CAMPUS09 Pesentation Panagiotis Papakos

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VOLARE :ADAPTIVE WEB SERVICE DISCOVERY IN

MOBILE SYSTEMS

Panagiotis Papakos, David S Rosenblum,Licia Capra, Arun Mukhija

University College London

CAMPUS 2009

12/06/09


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Introduction

The VOLARE Middleware Solution

Example Scenario

Objectives and Novelties

Implementation and Evaluation

Conclusions

Project motivationOverview


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Project motivationntroductionBackground

Web Services are becoming increasingly popular.

Smartphones make more complex functionality feasible.

Extensive work on applications using web services in the mobile world.

The use of web services in the mobile environment presents uniquechallenges :

Resources are limited.

The contextof a mobile device, and therefore its requirements andcapabilities, constantly change during runtime.

An adaptive approach is required.


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Service Requesting

Typical Web Service broker based service discovery with a mobile device asa client

Problem

The web service requirements (QoS requirements, functionality etc) of amobile device may change due to changes in the context or the resources ofthe mobile device.

Context : Location, Speed, Other Local Devices, User Preferences etc.

Resources : Battery Level, Memory Usage, CPU load etc

Project motivation

Client DeviceService

RepositoryBroker

ServiceRequest

ServiceBinding

Query

Matching Services

Introduction


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Service Provision

Typical Web Service broker based service discovery with a mobile device asa service provider

Problem

The web service provider capabilities of a mobile device may changedepending on itsresources and context. This can lead to bottlenecking.

A method to adapt the web service requests and descriptions to reflect thecurrent needs and capabilities of a mobile device is needed.

Project motivation

ProviderDevice

ServiceRepository Broker

ServiceDescription

Query

Matching Services

Introduction


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Proposal

A middleware that :

Monitors the Resources of the Device.

Monitors the Context of the Device.

Dynamically adapts the web service Request appropriately.

Dynamically adapts the web service description of the provided servicesaccordingly.

Rebinds web services when old bindings no longer satisfy requirements.

Service Binding Matching ServicesMobileDevice Broker

AdaptedService Request QueryService Request

Context andResource data VOLAREMiddleware

Project motivationProject motivation


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Introduction


Example Scenario



Conclusions



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Prototype details

An adaptation policy language underdevelopment for VOLARE.

Adaptation policy files used to describe therelationships between context or resource

variables and QoS metrics in servicerequests/descriptions.

Service Descriptions and adaptation policiesseparate. This allows implementation of VOLAREwithout changing existing service descriptions.

Compatible with non-VOLARE serviceproviders/clients.

Allows adaptation of variables not included inthe service descriptions (i.e trust).

Project motivationThe VOLARE Middleware Solution


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Project motivationThe VOLARE Middleware Solution

Further Issues

Rebinding of Web Services

A method needs to be developed for evaluating when it is desirable torebind to another service.

On-the-fly deployment and unemployment of web services.

Balancing between Client and Providerfunctionalities, in the case of mobiledevices that act as both.

By altering the QoS levels offered or requested, the two functionalities

can be balanced according to the current needs of the device.


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Introduction


Example Scenario



Conclusions



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Project motivationExample Scenario

1. Normal OperationAs the vehicle drives around, the mobile device will :

Request traffic information so that it can plan the optimal route

Provide local traffic information to surrounding devices at a

certain refresh rate

2. Low TrafficWhen the vehicle enters a Low Traffic zone, its speed will increase. The

device will :

Increase the refresh rate it requires. The device must quickly acquireup-to-date surrounding traffic information, to quickly plot the optimal

route. since its location is rapidly changing.

Decrease the traffic information provided, to conserve resources for

receiving traffic updates and rapid route plotting.


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Project motivationExample Scenario

3. Heavy TrafficWhen the vehicle now enters a heavy traffic zone, its speed willdecrease. The device will :

Decrease the refresh rate it requires, to conserve resources.

Since the location changes slowly, there is not need for rapid

updates.

Increase the refresh rate it provides, since there are more

available resources, and it becomes more critical to update

incoming cars of its heavy traffic state, so they can avoid the

area.


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Project motivationExample ScenarioAdaptation Policy

For this example, the service description/request would also be attached

with an adaptation policy, specifying the relationships between context and

resource variables and the QoS metrics of the service description/request.

Battery, CPU,

NetworkAvaliability Date, Time, Location, Status bandwidth =bandwidth*NetworkAvaliabilityrefreshrate =refreshrate*(CPU+Battery)*1.5

refreshrate =refreshrate*(CPU+Battery)*0.5

TrafficServicewww.trafficServices.com/TrafficServiceTraffic Information 50 5 This Web servicetransmits the current

traffic status of the mobile devicewhen driving.


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Introduction


Example Scenario


Implementation and Future Issues

Conclusions



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VOLARE Novelties

No similar adaptation approaches currently applied on the realm ofmobile web service discovery.

This project will allow us to evaluate the effects of fully dynamic

adaptation in mobile web service discovery.

Very little existing work on adaptive web service providerfunctionality on mobile devices.

VOLARE can be used on existing web services without modifyingthem.

Project motivationObjectives and Novelties


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Introduction


Example Scenario



Conclusions



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ImplementationA series of two prototypes will be implemented to demonstrate the benefits of

adaptation in service discovery in mobile systems.

1. The first prototype under development is a proof-of-conceptimplementation, deployed on actual mobile device to prove the viability ofthe architecture.

2. The second prototype will be developed as a simulation to allow more

controlled evaluation of the effects of adaptation in service discovery.

EvaluationEvaluation after every prototype iteration, using :

Self developed case scenarios.

Simulation using context and resource usage datasets.

Variables evaluated :1. Discovery Speed

2. Discovery Accuracy

3. Resource Efficiency

Project motivationImplementation and Evaluation


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Introduction


Case Example



Conclusions



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Use of web services by mobile devices can be problematic,because requirements change according to changes in context andresources.

Service provider capabilities also change according to context andresources

The VOLARE middleware will adapt the service requests anddescriptions according the current condition on the mobile device.

Introducing dynamic adaptation in mobile web service discovery will

enable: More accurate service bindings.

More resource efficient SOAs.

More reliable service provision using mobile devices.

Project motivationConclusions


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Questions ?

Project motivationVOLARE

CAMPUS09 Pesentation Panagiotis Papakos

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