A QOS-BROKER-BASED FRAMEWORK FOR PERSONALIZED

WEB SERVICES PROVISIONING TO MOBILE USERS

Elarbi Badidi

, Larbi Esmahi

, M. Adel Serhani

and Ikbal Taleb

College of Information Technology, United Arab Emirates University, PO.Box. 17551, Al-Ain, United Arab Emirates

School for Computing & Information Systems, Athabasca University

1 University Drive, Athabasca, Alberta, T9S 3A3, Canada

Keywords: Service oriented computing, Mobile workers, Tailored services provisioning, Quality of service.

Abstract: This paper proposes a broker-based Web services provisioning system for mobile users with QoS

requirements. It describes a set of cooperative brokers distributed over different sites that work together to

provide personalized services for mobile users while they move from one location to another in their

corporate and partners’ networks. Access to QoS-enabled Web services is obtained in accordance with the

users’ home policies. This is made possible by negotiating the user profile and the terms of the service level

agreement.

1 INTRODUCTION

With the advent of service oriented computing and

the prevalent deployment of business applications on

the web to reach a large base of customers, many

organizations have moved their business online.

Web Services are the current most promising

technology based on the idea of service oriented

computing. They provide the basis for the

development and execution of business processes

that are distributed over the network and available

via standard interfaces and protocols.

Another development in the area of service

oriented computing is the unprecedented rise in the

number of mobile workers using a variety of

handheld devices such as PDAs and SmartPhones to

consume online services. Modern mobile devices are

often fully equipped with broad capabilities. Most of

them support several wireless communication

options including Wi-Fi, Bluethooth, GPRS, and

EDGE. They also come with advanced multimedia

capabilities including streaming. These devices

present now browsing capabilities that go beyond

the simple WAP protocol. Mobile computing

extends the e-business infrastructure to new classes

of devices, delivering on-demand information

wherever it is needed, using any device. With the

proliferation of mobile devices, wireless business

applications, i.e. messaging and voice services, are

more and more developed and deployed using Web

services. These services offer the possibility to

overcome the limitations of individual mobile

devices by making functionality offered by others

available to them on an as-needed basis. Thus, using

the service-oriented computing paradigm in mobile

environments will considerably enlarge the variety

of accessible applications and will enable new

business opportunities in the mobile space by

delivering integrated functionalities across wireless

networks.

Mobile workers are increasingly requiring

services tailored to their needs as they move from

one location to another in their corporate and

partners’ networks. They are also requiring retaining

access to their corporate services as they move to

new locations. In this paper, we describe our broker-

based framework, which aims to offer a working

environment that allows mobile users to use home

services as they move to new locations in their

corporate or partners' networks.

2 RELATED WORK

Our work is motivated by the desire to provide

mobile workers with local services tailored to their

147

Badidi E., Esmahi L., Adel Serhani M. and Taleb I. (2009).

A QOS-BROKER-BASED FRAMEWORK FOR PERSONALIZED WEB SERVICES PROVISIONING TO MOBILE USERS.

In Proceedings of the International Conference on Wireless Information Networks and Systems, pages 147-152

DOI: 10.5220/0002232101470152

 SciTePress

needs and to their home-profiles as they move from

one location to another in their corporate or partners’

networks. To achieve this, two main aspects need to

be considered. First, we need to identify the mobile

worker’s device in use at any particular time and its

capabilities as well as his/her preferences and

functional and non-functional service requirements,

such as the minimum level of QoS they are willing

to accept. Second, a close cooperation between the

home location and the visited one needs to be

established to negotiate and agree on issues related

to the user’s profile.

Several research works have studied the issue of

service delivery to mobile users. The authors in

(Ganna, 2003) proposed a policy-based service

provisioning and users management using mobile

agents. Their architecture is based on the notion of a

domain that represents an administrative authority

with its own behavior, policies, and users. Harroud

et al. describe an agent-based service provisioning

system for mobile users (Harroud, 2003). The

system comprises a set of cooperative agents

distributed over different sites that work together to

provide personalized services for mobile users over

the Internet. An Adaptive Service Presentation agent

is used to adapt the service presentation to the

capabilities of the users' mobile device. The work of

Riva describes a two-tier model for providing

services to mobile users (Riva, 2007). The model

presupposes that the system is aware about the

users’ profiles and context as well as available

services and has capabilities to match these with

each other. The authors in (Nor Azhan, 2007)

proposed a service-based content adaptation

platform, which adapts content for display on mobile

device without user intervention.

These works share some common goals with our

proposed work. However, they were done in other

contexts other done the service-oriented

environment, which currently represents the most-

predominant environment for service delivery. Our

work takes advantage of the various standards that

have been developed in the last few years for both

Web services and mobile computing especially the

standards for describing the mobile device

capabilities.

3 SERVICES ON MOBILE

DEVICES

Several service providers currently offer services

that allow information to be pushed to a mobile

device, or offered via a limited Web-browser

interface. With a service-oriented architecture, it is

becoming possible to offer services that fully use the

power of the mobile device.

Nevertheless, mobile services access is still

suffering today from interoperability and usability

problems. This is to some extent attributable to the

small physical size of the screens of mobile devices.

It is also partly due to the incompatibility of many

mobile devices with not only computer operating

systems, but also the format of much of the

information that is delivered to mobile devices.

The W3C Mobile Web Initiative (MWI) is a new

initiative established by the W3C to develop best

practices and technologies for creating mobile-

friendly content and applications. The goal of the

initiative is to enable the access to the Web from

mobile devices and to make it more reliable and

accessible. This typically requires the adaptation of

Web content based on the device capabilities. The

W3C has published guidelines (Best Practices, W3C

mobileOK checker service) for mobile content

(W3C, ). The MWI Device Description Working

Group is actively tackling the problem of device

diversity by setting up a repository of device

descriptions (W3C Mobile Web Initiative). Authors

of Web content may use the repository to adapt their

content to best suit the requesting device.

The OMA (Open Mobile Alliance) specification

defines the User Agent Profile (UAProf) to describe

capability and preference information of wireless

mobile devices (Open Mobile Alliance, 2001). This

information is to be used mainly by content

providers to generate content in a suitable format for

the specific device. It is based on the generic

framework W3C CC/PP (Composite Capabilities/

Preference Profiles) (W3C, 2007). CC/PP deﬁnes a

schema for the description of a device’s profile,

which is composed of components that describe

characteristics of hardware, software, network, and

so on. A CC/PP profile can be used to adapt Web

contents to a speciﬁc device. A UAProf file

describes the capabilities of a mobile handset,

including Vendor, Model, Screen size, Multimedia

Capabilities, Character Set support, and more.

4 SERVICE PROVISIONING

FRAMEWORK

4.1 Service Provisioning Requirements

To provide mobile workers with tailored services as

WINSYS 2009 - International Conference on Wireless Information Networks and Systems

148

Figure 1: Framework components.

they move from one location to another in their

corporate networks or their partners’ networks,

several issues need to be addressed.

Authentication and authorization control to

identify the user and his/her authorized services

on the home site.

Identification of the mobile user devices, so that

the service presentation will be tailored to the

capabilities of these devices.

Exchange of the user profile between the home

site and the visited site to allow for identifying

the user preferences, and providing access to

local services using these preferences.

QoS monitoring and management so that the user

will be provided with his/her required and

authorized QoS.

4.2 Framework Components

To address these issues, our proposed framework is

based on a brokerage service to mediate on one hand

between the mobile user home site and the visited

site, and on the other hand between the mobile user

and local Web services on the visited site. The above

issues are handled by the broker components.

Another key component of the framework is the

Policy Manager, which is responsible for

maintaining authentication and authorization

policies, as well as polices for monitoring services

and their quality of service.

Figure 1 depicts the main components of the

framework at a given site. These components

cooperate to deliver personalized services to mobile

users with various devices across interacting sites.

They are under the control of the Coordinator

component and allow carrying out several

management operations: Admission control, QoS

negotiation, QoS-based service selection, QoS

monitoring, User profile management, and policies

management. The backend databases maintain

information about policies, user profiles and

preferences, and dynamic QoS information.

4.2.1 QoS Specification

Specification of QoS that providers can deliver may

be performed by incorporating QoS parameters, such

as response time, throughput and cost, into the

WSDL service description. This is the QoS model

supported by the UDDIe (Shaikh Ali, 2003). Other

works (Zuquim, 2006) (Ganna, 2003) have proposed

extensions to the Web services Policy Framework

(WS-Policy) to represent QoS policies of Web

services. WS_Policy does not specify how policies

are discovered or attached to a Web service. The

WS_PolicyAttachment specification (W3C, 2006)

defines such mechanisms.

In our framework, QoS policies are also stored in

the policies repository as well as the other policies

A QOS-BROKER-BASED FRAMEWORK FOR PERSONALIZED WEB SERVICES PROVISIONING TO MOBILE

USERS

149

concerning authentication, authorization, user profile

and preferences management, and mobile devices

profile management.Admission Control

The Admission Manager classifies incoming

requests and verifies the provisioned classes of QoS.

It is responsible of determining whether the received

requests are allowed to use the requested services.

This means that Web services access is denied to

requests from users who did not negotiate the level of

QoS with the selected Web services providers.

4.2.2 QoS-based Service Selection

The Request Dispatcher is in charge of implementing

different policies for the selection of an appropriate

web service that will deliver the user required service

with the required QoS. It performs the match-making

of required QoS with stored QoS. Various policies

have been specified in the literature regarding service

selection policies.

4.2.3 QoS Negotiation

The QoS negotiation process is carried out by the

QoS Negotiator in order to reach a service level

agreement (SLA) concerning the QoS to be delivered

to the user. The SLA specifies the service to be

provided by the provider to the client, the guaranteed

QoS, the cost of the service, and the actions to be

taken when there is a violation of the agreed QoS.

The negotiation protocol is detailed in next section.

4.2.4 QoS Monitoring

QoS monitoring is carried out by the QoS Monitoring

Manager and by the Web Service Controller (Figure

1). The QoS Monitoring Manager continually

observes the level of QoS level rendered to clients.

QoS parameters, such as response time and

availability that need to be observed are specified in

the contract. Observation is achieved through

periodic measurement of these QoS parameters at

some observation points at the server side and at the

client side. QoS violation is detected when the

measured value of a QoS parameter does not meet

the requirements of the agreed one.

4.2.5 Profile Management

The Profile Manager is responsible for managing

users’ profiles, which include their preferences, in

terms of personalized services, current location, and

required QoS. It is also responsible for negotiating

the user profile and authorized services at the visited

site, as well as the devices profiles, that are described

using UAProf and CC/PP. Profile negotiation is

detailed in next section.

4.2.6 Policies Management

Utilization of policies in Web services environments

has been recognized since the specification of the

first standards for Web services. In the WS-Policy

specification (Bajaj, 2007), individual requirements

or capabilities of a policy subject are declared using

XML policy assertion elements. Policy assertions are

the building blocks of policies. Each assertion

describes an atomic aspect of a service's

requirements (e.g. authentication scheme,

authorization scheme, QoS/SLA characteristics, etc.).

A policy expression can be comprised of one or more

policy assertions assembled in Policy alternatives

using logical policy operators. This expression can

also be associated with a Web service resource, such

as a service or endpoint, using WSDL or other

mechanisms defined in WS-PolicyAttachment (W3C,

2006).

The Policy Manager is responsible for

maintaining authorization policies, and polices for

monitoring services and quality of service. It receives

access control requests, processes them against a set

of policies that define how the services are to be used

by its mobile users, and returns access control

responses. Figure 2 depicts the architecture of the

Policy Manager. The Policy Decision Point (PDP) is

the component that grants or denies access to

services. It encompasses a rule engine that

determines the policies to apply when a user requests

access to a service. When a user attempts to access a

service with QoS requirements, the Policy

Enforcement Point (PEP) component sends a

message to the PDP asking whether to approve the

user request. It then replies with permission or denial

of access to that service based on the rules that have

been defined and the request parameters.

Figure 2: Policy Manager components.

WINSYS 2009 - International Conference on Wireless Information Networks and Systems

150

Figure 3: Inter-site profile negotiation.

5 INTER-SITE NEGOTIATION

5.1 Profile Negotiation

Figure 3 depicts the interactions between the brokers

at the visited site and the home site, to create a user’s

profile at the visited site.

The mobile user submits a request, including the

CC/PP profile of the mobile device in use, at the

visited site.

After processing the user’s authentication on an

authorized device, the Coordinator at the visited

site requests the user’s profile from its User

Profile Manager. If the user profile is available

locally, then the Coordinator starts negotiating

the terms of service with the mobile user as

described in the next section. Otherwise, the

following steps are accomplished.

A request is sent to the Coordinator at the home

site of the mobile user in order to get his profile.

This is achieved through the following steps.

The Coordinator at the home site of the mobile

user forwards the user profile request to its User

Profile Manager.

The home User Profile Manager reads the mobile

user profile from the profiles database.

The home User Profile Manager requests from

the home Policy Manager the policies regarding

the user, such as authorization policies to services

available at other sites to which the user may

have access and the type of access.

The home Policy Manager reads the policies

regarding the mobile user from the policies

database.

The home User Profile Manager returns the

requested profile of the mobile user to its

Coordinator.

The home Coordinator returns the user profile to

its peer at the visited site. After getting the final

profile of the user, the Coordinator at the visited

site starts negotiating the terms of the service

level agreement as described in the next section.

5.2 Policy-driven SLA Negotiation

Process

Once the user profile has been determined, the

mobile user and the QoS broker at the visited site

start negotiating the terms of the SLA according to

the following protocol (Figure 4):

1. The mobile user formulates a SLA request

detailing service provisioning request and sends it

to the Coordinator component at the visited site.

2. The Coordinator may decide whether the SLA

proposal can be processed. This decision is based

on the mobile user profile, determined in the

previous process. If for instance the requested

service is not among the services that are

authorized for the user, then a rejection is sent to

the user.

3. The Coordinator requests then the selection of a

target Web service from the Request Dispatcher.

A QOS-BROKER-BASED FRAMEWORK FOR PERSONALIZED WEB SERVICES PROVISIONING TO MOBILE

USERS

151

Figure 4: SLA negotiation protocol.

4. The Coordinator sends the SLA proposal and the

reference of the selected Web service to the

Policy Manager to decide whether the mobile

user request can be processed or not. This

decision is based on the requested level of service

and the Web service policies.

5. The Coordinator and the mobile user start then

negotiating the specific terms of the service

provisioning based on SLA requirements and

Web service policies. The Coordinator requests

from the QoS Negotiator to determine the final

profile by negotiating the level of QoS to be

delivered.

6. Proposals are returned to the mobile user, who

can accept or reject offers – rejections typically

trigger renegotiation.

6 CONCLUSIONS

In this paper, we have presented a cooperative

broker-based Web services provisioning system for

mobile users with QoS requirements. Policies are a

crucial part of the framework. They are used at

different levels: authorization, QoS specification,

QoS service monitoring, and description of service

policies. QoS brokers at the visited site and the home

site are involved in determining the mobile user

profile and in negotiating a final Service Level

Agreement. This final SLA details the terms of

service at the visited site according to several

policies: WS policies, selection policies, and QoS

policies.

A prototype of our proposed framework is under

development. The implementation platform includes:

NetBeans 6.5, the UDDIe registry, MySQL, and

Apache Neethi, which provides a general framework

for developers to use WS-Policy. As a future work,

we intend to extend our proposed architecture with

security policies using standards such as

WS_Security and WS_Policy.

REFERENCES

Bajaj, S., et al., 2007. Web services policy 1.5 –

framework. W3C Candidate Recommendation 28

February 2007. http://www.w3.org/TR/2007/CR-ws-

policy-20070228/

Ganna, M., Horlait, E., 2003. Policy-based service

provisioning and users' management using mobile

agents. Lecture Notes in Computer Science Vol. 2881

Springer 2003, ISBN 3-540-20298-6, pp. 53-66.

Harroud, H., Karmouch, A.M., 2003. A. Policy-driven

personalized multimedia services for mobile users.

IEEE Transactions on Mobile Computing, Vol. 2, Issue

1, Jan.-March 2003, pp: 16 – 24.

Nor Azhan, N., Wong, H.S., Khairil, I.B.G., Tamrin, M.,

2007. Using service-based content adaptation platform

to enhance mobile user experience. In Mobility'07, the

4th international conference on mobile technology,

applications, and systems.

Open Mobile Alliance, 2001. WAG UAProf, version 20-

Oct-2001.

http://www.openmobilealliance.org/tech/affiliates/wap/

wap-248-uaprof-20011020-a.pdf

Riva, O., Toivonen, S., 2007. The DYNAMOS approach to

support context-aware service provisioning in mobile

environments. Journal of Systems and Software, Vol.

80, Issue 12, 2007, pp. 1956-1972

Shaikh Ali, A., Rana, O.F., Al-Ali, R., Walker, D.W.,

2003. UDDIe: an extended Registry for Web services.

In SAINT 2003, the IEEE Symposium on Applications

and the Internet Workshops, pp. 85 - 89.

W3C,. W3C mobileOK Checker [Beta]. http://validator.

w3.org/mobile/

W3C, 2006. Web services policy attachment. http://www.

w3.org/Submission/WS-PolicyAttachment".

W3C, 2007. Composite Capability/Preference Profiles

(CC/PP): Structure and vocabularies 2.0. W3C

Working Draft 30 April 2007. http://www.w3.org/TR/

2007/WD-CCPP-struct-vocab2-20070430/

W3C Mobile Web Initiative. MWI device description

working group. http://www.w3.org/2005/MWI/DDWG

Zuquim, D., Guimares, G., Felgar de Toledo, M.B., 2006.

A Web service architecture providing QoS

management. In LA-WEB'06, the 4th Latin American

Web Congress, pp. 189-198.

WINSYS 2009 - International Conference on Wireless Information Networks and Systems

152