CONSISTENT MANAGEMENT OF CONTEXT INFORMATION IN

UBIQUITOUS SYSTEMS

Gabriel Guerrero-Contreras

José Luis Garrido

Carlos Rodríguez-Domínguez

Sara Balderas-Díaz

7th International Conference on Internet and Distributed Computing Systems

22nd September 2014

gjguerrero@ugr.es

jgarrido@ugr.es

carlosrodriguez@ugr.es

sarabd@correo.ugr.es

University of Granada Software Engineering Department

OUTLINE

1. Introduction

2. Consistent Management of Context Information

> The Service Entity and Replica Manager

> The Synchronization and Monitoring Services

> The Context Manager

3. Case Study

4. Conclusions and Future Work

G. Guerrero-Contreras et al. 2

1. INTRODUCTION (1)

• Context-aware systems use the context information to make decisions about their future behavior

• Ubiquitous environments make use of context-aware techniques to provide a natural and unconscious interaction with the computational system to the user

• Features of ubiquitous environment can affect to the consistency of distributed context information > Uneven conditioning, limited resources, dynamic network

topology, etc.

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1. INTRODUCTION (& 2)

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Support the synchronization and consistent management of distributed context information

Objective

• SOA, EDA and middleware technologies are not enough to support dynamic environments

• Existing approaches to manage context information follow a centralized scheme

• In context-aware systems it is decisive to maintain the correctness and the quality of context information

Motivation

2. CONSISTENT MANAGEMENT OF CONTEXT INFORMATION

• A model is proposed as a common basis for the management of shared resources

> It is based on the SOA model

> It provides two main services: Monitoring and Synchronization

• A Context Manager Service has been created from the specialization of the Synchronization service

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2.1 THE SERVICE ENTITY AND REPLICA MANAGER (1)

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2.1 THE SERVICE ENTITY AND REPLICA MANAGER (1)

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• The applications and services are considered Software Entities deployed in a device

• A service may be being accessed by one or more applications, and by one or more services (i.e., service composition)

2.1 THE SERVICE ENTITY AND REPLICA MANAGER (1)

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• A service can manage a kind of shared resources • Documents, images, database, etc.

2.1 THE SERVICE ENTITY AND REPLICA MANAGER (1)

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• Each service is made up of a Replica Manager • This avoid central controls and strengthen the system against

node disconnections and network partitions

2.1 THE SERVICE ENTITY AND REPLICA MANAGER (& 2)

• The Replica Manager is responsible of encapsulating the adaptation logic regarding the deployment of the services

> Providing a distributed solution to the dynamic deployment

> Improving the availability of shared resources (documents, images, etc.)

• The Replica Manager will need the information provided by the Context Manager Service

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2.2 THE SYNCHRONIZATION AND MONITORING SERVICES (1)

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2.2 THE SYNCHRONIZATION AND MONITORING SERVICES (1)

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• The Synchronization Service is an abstract service which must be specialized according to each particular resource to be synchronized

• It is based on the Monitoring Service

2.2 THE SYNCHRONIZATION AND MONITORING SERVICES (1)

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• The Monitoring Service is a basic service which stores all kind of information about changes on the different replicas of the shared resources

2.2 THE SYNCHRONIZATION AND MONITORING SERVICES (& 2)

• Thus a common basis for the consistent management of the shared resources is provided

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Synchronization service

The common part related to manage

the resource is identified and

assigned to the Synchronization

service

Specialization of the service

The particular requirements of a resource are implemented

in the specialization of the service

2.3 THE CONTEXT MANAGER (1)

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2.3 THE CONTEXT MANAGER (1)

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• The context information can be distributed and replicated

2.3 THE CONTEXT MANAGER (1)

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• Through the specialization of the Synchronization service, a Context Manager which can address these context inconsistencies at the service level is provided

2.3 THE CONTEXT MANAGER (& 2)

• The Context Manager will implement the ‘synchronize’ abstract method, where it will should add the specific synchronization algorithms for managing the context data resource.

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3. CASE STUDY

• In a hospital there is an Emergency service which form part of an ubiquitous environment

• The Emergency service will look for the most appropriate doctor to attend the emergency

• Different information need to be managed

> Location of the medical staff, availability of the medical resources, profile of the patients, etc.

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3. CASE STUDY

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The doctor is in the hospital

Context Manager Replica 1

Context Information

Emergency Service Monitoring

Service

3. CASE STUDY

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Context Manager Replica 1

Context Information

Emergency Service

The doctor is in the hospital

Context Manager Replica 2

Context Information

The doctor is in the ambulance

Monitoring Service

3. CASE STUDY

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Context Manager Replica 1

Context Information

Emergency Service

The doctor is in the hospital

Context Manager Replica 2

Context Information

The doctor is in the ambulance

Monitoring Service

3. CASE STUDY

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Context Manager Replica 1

Context Information

Emergency Service

The doctor is in the hospital

Context Manager Replica 2

Context Information

The doctor is in the ambulance

‘synchronize’

Monitoring Service

3. CASE STUDY

/**

* @param list: a list of events obtained from the `disjointSet' method

*/

void synchronize(List<Events> list){

foreach(Event evt in list){

evtName = evt.getMemberValue("object").GetString();

evtValue = evt.getMemberValue("value").GetString();

evtTime = evt.getMemberValue("timestamp").GetInt64();

[...]

if(this.getContextObject(evtName).getTimestamp() < evtTime){

this.setContextValue(evtName, evtValue);

}

[...]

}

}

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4. CONCLUSIONS

• The devised model provides to the software engineers the basis for a correct and consistent management of replicated/distributed resources

• From this basis a Context Manager has been provided

• The model is based on distributed scheme

• It also contemplates the adaptation logic of the replication of services at run-time

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4. FUTURE WORK

• Currently, a simulation on ns3 network simulator is under development. In order to perform a study the behavior of the Replica Manager component

• We plan to study the composition between the herein presented services and other high level self-adaptive services, such as a location service

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THANKS FOR YOUR ATTENTION!

QUESTIONS?

7th International Conference on Internet and Distributed Computing Systems

22nd September 2014

University of Granada Software Engineering Department