Virtual Web Services: Extension Architecture to Alleviate Open Problems in Web Services Technology

Virtual Web Services: Extension Architecture to Alleviate Open Problems in Web Services Technology

Julio Fernández Vilas (University of Vigo, Spain)
Copyright: © 2009 |Pages: 21
DOI: 10.4018/978-1-60566-042-4.ch004
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Abstract

Several open issues in Web services architecture are being solved by using different kinds of solutions. Standard high-availability techniques based on the use of Web servers, business-logic-based caching systems, dynamic binding of Web services by programming the access to a SOAP message content from the business logic layer, and other kinds of current open problems can now be handled using a common unique technique. What we propose is to apply virtualization techniques to Web services.
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Introduction

When referring to current Web service architecture, a very important aspect to take care of is the one related to the separation of roles and the meaning of each role inside the architecture. Although the distinction between client, provider, and directory is clear, a great part of the Web services technology is based on a Web service offered by a provider (Booth, Haas, McCabe, Newcomer, Champion, Ferris et al., 2004). That is, according to the roles of the current proposed architecture, the provider is intimately related to the Web service it actually offers. In fact, both Web service and provider are used as only one role inside the architecture, called service provider. Several open problems of the current architecture can be solved by redefining this way of conceiving the roles inside the architecture.

Within the current architecture, the relation between client and provider has been established based on the use of two concepts:

  • Binding. It is a process performed at development-time, consisting of adapting client software to the definition or description of a Web service.

  • Invocation. It takes place on runtime, and it can be defined as the process by which a running client application calls a Web service.

The revised version of the W3C architecture redefines and merges these two concepts as “interaction.” According to an “interaction” between client and provider, the binding is performed in a static way, so the way invocations must be performed is predefined. According to this:

  • Dynamic binding cannot be performed, or, at least, not in an automatic way. There are different options based on the use of metadata (“Web services invocation framework,” 2007) that enable the use of dynamic binding, but it is always mandatory to use metadata to access application data.

  • Once a client application is bound to a concrete Web service, the execution of the application will be bound to the service provider selected, initially, at development-time. It will be necessary to bind a new Web service if we decide to use a new service provider. And this means that it will be necessary to develop new code to adapt the client application to the new interface of the new Web service. Although it is possible to change the location of the server providing the Web service without needing to make any modification to client application code, this will be only useful for those providers that have developed and published a Web service in the same way, that is, with the same parameters (its names and types), the same namespaces, and so forth.

  • If a client application wants to use more than one provider in order to invoke the same equivalent service (offered by different service providers), the developer must bind the client application to each one of the Web services.

These and other less relevant problems have their origin in the fact that the role of “service provider” is not distinguished from the role of “Web service provider.” When we talk about service-oriented architectures (SOA) (Barry, 2003; Vinosky, 2002), we usually use the terms “clients” and “providers,” and we always relate these term with the use of services. We think it is necessary to slightly change the terminology, and use the terms “client application” when we refer to a SOA client, and “Web service provider” when we refer to a SOA provider.

In addition, we propose the creation of two new roles (as seen in Figure 1): the service provider (differentiated from the Web service provider), and the client entity (differentiated from the client application). The appearance of these two new roles will led us to a mandatory role separation. That is, Web services architecture is now composed of five roles: client entity, client application, directory, Web service provider, and service provider.

Figure 1.

New roles

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State Of The Art

In the following subsections we will analyze the state of the art in several open issues in the Web services technology.

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Table of Contents
Foreword
Torbjørn Skramstad
Preface
Khaled M. Khan
Acknowledgment
Khaled M. Khan
Chapter 1
Ghita Kouadri Mostefaoui
The ultimate effectiveness in terms of quality achievements should be a key concern of systems built from Web services. To this end, in this chapter... Sample PDF
The Development, Testing, and Deployment of a Web Services Infrastructure for Distributed Healthcare Delivery, Research, and Training
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Chapter 2
Abdelghani Benharref, Mohamed Adel Serhani, Mohamed Salem, Rachida Dssouli
Web services are a new breed of applications that endorse large support from main vendors from industry as well as academia. As the Web services... Sample PDF
Multi-Tier Framework for Management of Web Services' Quality
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Chapter 3
Krishna Ratakonda
In this chapter we present an overview of research and development efforts across several different technical communities aimed at enabling... Sample PDF
Quality Models for Multimedia Delivery in a Services Oriented Architecture
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Chapter 4
Julio Fernández Vilas
Several open issues in Web services architecture are being solved by using different kinds of solutions. Standard high-availability techniques based... Sample PDF
Virtual Web Services: Extension Architecture to Alleviate Open Problems in Web Services Technology
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Chapter 5
Witold Abramowicz
The following chapter focuses on the problem of the proper definition of non-functional properties and methods that may be applied in order to... Sample PDF
Profiling of Web Services to Measure and Verify their Non-Functional Properties
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Chapter 6
Kyriakos Kritikos
As the Web service (WS) paradigm gains popularity for its promise to transform the way business is conducted, the number of deployed WSs grows with... Sample PDF
Enhancing the Web Service Description and Discovery Processes with QoS
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Chapter 7
Michael C. Jaeger, Matthias Werner
This chapter presents the definition of relevant terminology and a conceptual model of the basic terms. The chapter starts with the presentation of... Sample PDF
Web Services Dependability
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Chapter 8
Frederic Montagut, Refik Molva, Silvan Tecumseh Golega
Composite applications leveraging the functionalities offered by Web services are today the underpinnings of enterprise computing. However, current... Sample PDF
Transactional Composite Applications
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Chapter 9
Enrico Pontelli, Tran Cao Son, Chitta Baral
This chapter presents a comprehensive logic programming framework designed to support intelligent composition of Web services. The underlying model... Sample PDF
A Logic Programming Based Framework for Intelligent Web Service Composition
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Chapter 10
Daniel Brenner, Barbara Paech, Matthias Merdes, Rainer Malaka
For the foreseeable future, testing will remain the mainstay of software quality assurance and measurement in all areas of software development... Sample PDF
Enhancing the Testability of Web Services
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Chapter 11
Ghita Kouadri Mostefaoui, Zakaria Maamar, Nanjangud C. Narendra
This chapter presents our research initiative known as aspect-oriented framework for Web services (AoF4WS). This initiative looks into the role of... Sample PDF
Aspect-Oriented Framework for Web Services (AoF4WS): Introduction and Two Example Case Studies
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Chapter 12
Ty Mey Eap, Marek Hatala, Dragan Gaševic, Nima Kaviani, Ratko Spasojevic
The lack of intrinsic and user control in the identity management of today Internet security hampers the research in the area of Semantic Web and... Sample PDF
Open Security Framework for Unleashing Semantic Web Services
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Chapter 13
Vishal Dwivedi
This chapter underlines the importance of security service level agreements (SLAs) for Web services. As Web services are increasingly incorporated... Sample PDF
Providing Web Services Security SLA Guarantees: Issues and Approaches
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Chapter 14
Fatih Oguz
This chapter describes a research study with an objective to explore and describe decision factors related to technology adoption. The study... Sample PDF
Adoption of Web Services in Digital Libraries: An Exploratory Study
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Chapter 15
Bijoy Majumdar
Change is the only constant, and this concept holds good for services too. Service maintenance is the most tedious and longest phase of service... Sample PDF
Service Evolution and Maintainability
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Chapter 16
Pauline Ratnasingam
This chapter aims to examine the extent of Web services usage and quality, applying the balanced scorecard methodology in a small business firm as... Sample PDF
The Role of Web Services: A Balance Scorecard Perspective
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