ON THE INTEGRATION OF QOS MANAGEMENT IN WEB

SERVICE ARCHITECTURE

Abdallah Missaoui

and Kamel Barkaoui

ENIT,University of Tunis El Manar, Tunisia

CEDRIC-CNAM,Paris, France

Keywords: Quality of service, web service, performance, architecture.

Abstract: The web service consumer requires sometimes a service provider which gives functional and non-functional

requirement especially in e-business domain. In this paper, an overview on web services and their qualities

are described. We propose a new architecture which permits the management of QoS, by integrating a new

layer in the web service architecture.

1 INTRODUCTION

During the last decades, the access to web has

increased exponentially. Thus, the need to invoke a

service by a client application through network

became evident and important. This urged the

enhancement of the web services.

In addition, the value of web services increased

since they allow the connection to heterogeneous

applications. As a result, they became a very

powerful technology for building service oriented

architectures and have standardized access to legacy

services.

Such increasing value was reinforced by several

research activities which objective is to deploy an

architecture that integrates QoS management.

This domain is critical for the e-business

applications where the service consumer demands

some QoS requirements from the provider before

service performing.

This paper introduces an architecture model of

web service which insures the quality of the invoked

services. This model proposes a new method for

publication and discovery of the web service

integrating QoS criteria and also the functional

requirements.

2 DEFINITION OF WEB

SERVICE

In the literature, the most used definition of the web

service is as follows: «Web service is a software

application identified by a URI, whose interfaces

and bindings are capable of being defined,

described, and discovered as XML artifacts. A Web

service supports direct interactions with other

software agents using XML-based messages

exchanged via Internet-based protocols » (Jeffrey,

2002).

The web services are applications that connect

programs, object, databases or business processes

using the XML language and standard transport

protocols. They are complements of existing

programs and applications and have the function,

like a middleware, to make communication between

them. They assure not only the interoperability

between applications, but also the interoperability

between different operating systems and hardware.

The call of a distant object method is performed

through a transport web protocol (generally HTTP)

and XML for the exchanges format. While, the

classic middleware use specific network protocols to

each application, the data encapsulation in the XML

documents allows the web service (client and server)

to dialogue with environments and heterogeneous

information system.

430

Missaoui A. and Barkaoui K. (2007).

ON THE INTEGRATION OF QOS MANAGEMENT IN WEB SERVICE ARCHITECTURE.

In Proceedings of the Third International Conference on Web Information Systems and Technologies - Internet Technology, pages 430-433

DOI: 10.5220/0001286304300433

 SciTePress

3 ARCHITECTURE MODEL FOR

WEB SERVICE

The actual and well established model of service

web architecture (figure 1) is composed of three

principal entities (Guruge, 2004):

 The service provider: it answers to the demand

and return the request results. The provider

describes the service by a WSDL file which

represents the provider interface and must be

published in registers of type UDDI;

 The registers UDDI: they permit to reference

the service. The register is organized

according to six types of data;

 The service consumer: basing on the WSDL

file, the service consumer invokes the service

provider.

Figure 1: Web service architecture.

A service provider publishes a service

description to a registry. A service consumer then

finds the service description via the service registry

(UDDI), the services description contains sufficient

information for the service requestor to bind to the

service provider to use the service.

4 QUALITY OF SERVICE

CONSTRAINT

The user’s requirements enlarge with the need of

applications which increase constantly. It becomes

necessary to focus perfect information.

For the web services, it’s important to be able to

specify the request of the QoS before the invocation

of the web service mostly for the applications in the

domain of E-business. These requirements of QoS

can be classified under many themes according to

their context.

The quality of service covers many functions for

the working of web service such as the execution

time, availability, security and the transactions. In

the following section, we will define the different

aspects of QoS by arranging them by theme.

The first one concerns the quality of service

attached to the execution time. Many studies have

been interested to this type of quality of service

(Ran, 2003 – Mani, 2002 – serhani, 2005). These

qualities act directly on the operations progress and

determine the execution time. They include

availability, accessibility (it can be expressed like a

probability measure denoting the success rate or the

chance of a successful instance of service to a point

in time), the treatment capacity, the performance (it

is evaluated by a measure of the execution speed of

a request from the service which depend on the

execution time, the latency time and the bitrate) and

the robustness.

The second theme treats the quality attached to

the cost and the management of the configuration

(Serhani, 2005). The provider must assure the

transactions and guaranty the operations.

The last theme is related to the security. This

theme evaluates the reliability and the security of

mechanisms used like authentication, confidentiality

and data encoding (Beznosov, 2005). The security

aspect is a quality aspect for web services; since it is

invoked on public networks, like internet. The

provider can take many degrees of security

according to the service consumer and his

requirements (Mani, 2002).

5 BACKGROUND AND RELATED

WORK

Several research studies have treated the topic of the

QoS for the web services (Menasce, 2004 –

Diamadoupoulou, 2006). These studies focused, in

most cases, on the enhancement of the present

traditional architecture by the addition of different

supplementary entities and the extension of the

present standards as the SOAP protocol and the

UDDI.

The users expectations are very various with

regards to the adequacy of a web service to their

needs and to their requirements concerning QoS.

These requirements complicate the management

and slow down the process of services selection. The

users expect from the services to be adapted to their

needs and to guaranty the QoS of the operations.

registry

Service

Provider

Service

consumer

Publish service

Query Service

Return the

service contract

Bind

ON THE INTEGRATION OF QOS MANAGEMENT IN WEB SERVICE ARCHITECTURE

431

For the present architecture, we pointed out the

following two questions:

 Can the service satisfy the user requirements

concerning QoS and performance?

 Is the system reliable in the realization of the

critical operations essentially in the domain of the E-

business?

It is therefore necessary to build an architecture

model that supports the management of the QoS and

the discovery of the services according to the needs

of the users especially those non functional

requirements.

Our approach supports various QoS aspects

including performance, security and transaction. The

communication between different layers ensures an

efficient utilization of the underlying resources as

well as a better support of application-dependent

requirements.

In the next section, we describe the design of the

proposed architecture and we explain the new

processes of publication and of selection that

supports QoS.

6 A NEW SOLUTION FOR QOS

INTEGRATION IN WEB

SERVICE ARCHITECTURE

The model of web service architecture described

previously present several drawbacks.

In the domain of the e-business, the current

researches on the services are only based, in most

cases, on the functional requirements of service

invoked by the client.

Another drawback is that some UDDI registers

contain non functional links, and incorrect

information that lead, in most cases, non functional

operations.

The performance and the quality of service are

primordial for e-business applications. This non-

functional requirement depends on the logic of the

applications, networks, the transport protocols, and

also the used standards.

The control and the management of the attributes

of the service quality help to assure the good

progress of the operations, and to reach the levels of

QoS required by the consumers and consequently,

we maximize the profits.

Besides the traditional functionalities of services,

the description and the publication of QoS, allows

the consumer to choose the more suitable provider.

We propose a web service architecture that takes

into account the management of the service qualities

based on the present functional standards.

Figure 2: New model of web service architecture.

The addition of a new layer between the classic

registers UDDI on the one side and the supplier and

the consumer of service on the other side, permits

the management of the qualities and improves the

process of web services selection.

This new layer allows keeping the present

registers UDDI. This layer contains four systems to

communicate with the three entities which are the

provider, the client and the registers. A more

detailed description on the functionalities of these

systems will be provided in section 6.1.

We will choose between the two following

scenarios:

 The publication of the web services and

thereafter the discovery and the invocation

according to the classic methods using the

present standards but without assuring the

QoS;

 The publication of the service with the

proposed QoS and the discovery according to

the functional and non functional aspects of

the services.

For the present web services architecture, the

problem resides in the difficulty to modify this

architecture to support the QoS. We propose to add a

system that will communicate by itself with the

different entities (supplier, consumer and UDDI

registers) by assuring the QoS management while

keeping the functional present methods.

provider consumer

Registry

System of

certification

System of

selection

Requests filter

Interface filter

WEBIST 2007 - International Conference on Web Information Systems and Technologies

432

It allows publishing the web services with or

without the management of QoS in the same UDDI

6.1 Publication, Discovery and

Invocation

The proposed architecture present new entities:

 The system of selection: a list of services will

be received by this system from the UDDI

registers; the role of the selection system is to

classify the services according to their

qualities asked by the consumer.

 The system of certification: its role is to verify

the QoS declarations given by the supplier.

 The requests filter: it analyses the received

requests and extracts all tags of the document.

 The interface filter: it examines the received

files WSDL and extracts all QoS tags of the

document.

6.2 Description

By exploiting the studies of Chan (Chan, 2005), the

service supplier sends the WSDL file for his

publication to the UDDI register. This WSDL file

contains in addition to the basic tags, a new tag

describing the features and the specifications of the

QoS offered. Before treating this by the interface

filter, the system of certification verifies the

declarations of QoS given by the supplier.

Once the service is registered, it can be invoked

by all the clients.

On the other hand, the SOAP request sent by the

customer is a request proposed by KangChan Lee

and al (kangchan, 2003). It integrates requests

concerning quality in addition to functionalities.

This request will be analysed and sent to the UDDI

the services without any classification.

Next, the system of selection makes an

association between the requests concerning quality

of service and the available demands.

Such analysis will be made in the database using

XQuery requests (Boag, 2006). It classifies the

services found according to an order: The services

that answer the user's requirements better will be

classified as the first. The services that don't assure

the quality of service or that doesn't answer to the

required demands will be eliminated. Finally, the

system sends a SOAP answer to the consumer.

7 CONCLUSIONS

Web service is an application component accessible

over open protocols. Web service has supported

interoperable machine-to-machine interaction over

the Internet.

Researches are focused on how to improve the

present architecture in order to support the quality of

service.

In this paper, we have proposed an extension of

the web service architecture. We have added a new

layer between the classic registers and the two

entities (provider and client) of service.

This layer supervises the management of the

QoS and ameliorates the process of web services

selection and keeping functional of basic methods of

discovery and publication.

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