AUTONOMOUS FILE SHARING FOR SMART ENVIRONMENTS

Jussi Kiljander, Matti Eteläperä, Janne Takalo-Mattila, Juha-Pekka Soininen

VTT Technical Research Centre of Finland, Kaitoväylä 1, Oulu, Finland

Kari Keinänen

VTT Technical Research Centre of Finland, Vuoriniementie 3, Espoo, Finland

Keywords: Smart Environment, Smart-M3, File Transfer, Semantic Interoperability, Ontology.

Abstract: Smart Environment is a physical place where different kinds of devices interact meaningfully with each

other to assist and support us in our everyday life. A key requirement for enabling these kinds of smart

systems in physical spaces is the ability to share files autonomously between various devices in the

environment. In this paper a novel solution for autonomous file sharing between heterogeneous devices is

presented. Here autonomous means that the devices interact with each other seamlessly and the

heterogeneity of devices and services providing file sharing is hidden from the end user. Our approach is

based on presenting information about the files and file sharing protocols by using ontologies and we utilize

Smart-M3 as the platform for sharing semantic information between devices in a physical space. To

demonstrate our approach for autonomous file sharing in practice we have implemented a meeting

application to various mobile platforms.

1 INTRODUCTION

Our environment is full of heterogeneous electronic

devices such as computers, mobile phones and home

appliances, for example. Pervasive and Ubiquitous

Computing are computing paradigms aiming to

enable Smart Environments where these devices

interact meaningfully with each other in order to

provide useful services for people in the

environment (Weiser, 1991). Files are a significant

part of persistent storage in modern computer

systems and file sharing is an integral part of many

inter-device applications. These applications include

the Web and email, for example. It is also apparent

that many Smart Environment applications would

require devices to share files such as videos, music,

images, documents and even software with each

other. File sharing is therefore also an important part

of interaction between ubiquitous devices and a

common solution for file sharing in Smart

Environment is needed.

A typical scenario of file transfer in Smart

Environment can be divided into two parts:

discovery of file sharing services and execution of a

selected functionality of the service. The discovery

functionality is usually provided by some Service

Oriented Architecture (SOA) solution such as

Universal Plug and Play (UPnP), Web Services or

Common Object Request Broker Architecture

(CORBA), for example (UPnP forum, 2008), (W3C,

2002), (OMG, 2002). Also other non-SOA solution

for service discovery exist e.g. Bluetooth Service

Discovery Profile (SDP) and the Zeroconf standard

(Cheshire and Steinberg, 2005).

In addition to discovering the file services, a

device must be able to interact with the services to

execute specific file transfer functionality such as to

store, modify or request a file, for example. For this

purpose many standard file sharing protocols based

on the traditional client/server paradigm exists.

These protocols include the File Transfer Protocol

(FTP), Secure Copy (SCP) and Apple Filing

Protocol (AFP), just to name a few. Additionally

numerous SOA solutions have their own methods

for describing services that provide file sharing

capabilities. As an example UPnP requires a priori

standardization of the service interfaces were as the

Web Services and CORBA, for example, utilize

technologies such as Web Service Description

Language (WSDL) and Interface Definition

191

Kiljander J., Eteläperä M., Takalo-Mattila J., Soininen J. and Keinänen K..

AUTONOMOUS FILE SHARING FOR SMART ENVIRONMENTS.

DOI: 10.5220/0003362501910196

In Proceedings of the 1st International Conference on Pervasive and Embedded Computing and Communication Systems (PECCS-2011), pages

191-196

ISBN: 978-989-8425-48-5

 2011 SCITEPRESS (Science and Technology Publications, Lda.)

language (IDL) for describing the service interfaces

in a machine interpretable format.

As can be seen there are many service solutions

and protocols available that provide file sharing

capabilities for devices. In addition the variety of

communication technologies such as the ZigBee,

Bluetooth and Wireless Local Area Network

(WLAN) creates their own challenges for

autonomous file sharing in Smart Environments.

With a large amount of different communication

technologies, file sharing technologies and SOA-

based file sharing services it can be a difficult both

to find all available file transfer services and to

interact with the services to perform the required

operation. Basically this requires that each device

sharing a file must use all discovery mechanisms it

supports for finding the available file services and

then publish the file to each service it is capable to

interact with. Additionally to interoperate with

devices that do not utilize SOA solutions the devices

are also required to advertise the file with each

communication technology it supports. It is apparent

that this creates a lot of overhead both to the code

size of applications and to the communication

between the devices.

In this paper we propose a novel solution for

autonomous file sharing with heterogeneous devices,

file transfer methods and SOA solutions by utilizing

an interoperability platform called Smart-M3 on top

of these existing solutions. As presented by (Liuha,

Soininen, Otaloea, 2010) the Smart-M3 achieves

semantic interoperability between devices of Smart

Environments by providing architecture for utilizing

ontology-based information presentation in a

physical space context. In our approach we present a

common ontology for defining information about the

available files, file transfer protocols and file

services in semantic form and publish this

information available to all devices in the Smart

Environment. This enables devices sharing the

common ontology to negotiate about the possible

solutions for file sharing and then select the

appropriate method for transferring the file.

2 SMART-M3

Smart-M3 is an independent information level

interoperability architecture that can be implemented

on top of any communication or service level

solution. The fundamental idea of Smart-M3 is to

utilize the Semantic Web ideas of ontologies and

semantic interoperability in a physical space context

(Berners-Lee, Hendler, Lassila, 2001). In addition to

the ontology-based interoperability model Smart-M3

defines a functional architecture that specifies the

methods for accessing the semantic information in a

physical space. The Smart-M3 functional

architecture consists of Knowledge Processors (KP)

and Semantic Information Brokers (SIB). Fig. 1

presents the Smart-M3 concept including the core

elements and their relations.

Figure 1: Smart-M3 Functional Architecture.

The Smart-M3 functional architecture is based

on publish/subscribe paradigm and therefore it

enables reactive event-based communication

between KP and SIB entities. SIB is the information

repository of the Smart Space and it provides

operations for modifying and requesting the

semantic information. KPs form the actual

application for the end user by utilizing the SIB

service for sharing semantic information with each

other. In order to hide the complexity of both

information presentation and communication from

the application logic, the KP is divided into KP

Interface (KPI) and use case logic parts. KPs that

interact with each other via SIB are interoperable if

they have a common ontology that specifies the

concepts and relationships between the concepts in a

given domain.

Smart Space Access Protocol (SSAP) is the

communication protocol of Smart-M3 and it defines

the rules and syntax of operations for accessing the

semantic information in the SIB. The SSAP

specifies operations such as insert, remove and

update for modifying the semantic information as

well as various formats of query and subscribe

operations. To ensure that the content of the SIB

does not change during the execution of any

operation each SSAP transaction is executed in an

atomic fashion. In addition to these operations the

SSAP contains join and leave operations that are

used to provide access control and authentication.

The information access and security in Smart-M3-

based systems is further described in (Suomalainen,

Hyttinen and Tarvainen, 2010).

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In Smart-M3 the Resource Description

Framework (RDF) and RDF-Schema (RDFS)

technologies are the backbone of the ontology-based

interoperability model (W3C, 2004). RDF is a

family of W3C specifications for modelling

metadata in form of subject, predicate and object

triples. Because RDF triples are similar to basic

sentences of a human language, it is a natural way to

make statements about information with certain

properties and relationships. RDFS is an extensible

knowledge presentation language that defines

vocabularies for building simple ontologies using

RDF. The current reference implementation of the

SIB provides three languages for querying (and

subscribing to) the RDF data: Triple, SPARQL and

Wilbur Query Language (WQL) (W3C, 2008),

(Lassila, 2002).

3 APPROACH FOR

AUTONOMOUS FILE

SHARING WITH SMART-M3

In our approach we divide the challenge for

autonomous file sharing into three distinct levels:

communication, service and information level. Fig. 2

presents a logical view of our approach.

Figure 2: Logical view of approach for autonomous file

sharing in Smart Environments.

The communication level covers the Open

System Interconnection (OSI) model layers from L1

to L4. It provides the basic functionality required for

transmitting bytes of data between devices.

The role of the service level is to provide

technologies for devices to share services with each

other. The Service level covers existing SOA

solutions and protocols. In the file sharing context

these protocols include the FTP, SCP, Bluetooth’s

File Transfer Profile and BitTorrent, for example. In

addition there are SOA solution such as UPnP, Web

Services, OSGi and NoTA that have their own

services for providing file transfer capabilities

(OSGi Alliance, 2005), (NoTA World, 2007).

Information level is the highest level in our

approach. The role of the information level is to

make information of devices available and the

semantics of the information interpretable for other

devices in the environment. We propose Smart-M3

to be used in the information level for sharing

semantic information required in the file sharing

context.

In our approach necessary information about

files, transfer protocols and services is modelled as a

common ontology and the SIB is used as a common

search extent of this semantic information. This way

the devices are able to discover the available files in

a given environment and then select the most

appropriate file transfer technology for transferring

the file between devices.

We utilize RDFS vocabulary as the ontology

language in our approach. This is because the

current implementation of the SIB with WQL

supports RDFS level reasoning (also the

owl:sameAs and owl:InverseFunctionalProperty

features of the Web Ontology Language (OWL) are

supported) so the RDFS is the most practical choice.

Fig. 3 illustrates the ontology of our approach.

Figure 3: File Sharing Ontology.

The File class is the base class for all files. It

contains basic properties describing the name,

format, size (in bytes) and modification date of the

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193

file. The ImageFile and TextFile are example

subclasses of the File class that can be used to

describe the type of the file more specifically. It is of

course possible to introduce new subclasses for the

File class and for these subclasses as well. The

FileService class is the class for all file transfer

services. The ServiceInterface class specifies the

interface of services. This is done through the

ServiceFunction and FunctionParamater classes. In

addition to accessing files through SOA services, we

also developed an elegant way to request files by

interacting only on the semantic level. For this

purpose the FileRequest and SharingProtocol classes

have been defined. FileRequest class presents a

request to a file in the SIB and it has two properties.

The hasTargetFile property defines the file (instance

of the File class) to be requested and the

hasSharingProtocol property specifies the protocols

supported by the requester. SharingProtocol class is

a base class for all various protocols enabling file

sharing. The Fig. 3 also illustrates several example

subclasses for the SharingProtocol class and it is

possible to introduce new subclasses when

necessary.

To achieve autonomous file sharing on the

semantic level a KP has to be both be able to

subscribe to all the available files and all file

requests to the files the KP has published into the

SIB. This way the KP will be informed when new

file has been published or a file request to his file

has been made. Because WQL hides the RDFS

reasoning from the application developer it is

practical to use WQL when performing these

operations. An abstract syntax for Wilbur value

subscription can be presented in the following way:

R = S

(n, path) (1)

where S

WQL

is the WQL subscription operation,

R denotes the result nodes, n is the start node of the

subscription and path specifies the labels

(predicates) to be traversed from the start node in the

RDF-graph. The WQL subscription that returns all

available files can be now presented as:

R = S

(File, inv(rdf:type)) (2)

where File is the URI of the File class, inv() is a

WQL specific operations that requires the path

defined by the subexpression e to be traversed in a

reverse direction and rdf:type is a RDF property

denoting that resource is an instance of a Class.

With WQL it is also possible to perform a single

subscription that returns all instances of the

SharingProtocol class and its subclasses that are

connected to the given file via hasSharingProtocol

and hasTargetFile properties. The WQL subscription

that returns all SharingProtocol instances when a

new file request is inserted to the SIB can be

presented as:

R = S

WQL

file

, seq(inv(‘hasTargetFile’),

‘hasSharingProtocol’))

(3)

where n

file

is the instance of the File class and

both seq() and inv() are WQL specific operations.

The operation seq(e

,…e

) traverses a sequence of n

steps of subexpressions e

,…,e

. Fig. 4 illustrates

how the queries presented in (2) and (3) traverse

through a simplified RDF-graph and return all File

and SharingProtocol instance.

Figure 4: WQL value subscriptions to the instances of

SharingProtocol and File classes.

To concretize our approach a scenario that

describes how utilizing semantic interoperability

enables autonomous file sharing between devices in

a Smart Environment is presented next. In the

beginning of the scenario there is a Web Service

with FTP server capabilities available and

information about this service is presented in the

SIB. Now a device that is capable of communicating

with the service can discover it and then store a file

and publish information about the file into the SIB.

Another device that has subscribed to all the files in

the SIB will now get an indication that a new file is

available. Let’s then say that the device would need

this file but is unable to interact with Web Services

because it supports only bluetooth for transferring

files. Without the semantic interoperability the

device would not even know that there is this kind of

file available. However, now a KP in the device can

publish information (along the common ontology in

Fig. 3) that it wants to request this file. The devices

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that have this file will get notification from the SIB

that the file request has been made. If either of the

two devices support bluetooth based file transfer

they can now send the file to the bluetooth address

specified by the requester.

4 IMPLEMENTATION

In order to demonstrate our approach for

autonomous file sharing in practice we have

implemented a meeting application for several

heterogeneous mobile platforms. These mobile

platforms include N900, N97, iPhone and Nexus

One. TCP/IP over Wireless Local Area Network

(WLAN) is used as the communication solution and

Zeroconf protocol provides the SIB discovery in the

WLAN. Fig. 5 presents how the mobile devices used

in the demonstration interact with each other via the

SIB.

Figure 5: Meeting demonstration set-up.

In addition to the file sharing ontology presented

in the section 3 two other classes have been

specified for the ontology used in the meeting

application. Meeting class presents the available

meetings in the Smart Environment and it has three

properties. The “hasName” property defines the

display name of the meeting. The “hasParticipant”

property specifies the participants of a given

instance of the Meeting class and the “hasFile”

property defines the available files in the given

meeting. Participant class represents contact

information of meeting participants. The “hasName”

and “hasPhoneNumber” properties present the name

and phone number of the participant respectively.

Fig. 6 illustrates the Meeting ontology classes and

their relations.

Figure 6: Meeting ontology for file and contact sharing.

With this simple ontology we have created a

meeting application where users can create and

participate to meetings and share their contact

information and files with each other. By

introducing new properties for ImageFile and

TextFile classes we have also demonstrated how

easy it is to create new features to applications by

mashing-up existing information. An example

scenario of the interaction between meeting KPs and

the SIB is presented next.

Let’s say that a participant of a meeting

publishes a scientific article to the meeting through

his KP and defines himself as the author the paper.

Another user subscribed to all the files of the

meeting via his KP will now be get indication that a

file has been published. The second participant is

interested in the article published by the first

participant and makes a request to the file into the

SIB. Now the KP in the first participant’s device

receives indication from the SIB and sends the file

using the file transfer capabilities the receiving KP

has. In this case plain TCP/IP was used to stream the

file data between devices.

A new feature to this application can be

developed by utilizing the properties defined for

ImageFile and TextFile classes. By performing a

WQL subscription to authors of the file the KP of

the second user can be informed when additional

information about the author is available. Let’s say a

third person now decides to take a picture of the

author and publishes this picture with the metadata

specifying that the author is in the picture into the

SIB. Assuming there is also contact information of

the first participant available the KP in the second

participant’s device can now autonomously request

the picture and inform the user that there is

additional information about the author available.

The third user can now contact the possibly

unknown author if he wants to discuss about the

AUTONOMOUS FILE SHARING FOR SMART ENVIRONMENTS

195

article. Fig. 7 illustrates the interaction between KPs

and the SIB in the presented scenario.

Figure 7: Sequence diagram illustrating the interaction

between KPs and the SIB.

5 CONCLUSIONS AND FUTURE

WORK

This paper presented a novel approach for

autonomous file sharing in Smart Environments. The

fundamental idea of the approach was based on

utilizing semantic interoperability platform called

Smart-M3 in file sharing context. Necessary

information about files, file transfer protocols and

file services was modeled using ontology and a

novel solution for negotiating about the possible file

sharing methods was presented. The approach was

demonstrated by implementing a meeting

application for heterogeneous mobile platforms from

various vendors. The meeting application also

illustrated the flexibility and expandability

advantages of the ontology-based information

presentations approach to create new applications

and features by mashing-up existing information.

The paper also presented how describing

information about the content of files can take the

autonomous file transfer to the next level. However,

we only scratched the surface by defining the

authors of text files and objects of images. The next

step to be done is to describe the contents of files

more specifically. This way the KPs could

automatically make more advanced searches to the

files based on the context and user preferences.

ACKNOWLEDGEMENTS

This work has been funded by the Device and

Interoperable Ecosystem (DIEM) and Open

Ubiquitous Technology (OPUTE) projects.

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