sharing knowledge across differentapplications


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 Space-based computingI time autonomyI space autonomyI reference autonomy

I Uses semantic web to describe knowledge shared betweenall the participant nodes

I 2 applications using standard ontologies can interact amongthem automatically enriching one each other.

I Requirements: they use the same space and standard andlinked ontologies.


Goal

I Adapt TSC to IoTI Fully distributed

I The objects or devices manage their own information.I Direct/Route their queries to others.I The participants form a “virtual space”.

I Through an HTTP API (a wide range of devices can be partof TS)


Outline

Introduction

OtsopackLayersTS HTTP API

Evaluation

Conclusions

RESTful Triple Spaces of Things Otsopack 8 / 42

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.


Otsopack TS API

The developers using ourmiddleware use writing andreading primitives.


Data access

To store knowledge and toreason over it.


Network layer

I Discover new nodesI Consume other nodes’

HTTP API


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


Outline

Introduction

Otsopack

EvaluationCase of study 1: XBeeCase of study 2: FoxG20Case of study 3: Tablet computerCase of study 4: regular computer

Conclusions

RESTful Triple Spaces of Things Evaluation 17 / 42

Goal

Prove the easy adoption of the proposed middleware by differentplatforms and its feasibility

⇓

3 different resource-constrained platforms(and a regular computer is also provided as a baseline for the comparison)


Reasoning

Which platforms could be able of reasoning over their data?⇓

RDFS reasoning evaluation⇓

we used real examples from the SSN ontology⇓

1. Data structure (TBox)2. Different measures (ABox)


XBee gateway platform

I ConnectPort R© X2 (XBee to IP gateway)I RAM: 8MBI Platform version: Python 2.4I REST libraries: Python Std LibI Semantic libraries: None


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


Samsung Galaxy Tab

I Processor: 1 GHz Cortex-A8I RAM: 512MBI Platform version: Android 2.2I REST libraries: Python Std LibI Semantic libraries: Sesame 2.4.2


Case of study 3: Tablet computer

I Android implementation usedI HTTP request are handled worse than FoxG20

(remember it was a reduced version)I Reasoning was halfway between the FoxG20, but yet far

enough from the regular computerI x6 TBox and x5 ABox


My Toshiba laptop

I Processor: 2.26 GHz Intel Core 2 DuoI RAM: 4GBI Platform version: Java SE 6.0I REST libraries: RestletI Semantic libraries: Sesame 2.6.4


Case of study 4: regular computer

The time needed by any reasoning engine to reason requiresmuch less time than with any other device

⇓

This stresses the open challenge it represents to reason inresource constrained devices


Outline

Introduction

Otsopack

Evaluation

Conclusions

RESTful Triple Spaces of Things Conclusions 28 / 42

Conclusions

I We use RESTful interface in our middleware as the key forbuilding a fully distributed space

I Doing so, we ease the adoption of this API in heterogeneousand constrained devices

I Lessons learnt:I For small scenarios using semantic may seem complex

I The richer descriptions are beneficial in the long term whenmore and more applications share and exploit their knowledgein spaces

I The developer does not have to worry about accessing todifferent devices, instead he cares about the data shared inthe conceptual space

I Still, each device can be seen as a browsable WoT devicewhich serves semantic content


Bibliography

World Wide Web Consortium.W3c semantic web faq, August 2011.

RESTful Triple Spaces of Things Bibliography 31 / 42

RESTful Triple Spaces of Things Backup slides 32 / 42

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;


Dissemination strategies

The technique known as negative broadcasting is implementedI all write operations are executed locallyI all read and query operations are propagated to the rest of

the nodes belonging to the same space(but we are working on other strategies)


Discovery

I Registry based discoveryI Multicast based implementedI Easy to adopt new ones: DNS, mDNS, 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}


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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