Application of Web Service Technologies on a B2B Communication Platform by Means of a Pattern and UML Based Software Development Process

Schnieders, Arnd

Titel: Application of Web Service Technologies on a B2B Communication Platform by Means of a Pattern and UML Based Software Development Process

Application of Web Service Technologies on a B2B Communication Platform by Means of a Pattern and UML Based Software Development Process

Zusammenfassung

Inhaltsangabe:Abstract:
There are about 230.000 establishments in the Spanish hotel, restaurant and catering industry accounting for a turnover of about 15.6 thousand million euros. All of them sell food to private consumers. On the other hand suppliers and traders supply the catering trade with food and beverage products. Usually the different players in this food distribution network trade products by means of orders which are placed manually. This is a process which can be enhanced through the application of computer and Internet technology. A project lately also supported by the Spanish government is supposed to fill this gap. This project is called Catanet and has been established three years ago. Actually the Catanet platform is used by more than 100 customers, amongst them very important industry players like Lauren Films, Pepsi, Unilever and Nestle. Some of them will carry out a significant part of their overall food orders by the Catanet platform, which corresponds to a turnover volume of many million euros.
In the former version of the Catanet platform clients had to apply a web page based interface in order to use the Catanet services. As this approach prohibited the full exploitation of the benefits the use of computer assistance provides (e.g. human participation still constitutes an inevitable and crucial part of the transaction, the interaction is completely asynchronous) an additional level is being added to the Catanet platform eliminating these shortcomings. During the time of this work the number of Catanet customers has grown explosively increasing also the diversity of the customers computer systems. Additionally new subprojects could be launched due to the acquisition of a government grant. These encompassed among others new value added services demanded by the customers like an instant messaging module and a module for the automatic update of the local product catalogue. The characteristics of the IT infrastructure of the new customers which will carry out transactions with a serious turnover via the Catanet platform and the necessity to integrate the new subprojects required an adaptation of the design of the platform prototype which had been developed by this time and which is described in this work.
Within this context the decision has been done to use .NET Framework based programs on the customer side instead of Java which had been used so far. The reasons for this were besides the easier integration with the IT […]

Leseprobe

Inhaltsverzeichnis

ID 7256

Schnieders, Arnd: Application of Web Service Technologies on a B2B-Communication

Platform by means of a Pattern- and URL-Based Software Development Process

Hamburg: Diplomica GmbH, 2003

Zugl.: Technische Universität Berlin, Technische Universität, Diplomarbeit, 2003

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Diplomica GmbH

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Printed in Germany

Diploma Thesis

CITeM La Salle Barcelona, last updated: 09/22/03

Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

Abstrakt

Die spanische Hotel-, Restaurant- und Cateringindustrie zählt ungefähr 230.000 Einrichtungen.

Diese sorgen für einen jährlichen Umsatz von etwa 15.6 Milliarden Euros. Alle diese Einrichtungen

verkaufen Nahrungsmittel an private Abnehmer. Gleichzeitig versorgen Produzenten und Händler

das Gaststättengewerbe mit Speisen und Getränken. Für gewöhnlich handeln die einzelnen

Teilnehmer des Nahrungsmitteldistributionsnetzwerks mit ihren Produkten auf der Grundlage

manuell aufgegebener Bestellungen. Dies ist ein Prozess, der durch den Einsatz von Computer-

und Internettechnologie effektiviert werden kann.

Ein jüngst auch von der spanischen Regierung unterstütztes und vor etwa drei Jahren

gegründetes Projekt mit dem Namen ,,Catanet" soll diese Lücke schließen.

In der aktuellen Version der Catanet-Plattform müssen die Kunden Webseiten-basierte

Schnittstellen verwenden, um auf die Catanet Dienste zuzugreifen. Über 100 verschiedene

Kunden nutzen bereits diese Catanet-Version, um Bestellungen aufzugeben, Produktkataloge zu

studieren, Versandbestätigungen zu verschicken usw. Diese Lösung jedoch weist erhebliche

Mängel auf. So stellt die menschliche Interaktion immer noch einen unabdingbaren Bestandteil

der über die Plattform abgewickelten Geschäftsprozesse dar. Zudem verläuft die Kunden-

Plattform-Interaktion weitgehend asynchron. Die Vorteile des Computereinsatzes werden somit

nicht voll ausgeschöpft.

Ziel dieser Diplomarbeit war es, eine zusätzliche Plattform zu planen und zu entwickeln, die die

direkte Integration der Kunden-ERPs in die Catanet-Plattform erlaubt. Die praktische Bedeutung

dieser Arbeit wird dadurch verdeutlicht, dass zahlreiche, sehr bedeutende Marktteilnehmer wie

Lauren Films, Pepsi, Unilever und Nestle bereits Verträge mit Catanet geschlossen haben und nun

darauf warten, in die neue Catanet-Version, die im Rahmen dieser Diplomarbeit entwickelt

werden sollte, integriert zu werden.

Da die neue Catanet-Plattform auf der Grundlage von Web Services Technologie entwickelt

werden sollte und Web Services momentan noch nicht ohne weiteres für den Einsatz in einem

kommerziellen Kontext geeignet sind, mussten zusätzliche Technologien untersucht werden, um

den Ansprüchen, die sich aus der kommerziellen Anwendung ergeben (so wie die Sicherheit und

Zuverlässigkeit der versendeten SOAP Nachrichten), Rechnung zu tragen. Darüber hinaus mussten

Erfordernisse, die die praktische Anwendung mit sich bringt, wie zum Beispiel mögliche Firewall-

Probleme, die Stabilität, Performanz und Implementierungs-/Integrationskosten, bei der Suche

nach geeigneten Technologien berücksichtigt werden.

Die spätere Entscheidung, .NET-Framework-basierte Programme kundenseitig zu verwenden bei

gleichzeitiger serverseitiger Verwendung von Java-Programmen, warf zudem die Schwierigkeit

auf, das .NET-Java Integrationsproblem bei gleichzeitiger Berücksichtigung der Kompatibilität mit

Diploma Thesis

CITeM La Salle Barcelona, last updated: 09/22/03

Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

den übrigen Technologien lösen zu müssen. Auch hier mussten die oben genannten Aspekte der

Praxistauglichkeit beachtet werden.

Die Tatsache, dass die Ergebnisse dieser Arbeit später von anspruchsvollen Kunden kommerziell

verwendet werden sollten, erforderte insbesondere auch die Betonung der Qualität der

entwickelten Software. Die Auswahl und Verfolgung eines geeigneten Softwareentwicklungs-

prozesses stellt ebenso ein Beispiel für die Anstrengung, dieses Ziel zu erreichen, dar wie die

Ausarbeitung und Verwendung einer passenden Teststrategie.

Die Resultate dieser Arbeit bestehen in einer ersten Java-basierten Implementierung der neuen

Plattform, bestehend aus über 12.000 Zeilen Quellcode, die in verschiedenen Modulen organisiert

sind, und einer umfassenden Studie, wie die neue Catanet Plattform entsprechend den oben

genannten Design-, Geschwindigkeits-, Qualitäts- und funktionalen Kriterien zu realisieren ist. Im

Rahmen dessen wurden zahlreiche Reliabilitäts- und Sicherheitstechnologien untersucht, bewertet

und im Plattformdesign berücksichtigt, obwohl sie aufgrund der Begrenzung der zur Verfügung

stehenden Zeit nicht mehr vollständig implementiert werden konnten.

Nahezu die Hälfte des entwickelten Quellcodes besteht aus Tests, die entsprechend der

ausgearbeiteten Teststrategie implementiert wurden. Außerdem wurde die Performanz des

entwickelten Systems analysiert, und Performanz -Flaschenhälse wurden identifiziert.

Diploma Thesis

CITeM La Salle Barcelona, last updated: 09/22/03

Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

Abstract

There are about 230.000 establishments in the Spanish hotel, restaurant and catering industry

accounting for an annual turnover of about 15.6 thousand million euros. All of them sell food to

private consumers. Additionally suppliers and traders supply the catering trade with food and

beverage products. Usually the different players in this food distribution network trade products

by means of orders which are placed manually. This is a process which can be enhanced through

the application of computer and Internet technology.

A project lately also supported by the Spanish government is supposed to fill this gap. This project

is called "Catanet" and has been established three years ago.

In the current version of the Catanet platform clients have to employ a web page based interface

in order to access the Catanet services. More than 100 different customers use this version of the

Catanet to place orders, look up product catalogs, confirm the shipping of orders, etc. But this

solution comes short on several aspects. Human participation for example still constitutes a crucial

part of the transactions and the interaction with the Catanet platform is completely

asynchronous. Therefore the benefits the use of computer assistance provides cannot be fully

exploited.

Thus the purpose of this thesis was to design and implement an additional level of the Catanet

platform which allows the integration of the customer's ERPs into the Catanet platform. The

practical relevance of this work becomes clear considering the fact that very important industry

players like Lauren Films, Pepsi, Unilever and Nestle have signed already contracts with the

Catanet waiting to be integrated by the new platform version which should be developed within

this work.

Since the new Catanet platform is supposed to be realized using Web Service technology and

Web Services are actually not yet ready for easily being utilized in a commercial context, a number

of additional technologies had to be investigated in order to meet the requirements (such as

security and exactly-once delivery of the SOAP messages) which make it eligible for Catanet

business transactions. Moreover certain real world constraints had to be taken into account like

for example the firewall compatibility of the analyzed technologies as well as their stability,

implementation/integration costs and perfomance. The later decision to use .NET Framework

based programs on the customer side while realizing the server side system in Java additionally

raised the difficulty to manage the .NET-Java integration while regarding the compatibility of the

integration technology with the security and reliability technologies. In addition the

abovementioned real world constraints also had to be taken into account for the selection of a

suitable .NET-Java integration mechanism.

Diploma Thesis

CITeM La Salle Barcelona, last updated: 09/22/03

Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

VII

The fact that the results of this work were supposed to be used in a commercial context by

demanding clients required also in particular the consideration of the quality of the developed

software. The selection and tracing of a suitable software development process as well as the

elaboration and application of an eligible test strategy are two examples for the effort to reach

this goal.

The result of this work is a first Java implementation of the new platform, comprising 12.000 lines

of sourcecode which are organized in several modules as well as a comprehensive study of how

to realize the new Catanet platform according to the abovementioned design, performance,

quality and functional criteria. Thereby numerous reliability and security technologies have been

investigated, evaluated and regarded by the platform design even though due to the time

constraints of this work they couldn't be fully implemented.

Almost half of the developed source code represents tests which are implemented according to

the elaborated test strategy. Moreover the performance of the developed system has been

analyzed and performance bottlenecks have been identified.

Diploma Thesis

CITeM La Salle Barcelona, last updated: 09/22/03

Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

VIII

Acknowledgements

I would like to seize this opportunity to express my thanks to anybody who made it possible for

me to write my diploma thesis in this great city making this part of my studies a very enriching

experience.

First of all many thanks to Dr. Xavier Ginesta for giving me the chance of working in one of his

projects and for being always very generous in granting me the freedom necessary to master the

challenge of meeting also the sometimes diverging demands on my work placed by the German

study regulations.

I want to express my special thanks also to Prof. Dr. Dr. hc. Radu Popescu-Zeletin and Stephan

Steglich who kindly agreed to accept the supervision of my diploma thesis in Germany.

Last but not least many thanks also to my good friend Frank Bergmann among others for only

making this project possible through his contacts and for never hesitating to offer his help in case

of problems.

Diploma Thesis

CITeM La Salle Barcelona, last updated: 09/22/03

Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

Table of Contents

Introduction

1.1

Motivation and Definition of the Project

1.1.1

Outline of the Catanet Project

1.1.2

Definition of the Main Tasks of this Work

1.2

Identification of Central Questions

1.2.1

Selection and Application of Appropriate Security

Mechanisms

1.2.2

Platform Design by Following an Appropriate Software

Development Process

1.2.3

Implementation Style

1.2.4

Transaction Reliability

1.2.5

System Integration

1.2.6

Real World Business Suitability: Speed and Stability

1.2.7

SOAP Communication Details

1.2.8

.NET-Java Integration

1.3

Overview of this Work

1.4

Objectives

Technological Background: Web Services

2.1

Introduction

2.2

Web Services Architecture: Just-In-Time Integration

2.3

Web Services Core Technologies

2.3.1

Packaging Layer: SOAP

2.3.1.1

SOAP Messages

2.3.1.2

The SOAP Data Types

2.3.1.3

RPC-style vs. Document-style SOAP

2.3.1.4

SOAP Implementations

2.3.2

Description Layer: WSDL

2.3.2.1

WSDL Files

2.3.3

Discovery Layer: UDDI

2.3.3.1

The UDDI Registry

Diploma Thesis

CITeM La Salle Barcelona, last updated: 09/22/03

Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

2.3.3.2

UDDI Registry Access

2.4

Conclusion

Concepts

3.1

Selection of an Appropriate Development Process

3.1.1

The Waterfall Model

3.1.2

Iterative / Incremental Software Development According to

Craig Larman

3.1.3

Extreme Programming

3.1.4

Summary / Conclusion

3.2

Catanet Proxy vs. Catanet API Approach

3.2.1

Criteria for Design Decision Proxy Delivery vs. API Solution 32

3.2.1.1

Costs

3.2.1.2

Performance

3.2.1.3

Stability

3.2.1.4

Adaptability / Extensibility

3.2.1.5

User Acceptance

3.2.1.6

Further Considerations

3.2.2

Conclusion

3.3

Technology Evaluation for Interface between Catanet Client

and Customer's IT Infrastructure

3.3.1

Socket Connection

3.3.2

RMI (Remote Method Invocation)

3.3.3

CORBA (Common Object Request Broker Architecture)

3.3.4

JNI (Java Native Interface)

3.3.5

Command Line Interface

3.3.6

Database

3.3.7

Directory Based Interaction

3.3.8

Web Service Interface

3.3.9

Conclusion

3.4

Technology Study: How to Provide a Reliable SOAP

Communication between the Catanet Client and Server 44

3.4.1

Reliability at the Transport Level

3.4.1.1

Reliable HTTP (HTTPR)

3.4.1.2

Blocks Extensible Exchange Protocol (BEEP)

3.4.2

Reliability at the SOAP Protocol Level

3.4.2.1

Web Services Reliability Specification (WS-Reliability)

3.4.2.2

Web Services Reliable Messaging Protocol (WS-

ReliableMessaging)

Diploma Thesis

CITeM La Salle Barcelona, last updated: 09/22/03

Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

3.4.3

SOAP in Connection with JMS

3.4.3.1

Main Characteristics and Advantages of JMS

3.4.3.2

JMS and Web Services

3.4.4

Electronic Business XML (ebXML)

3.4.4.1

ebXML Message Service Specification

3.4.4.2

Accessing ebXML via JAXM Clients

3.4.5

Implementing an Own Reliability Protocol

3.4.6

Summary / Conclusion

3.5

Technology Study: How to Provide a Secure SOAP

Communication between the Catanet Client and Server 65

3.5.1

Introduction

3.5.2

Secure Socket Layer (SSL)

3.5.2.1

SSL Features

3.5.2.2

Handshake

3.5.2.3

Protocol Processing

3.5.2.4

Advantages / Disadvantages

3.5.3

XML Security

3.5.3.1

XML Signature

3.5.3.2

XML Encryption

3.5.3.3

Advantages / Disadvantages

3.5.4

Summary / Conclusion

3.6

Technology Study: Integration of .NET Client with Axis SOAP

Server

3.6.1

Approach 1: Utilization of an Entirely to Java Ported .NET

Framework

3.6.2

Approach 2: Compiling Java Code to MSIL

3.6.3

Approach 3: Compiling Java Source Code to .NET Languages

and Vice Versa

3.6.4

Approach 4: Using a Bridge to Interlink a .NET with a Java

Runtime Environment

3.6.5

Approach 5: by Using a Web Service Interface between .NET

and Java

3.6.6

Summary / Conclusion

3.7

Test Strategy

3.7.1

Requirements

3.7.2

Test Process

3.7.3

Component Testing with JUnit

3.7.4

Integration Testing

3.7.4.1

Big Bang Integration

3.7.4.2

Bottom-up Integration

3.7.4.3

Top-down Integration

3.7.5

Coverage

Diploma Thesis

CITeM La Salle Barcelona, last updated: 09/22/03

Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

XII

3.7.5.1

Two Exemplary Coverage Models

3.7.5.2

Object Oriented Coverage

3.7.6

Summary / Conclusion

3.8

Summary / Conclusion

101

Realization

104

4.1

Software Development Process

105

4.1.1

Outline of Development Process

105

4.1.1.1

Phases

105

4.1.1.2

UML (Unified Modeling Language)

106

4.1.2

Plan and Elaborate Phase

106

4.1.2.1

Requirements Specification

107

4.1.3

Build Phase

121

4.1.3.1

Glossary

122

4.2

First Development Cycle

123

4.2.1

Analyze Phase

123

4.2.1.1

Conceptual Model

124

4.2.1.2

System Sequence Diagrams

130

4.2.1.3

Contracts

132

4.2.2

Design Phase

134

4.2.2.1

Expanded Real Use Cases

134

4.2.2.2

Collaboration Diagrams

140

4.2.2.3

Design of Class Diagrams

150

4.2.2.4

System Architecture Package Building

154

4.2.2.5

Complete Collaboration Diagrams Reflecting the Packet

Structure of the System

160

4.2.3

Construct Phase

168

4.2.4

Test Phase

169

4.3

Performance Measurements

170

4.3.1

First Series of Measurements: Analyzing the Overall Platform

Performance

170

4.3.1.1

Realization

171

4.3.1.2

Results

171

4.3.2

Second Series of Measurements: Evaluating the Performance

Only of the SOAP Based Message Transfer

172

4.3.2.1

Realization

173

4.3.2.2

Results

173

4.3.3

Third Series of Measurements: Evaluating the Performance of

the Server Side Processing

174

4.3.3.1

Realization

175

Diploma Thesis

CITeM La Salle Barcelona, last updated: 09/22/03

Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

XIII

4.3.3.2

Results

175

4.3.4

Further Series of Measurements: The Performance Bottleneck

Has Been Identified

176

4.3.4.1

Results

176

4.4

Second Development Cycle

178

4.4.1

Implementation of the Retransmission in Case of Error and

Directory Based System Integration

178

4.4.2

Expanded Real Use Case

178

4.5

Third Development Cycle

182

4.5.1

Implementation of the Order Status Update Requests

182

4.5.2

Acknowledge Order

182

4.5.2.1

Expanded Real Use Cases

182

4.5.2.2

Concepts / Conceptual Model

184

4.5.3

Shipping Confirmation

185

4.5.3.1

Expanded Real Use Case

185

4.5.3.2

Concepts / Conceptual Model

187

4.6

Summary / Conclusion

188

Conclusion

192

5.1

Summary

192

5.1.1

Chapter two

192

5.1.2

Chapter three

192

5.1.3

Chapter four

195

5.2

Future Prospects

197

5.3

Open Issues

200

List of References

201

Appendix

205

Diploma Thesis

CITeM La Salle Barcelona, last updated: 09/22/03

Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

XIV

Table of Illustrations

Figure 1: Overall Catanet Platform

Figure 2: Just-In-Time Integration

Figure 3: Web Services Technology Stack

Figure 4: SOAP Message Structure

Figure 5: Basic RPC Messaging Architecture

Figure 6: UDDI Registry Access

Figure 7: Catanet API Approach

Figure 8: Catanet Proxy Approach

Figure 9: SOAP Message Loss

Figure 10: SOAP Message Duplication

Figure 11: WS Protocol Stack: Reliable Transport Protocol

Figure 12: Reliable Messaging Through HTTPR

Figure 13: WS Protocol Stack: Reliable SOAP

Figure 14: JMS Reliable Message Transfer

Figure 15: JMS Based Service Bus

Figure 16: SOAP over JMS Architecture

Figure 17: Adapter Based JMS-Architecture

Figure 18: Reliable ebMS Message Transfer

Figure 19: Reliable Messaging Using JAXM and ebXML

Figure 20: SSL Protocol Stack

Figure 21: SSL Handshake

Figure 22: SSL Session Key Generation

Figure 23: XML Signature: Signing Data

Figure 24: XML Encryption: Encrypting Data

Figure 25: JNBridgePro Architecture

Figure 26: Antidecomposition Axiom

Figure 27: Anticomposition Axiom

Figure 28: Big Bang Integration 1

Figure 29: Big Bang Integration 2

Figure 30: Bottom-Up Integration 1

Figure 31: Bottom-Up Integration 2

Figure 32: Bottom-Up Integration 3

Figure 33: Top-Down Integration 1

Figure 34: Top-Down Integration 2

Figure 35: Top-Down Integration 3

Figure 36: Development P rocess Overview

106

Figure 37: Use Case Diagram

116

Figure 38: Development Process Build Phase

122

Figure 39: Development Process Development Cycle

123

Figure 40: Development Process Analyze Phase

124

Diploma Thesis

CITeM La Salle Barcelona, last updated: 09/22/03

Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

Figure 41: Conceptual Model of the First Development Cycle

130

Figure 42: Sequence Diagram 1 Place Order

131

Figure 43: Sequence Diagram 2 Approve Order

131

Figure 44: Sequence Diagram 3 Deliver Order (Accept Pending Service) 131

Figure 45: Development Process Design Phase

134

Figure 46: Collaboration Diagram Extract 1

144

Figure 47: Collaboration Diagram Extract 2

145

Figure 48: Collaboration Diagram Extract 3

146

Figure 49: Collaboration Diagram Extract 4

147

Figure 50: Collaboration Diagram Extract 5

148

Figure 51: Collaboration Diagram Extract 6

149

Figure 52: Class Diagram For the First Development Cycle

152

Figure 53: JBuilder Class Diagram 1

153

Figure 54: JBuilder Class Diagram 2

153

Figure 55: Package Structure of First Development Cycle

155

Figure 56: Service Package

156

Figure 57: Development Cycle 1 Collaboration Diagram 1

161

Figure 58: Development Cycle 1 Collaboration Diagram 2

162

Figure 59: Development Cycle 1 Collaboration Diagram 3

163

Figure 60: Development Cycle 1 Collaboration Diagram 4

164

Figure 61: Development Cycle 1 Collaboration Diagram 5

166

Figure 62: Development Cycle 1 Collaboration Diagram 6

167

Figure 63: Development Process Construct Phase

168

Figure 64: Development Process Test Phase

169

Figure 65: Performance Chart 1

172

Figure 66: Performance Chart 2

173

Figure 67: Performance Chart 3

175

Figure 68: Performance Chart 4

177

Diploma Thesis

CITeM La Salle Barcelona, last updated: 09/22/03

Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

Introduction

1.1

Motivation and Definition of the Project

1.1.1

Outline of the Catanet Project

There are about 230.000 establishments in the Spanish hotel, restaurant and

catering industry accounting for a turnover of about 15.6 thousand million

euros. All of them sell food to private consumers. On the other hand suppliers

and traders supply the catering trade with food and beverage products. Usually

the different players in this food distribution network trade products by means

of orders which are placed manually. This is a process which can be enhanced

through the application of computer and Internet technology.

A project lately also supported by the Spanish government is supposed to fill

this gap. This project is called "Catanet" and has been established three years

ago.

Actually the Catanet platform is used by more than 100 customers, amongst

them very important industry players like Lauren Films, Pepsi, Unilever and

Nestle. Some of them will carry out a significant part of their overall food

orders by the Catanet platform, which corresponds to a turnover volume of

many million euros.

In the former version of the Catanet platform clients had to apply a web page

based interface in order to use the Catanet services. As this approach

prohibited the full exploitation of the benefits the use of computer assistance

provides (e.g. human participation still constitutes an inevitable and crucial part

of the transaction, the interaction is completely asynchronous) an additional

level is being added to the Catanet platform eliminating these shortcomings.

During the time of this work the number of Catanet customers has grown

explosively increasing also the diversity of the customer's computer systems.

Additionally new subprojects could be launched due to the acquisition of a

government grant. These encompassed among others new value added

services demanded by the customers like an instant messaging module and a

module for the automatic update of the local product catalog.

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The characteristics of the IT infrastructure of the new customers which will

carry out transactions with a serious turnover via the Catanet platform and the

necessity to integrate the new subprojects required an adaptation of the design

of the platform prototype which had been developed by this time and which is

described in this work.

Within this context the decision has been done to use .NET Framework based

programs on the customer side instead of Java which had been used so far. The

reasons for this were besides the easier integration with the IT infrastructure of

the new customers the rising wish to provide a client module similar to a file

sharing program which should also provide an attractive user interface for the

manual interaction with the Catanet platform. Therefore the existing web

based user interface should be utilized by integrating an Internet Explorer into

the client module. For these applications .NET seemed to be more suitable that

Java.

Besides the provision of a business to business platform the Catanet project

aims to establish a product description code similar to the EAN13 barcode used

in supermarkets in order to settle up products at the counter. This electronic

barcode with the name "Registro Gastronómico" is dedicated to transport

product information via the Internet and consists of generic building blocks

(e.g. the product family hierarchy it belongs to, its vendors, its wrappers, etc.),

while the different product aspects (represented by the corresponding building

blocks) may only be modified by certain customers. The product descriptions

are held in a central oracle database provided by the Catanet platform and are

editable by the Catanet customers via a web interface according to their role.

1.1.2

Definition of the Main Tasks of this Work

The figure below depicts the latest version of the Catanet platform design from

a conceptual point of view.

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This figure shows the overall architecture of the Catanet

platform consisting of client and server side modules.

Figure 1: Overall Catanet

Platform

According to this model the Catanet platform consists of the modules at the

server side and the modules at the client side.

On the client side different integration modules assure that the client can be

integrated into the Catanet platform. Some clients for example dispose of an

ERP system like SAP that has to be integrated with the platform while other

clients prefer a user interface to connect to the Catanet platform.

The main communication channel between the client and the server side is to

be realized using the SOAP protocol. The purpose thereby is to realize a

synchronous communication between the customer's IT infrastructure with the

Catanet platform server.

The communication has to be secured, i.e. the integrity and confidentiality of

the transmitted data and the authenticity of the sender has to be assured.

Additionally it has to be proved for every transaction that the sender is

authorized to access the desired service.

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Internally the transaction data is transferred as a string in XML format.

Therefore a generic representation format that fits for any service request had

to be specified as well as specific formats for the different transactions.

Customers pass service requests as a string containing the request information.

This information may be encoded in a customer specific format. Thus the

requests received from the customers have to be parsed and the request data

has to be extracted before converting it into the XML representation.

On the server side the different transactions are delegated to the implementing

service modules after having extracted the transaction id from the service

requests. The service modules may be located at different servers.

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1.2

Identification of Central Questions

1.2.1

Selection and Application of Appropriate Security Mechanisms

Security technologies have to be found and applied in order to make the data

transfer confidential, resistant to modifications during the transport and to

ensure the authenticity of the transmitted data.

As there are many possible ways to reach this goal (e.g. through the application

of SSL, XML Security) the different security technologies had to be evaluated

concerning there suitability.

1.2.2

Platform Design by Following an Appropriate Software Development Process

The platform had to be designed carefully to ensure a good chance for

reusability of the components in further releases. Moreover as the Catanet

platform was still heavily under construction during the realization of this

project it became apparent that the flexibility of the software due its thorough

design was of great use whenever major changes of the overall architecture

were decided.

In order to make the platform maintainable and expandable by future team

members a high grade of comprehensibility of the software had to be given top

priority. This was especially important as the project is carried out in a university

context which is characterized by a high fluctuation of the developers. Thus a

great number of UML diagrams had to be produced for being able to maintain

and extend the system later.

1.2.3

Implementation Style

In addition to the detailed UML documentation of the platform extensive

source code comments had to be added to enhance the comprehensibility of

the software by later developers.

For the same reason the software has been implemented according to the

[SUNJ02] Java coding guidelines. Moreover the variable, method and object

names had to be chosen with the aim of making the source code maximal self

explanatory and long methods (more than 20 lines of code) had to be avoided.

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1.2.4

Transaction Reliability

Additionally to the security of the data transfer the transmission had to be

investigated concerning its reliability and finally appropriate mechanisms had to

be evaluated. This becomes clear imagining the case in which a customer

places an order at the Catanet platform using an unreliable connection. It could

happen now for example that the order is placed successfully at the Catanet

platform but the corresponding return message gets lost on its way to the

customer. The customer would now assume that the order hasn't been

processed properly and would start the retransmission of the same order

placement request. The Catanet server would process the request again with

the result that the order would be sent to the respective supplier twice thus

shipping the requested products once more.

1.2.5

System Integration

Different mechanisms (e.g. CORBA vs. RMI vs. socket connections vs. JNI etc.)

for the integration of the Catanet platform at the client side had to investigated

and evaluated.

1.2.6

Real World Business Suitability: Speed and Stability

Since important customers will carry out serious parts of their transactions via

the Catanet platform a reasonable speed of the software has been a must.

Therefore profound performance measurements had to be done in order to

find and eliminate performance bottlenecks.

As important as an appropriate speed of the software was a high grade of

accuracy which has been supposed to be reached through the exhaustive

employment of tests.

1.2.7

SOAP Communication Details

Concerning the realization of the SOAP based communication with the Catanet

platform several details have had to be analyzed like which SOAP message

transfer style to apply (RPC-style vs. message-style SOAP) and which SOAP

implementation to use.

1.2.8

.NET-Java Integration

The decision to use .NET Framework based programs on the customer side

raised a number of additional questions. This has been for example the

question how to integrate the .NET based client side with the Java based server

side.

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Likewise the integrateability of the potential security and reliability mechanisms

with the .NET Framework as well as with the Java based server side has had to

be taken into consideration while analyzing the security and reliability issues.

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1.3

Overview of this Work

Apart from the introduction this diploma thesis consists of three main chapters:

the "Technology Background" chapter briefly lining out the fundamentals of

the Web Services paradigm according to which the Catanet platform is being

implemented, the "Concepts" chapter which represents the theoretical main

part of this work and the "Realization" chapter which describes how the

implementations of this work have been done.

Each of these chapters consists of an introduction, which sketches the contents

of the chapter, the body and a final subchapter providing a summary and

drawing conclusions.

In the second chapter of this thesis an introduction to the fundamentals of the

Web Service philosophy is given as the Catanet platform is being implemented

according to the Web Services paradigm. The second chapter comprises also

the analysis of design and implementation questions related to the SOAP

protocol as raised in 1.2.7.

The "Concepts" chapter analyzes and answers the security, reliability and .NET-

Java integration issues stated in 1.2.1, 1.2.4, 1.2.8. It also addresses the overall

design decision whether to provide a client component or to provide only an

interface description for the integration of the Catanet customers which is

strongly related to the available system integration technologies as mentioned

in 1.2.5. Also this point has been analyzed and evaluated.

The issues of which Development Process to use and how to test the system

properly like brought up in 1.2.2. and 1.2.6 have been investigated and

answered likewise in this chapter.

Due to the extent of the "Concepts" chapter every subchapter also

encompasses here a leading introduction and trailing conclusion chapter just

like the main chapters of this thesis.

The "Realization" chapter describes how Craig Larman's development process

has been followed step by step in order to implement the first release of the

Catanet platform. It also deals with the performance measurements which have

been considered necessary according to 1.2.6.

The "Conclusion" chapter gives a summary of this work ("Summary"),

evaluates the future of Web Services for e-business ("Future Prospects") and

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names the tasks which couldn't be fulfilled because of the time constraints of

this work ("Open Issues").

Many UML diagrams have been evacuated to the Appendix due to their

dimension. The same holds for the detailed measuring results of the

performance measurements and details concerning the error handling. As more

than 12.000 lines of source code have been written in the context of this thesis

as part of the first Catanet platform release it would have gone beyond the

scope of this work to put print-outs of them into the Appendix as well.

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1.4

Objectives

An implemented platform which matches the abovementioned accuracy,

performance, reliability and security needs. These will be clearly defined in the

requirements analysis section of the main part of this work.

A second main objective of this work is the quality of the implementation, in

particular the comprehensibility and expandability of the program and the

reusability of its components.

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Technological Background: Web Services

As the Catanet platform will be built according to the Web Services philosophy,

this chapter shall give an introduction to the fundamental principles of Web

Services.

The communication between the Catanet clients and server will be realized by

means of SOAP and WSDL descriptions which constitute an important

component of the Web Service technology stack.

2.1

Introduction

Here is a definition of the Web Service term According to the W3C Working

Group on "Web Services Architecture Requirements" which can be found

under [CFN02]:

"A Web Service is a software application identified by a URI, whose interfaces

and binding are capable of being defined, described and discovered by XML

artifacts and that supports direct interactions with other software applications

using XML-based messages via Internet-based protocols."

The W3C definition says that all of the fundamental building blocks of Web

Services, which are the definition, discovery, access of Web Services are

strongly related to XML. Additionally also the bindings (to the underlying

"Internet-based protocols" for example) can be defined with XML.

Another important aspect is mentioned in this definition, which is the fact that

Web Services are not designed for direct human interaction. Rather, Web

Services operate at the code level; they are called by and exchange data with

other software. However Web Services will be incorporated into software

designed for human interaction as well.

Finally Web Services can be referenced by other software applications by means

of an URI.

There exist many other definitions of what Web Services are. Another

interesting one by "The Stencil Group" can be found under [Ste01]. For a short

introduction the definition cited above shall be sufficient.

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2.2

Web Services Architecture: Just-In-Time Integration

According to [STK02] the fundamental principle of Web Services is the Just-In-

Time integration.

The idea is that in the Web Services architecture, a service provider publishes a

description of the services he offers via a service registry. The service consumers

search the service registry to find a service that meets their needs. The service

consumer finally binds to the selected Web Service.

Binding refers to a service consumer actually using the service offered by a

service provider. The gag of Just-in-Time integration is that this can happen at

any time, especially at runtime. That is, a client might not know which

procedures it will be calling until it is running, searches the registry, and

identifies a suitable candidate. This is analogous to late binding in object-

oriented programming.

This figure illustrates the Just-In-Time integration concept which is

characteristic for the Web Service philosophy.

Figure 2: Just-In-Time

Integration

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The figure above illustrates how the Web Service Just-In-Time integration

works: a company P creates a number of Web Services and the WSDL file

which describes the corresponding Web Services. The company publishes the

WSDL based Web Service description to an UDDI registry.

Company R searches the UDDI registry for a Web Service that meets its

requirements and selects the Web Service offered by company P. An UDDI

registry can be searched according to different search criteria.

Company R now uses the WSDL description to create a client component

capable of making requests to the selected Web Service. Company R runs the

application. At runtime, the client component binds to the Web Service and

executes SOAP requests, passing data as XML over HTTP.

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2.3

Web Services Core Technologies

In this chapter I will give a short introduction to the technologies that form the

core of the Web Service architecture. In order to understand what is the focus

of these technologies and how they are related to the Web Service architecture

it makes sense to consider the constituting technologies as a Web Service

protocol stack.

Taking this point of view the Web Services architecture is implemented through

the layering of five types of technologies, organized into layers that build upon

one another.

Figure 3: Web Services

Technology Stack

This stack looks very similar to the TCP/IP network model used to describe the

architecture of Internet-based applications.

The additional packaging, description, and discovery layers in the Web Services

stack are the layers essential to providing the Just-In-Time Integration capability.

Because each part of the Web Services stack addresses a separate business

problem, only those pieces that make the most sense at any given time have to

be implemented. In our case for example the usage of discovery facilities

doesn't make sense as we incorporate the Web Service provider ourselves and

know already which Web Services will be used for which Catanet transaction.

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The Web Service description layer plays only a role in that WSDL descriptions

are used to generate the client side SOAP clients which connect to the Web

Services located at the Catanet server.

Therefore it will be given only a very concise introduction to UDDI and WSDL in

this chapter while SOAP will be discussed more in detail.

2.3.1

Packaging Layer: SOAP

SOAP`s place in the Web Services technology stack is a standardized packaging

protocol for messages shared by applications. The specification defines nothing

more than a simple XML-based envelope for the information being transferred,

and a set of rules for translating application and platform-specific data types

into XML representations.

SOAP is XML. That is, SOAP is an application of the XML specification. It relies

heavily on XML standards like XML Schema and XML Namespaces for its

definition and function.

The fundamental idea is that two applications, regardless of operating system,

programming language, or any other technical implementation detail, may

openly share information using nothing more than a simple message encoded

in a way that both applications understand. SOAP provides a standard way to

structure XML messages.

2.3.1.1

SOAP Messages

A SOAP message consists of an envelope containing an optional header and a

mandatory body.

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Figure 4: SOAP Message

Structure

Every Envelope may contain a Header element and must contain exactly one

Body element. The Body may contain as many child nodes as are required.

The core components of the SOAP Envelope specification are:

<s:Envelope>: the <s:Envelope> is the topmost container that comprises

the SOAP message.

<s:Header>: the optional <s:Header> contains additional blocks of

information about how the body payload is to be processed. Each element

contained by the Header is called a header block. The purpose of a header

block is to send contextual information relevant to the processing of a

SOAP message.

<s:Body>: the mandatory <s:Body> element contains the actual message

to be processed. Anything that can be expressed in XML syntax can go in

the body of the message. References may be used to reference external

information sources that are not part of the SOAP envelope (binary data for

example).

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2.3.1.2

The SOAP Data Types

The data types supported by the SOAP encoding style are the data types

defined by the "XML Schema data types" specification. All data types used

within a SOAP-encoded block of XML must either be taken directly from the

XML Schema specification or derived from types therein.

Data types supported by SOAP include also structs, arrays, character-array and

strings.

2.3.1.3

RPC-style vs. Document-style SOAP

SOAP has two related applications: RPC and EDI.

RPC-style SOAP

Remote Procedure Calls (RPC) are the basis of distributed computing, the way

for one program to make a procedure call on another, passing arguments and

receiving return values.

If SOAP is used for RPC (known as "RPC-style SOAP") then the XML payload of

the SOAP message will be a representation of parameter or return values.

Typically RPC-style SOAP messages come in pairs, as shown in the Figure

below: the request (the client sends function call information to the server) and

the response (the server sends return values back to the client).

Figure 5: Basic RPC

Messaging Architecture

The example below shows a fictive RPC-style SOAP message that represents a

request for getting the status of an order that has been placed before at the

Catanet server:

<s:Envelope XMLns:s="http://www.w3.org/2001/06/soap-envelope">

<s:Header>

<m:transaction XMLns:m="soap-transaction"

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s:mustUnderstand="true">

</m:transaction>

</s:Header>

<s:Body>

<n:getOrderStatus XMLns:n="urn:catanetOrderStatusService">

9874

</orderId>

</n:getOrderStatus>

</s:Body>

</s:Envelope>

The header remains the same for EDI and RPC style SOAP messages. What

changes is only the body tag which contains in this case the name of the Web

Service (catanetOrderStatusService), the name of the service method

(getOrderStatus) and the method parameter (orderId), which is in this case an

integer value.

[Sav02] discussed the advantages and disadvantages of RPC and EDI-style

SOAP.

Advantages of RPC-style SOAP are that it is easy to implement and that

successfully transferred SOAP messages can be recognized by the receipt of a

corresponding return value.

Disadvantages are that web services that are called by RPC style SOAP

messages become tightly coupled to the SOAP client. This means that

whenever there are any changes made to the signature of a web service

method this would break all of the clients using this web service. The fact that

Web Service method details like their signature are exposed to service

requestors with RPC-style SOAP is also denoted as tight coupling (of the Web

Service client to the Web Service server).

In addition to this RPC style SOAP messages are less resilient to network

problems like congestion. Using RPC style SOAP this would result in the

respective SOAP client to freeze until the expected return message finally

arrives or the transmission timer hits. The fact that the SOAP client blocks until

the RPC transaction has finished is also called synchronism of the Web Service

client and server.

Nevertheless RPC-based Web Services, which can be accessed by the JAX-RPC

APIs (Java API for XML Remote Procedure Calls), are much more popular due to

the simplicity of their use than EDI-based Web Services.

Document-style SOAP

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Electronic Document Interchange (EDI) is basis of automated business

transactions, defining a standard format and interpretation of financial and

commercial documents and messages.

If SOAP is used for EDI then the transferred XML payload will be an XML

document representing for example a purchase order.

The body of a document-style SOAP message is shown below:

<s:Body>

<n:purchaseOrder XMLns:n="urn:OrderService">

<person>Christopher Robin</person>

<dept>Accounting</dept>

</from>

<to>

<dept>Honey</dept>

</to>

<order>

<item>Pooh Stick</item>

</order>

</n:purchaseOrder>

</s:Body>

The advantages of Web Services accessed by EDI-style SOAP messages are first

of all that they are loosely coupled to the SOAP client. There are no method

signatures exposed to the SOAP client. This results in much more flexibility:

server changes don't lead to the necessity of client changes. EDI-style SOAP

clients exchange SOAP messages asynchronously with EDI-style SOAP servers.

This avoids the blocking of the SOAP clients while waiting for the SOAP request

and response being delivered. Hence message-style SOAP derives the full value

offered by the Web Services architecture making message -based SOAP more

robust and easier to change than RPC-style SOAP.

The problem with EDI-style SOAP now is that on one hand in order to work

properly it relies on asynchronous, guaranteed message delivery while on the

other hand this is a feature that is naturally not provided by the most popular

implementations of the Web Service stack. Normally JAXM is used in order to

make EDI-style SOAP calls with Java and JAXM doesn't allow to make

asynchronous SOAP calls with guaranteed delivery to arbitrary destinations. In

order to reach a reliable asynchronous SOAP message transfer with JAXM so

called profiles (like for example ebXML), which are domain-specific SOAP

applications, have to be used.

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2.3.1.4

SOAP Implementations

The integration of SOAP toolkits varies with the transport layer. Some

implement their own HTTP servers for managing the HTTP traffic by means of

which the SOAP messages are most frequently transferred. Some expect to be

installed as part of a particular web server, so that rather than serving up a web

page, the HTTP daemon hands the SOAP message to the toolkit's proxy

component, which does the work of invoking the code behind the Web

Service.

Whether the transport is built-in or pluggable, all SOAP toolkits provide the

proxy component, which parses and interprets the SOAP message to invoke

application code. The proxy must understand how to deal with things like

encoding styles and translation of native types of data into XML (and vice

versa).

When the proxy component is handed a SOAP message by a listener, it must

do three things:

Deserialize the message, if necessary, from XML into some native format

suitable for passing off to the code.

Invoke the code.

Serialize the response (if it's an RPC-style SOAP message) to the message

back into XML and hand it back to the transport listener for delivery back

to the requester.

2.3.2

Description Layer: WSDL

When a Web Service is implemented, it must make decisions on every level as

to which network, transport, and packaging protocols it will support. A

description of that service represents those decisions in such a way that the

Service Consumer can contact and use the service.

The Web Services Description Language (WSDL) is the de facto standard for

providing those descriptions. WSDL is not yet a W3C standard but a second

Working Draft of WSDL 1.2 was released by W3C in January 2003.

WSDL is an XML-based language used to describe a Web Service's external

interface.

Web Services can then be made available to other users by giving them a link

to its WSDL file. UDDI registries, described later, provide a place where

information about a Web Service can be published.

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2.3.2.1

WSDL Files

According to [SUN02] the elements of a WSDL file address what

is in the Web

Service, how

it is communicated and where the Web Service resides:

What: Definitions of messages and data types exchanged between client

and server

How: How the abstract interface (the portType) is bound to concrete

protocols. This can be for example SOAP is being used over HTTP.

Where: Specifies he location (URI) of the Web Service

2.3.3

Discovery Layer: UDDI

The discovery layer provides the mechanism for consumers to fetch the

descriptions of providers. One of the more widely recognized discovery

mechanisms available is the Universal Description, Discovery, and Integration

(UDDI) project.

2.3.3.1

The UDDI Registry

The UDDI project defines a searchable registry for services and their WSDL

descriptions so that consumers can automatically discover the services they

need.

The UDDI registry allows a business to publicly list a description of itself and the

services it provides. Potential consumers of those services can locate them

based on taxonomical information, such as what the service does or what

industry the service targets.

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UDDI requests are transferred via SOAP to an UDDI Registry for

receiving Web Service descriptions.

Figure 6: UDDI Registry

Access

2.3.3.2

UDDI Registry Access

According to [JeC02] two APIs are described by the UDDI specification: the

inquiry API and the Publishing API. They are accessed using the same

techniques but use different XML documents, data structures, and access

points. The inquiry API locates information about a business, the services a

business offers, the specifications of those services, and information about

what to do in a failure situation. Any read operation from a UDDI registry uses

one of the inquiry API's messages. The inquiry API does not require

authenticated access and is subsequently accessed using HTTP.

The Publishing API is used to create, store, or update information located in a

UDDI registry. All functions in this API require authenticated access to a UDDI

registry; the UDDI registry must have a logon identity, and the security

credentials for this identity must be passed as a parameter of the XML

document for each UDDI invocation. Because publishing requires authenticated

access, it is accessed over HTTPS, with a different URL than the one used with

the inquiry access point.

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2.4

Conclusion

In this chapter the basics of the Web Service architecture have been outlined

as the Catanet platform is implemented according to the Web Service

philosophy.

The functioning of Web Services can best be explained by referring to the

Web Service's

Just-In-Time integration principle. In order to make the

Just-In-Time integration possible three core technologies which are all XML

based can be utilized:

UDDI for locating Web Services and their description.

WSDL to describe Web Service interfaces in a way that they can be accessed

by a foreign program and SOAP to realize the communication between the

Web Service provider and consumer.

Not all of these technologies have to be utilized necessarily. In the case of the

Catanet platform for example only WSDL descriptions and the SOAP protocol

are used.

A more detailed look has been casted on the SOAP protocol as this is the

Web Service technology that is used most intensively for the Catanet

platform.

The fundamental idea of

SOAP is that two applications, regardless of

operating system, programming language and other technical

implementation details should be able to share information by means of

SOAP. Therefore SOAP defines a simple XML-based envelope and rules for

translating application and platform specific data types into XML

representation.

SOAP comes in two flavors: EDI-style SOAP and RPC-style SOAP. In RPC-style

SOAP the SOAP payload will be a representation of parameter and return

values. A RPC-style SOAP message is followed by a corresponding return

message holding the results of the service invocation. In EDI-style SOAP the

XML payload of a SOAP message is a whole XML document and the Web

Service request consists of a single message to the SOAP server without a

corresponding return message.

Main advantages of RPC-style SOAP are that RPC-style SOAP requests are

easy to implement in Java by means of the JAX-RPC libraries. Moreover the

successful delivery of a SOAP request can be immediately recognized by the

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Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

receipt of the corresponding return message. Disadvantages of RPC-style

SOAP are that it tightly couples Web Services clients to the Web Services

server, which means that Web Services internals like in this case a method

signature are exposed to the client. Therefore any changes to the Web

Service interface break the depending clients. Moreover the communication

between the RPC-style SOAP clients and server is synchronous, which means

that the SOAP clients block until they finally receive the SOAP response

message or the transmission timer hits. In case of network problems this

would cause a RPC-style SOAP client to freeze for a certain time.

In contrast to RPC-style SOAP EDI- or message-style SOAP works

asynchronously and loosely coupled. Therefore it derives the full value

offered by Web Services. The problem with EDI-style SOAP is that in order to

work properly it requires a data transmission with guaranteed message

delivery which is a feature that is not provided by the most popular

implementations of the Web Service protocol stack. Therefore it is very

unhandy and rarely used.

SOAP implementations may implement their own HTTP servers for

managing the HTTP traffic by means of which SOAP messages are normally

transferred. Others have to be installed as part of a particular web server. But

all of them have a SOAP proxy-component in common which parses and

interprets the incoming SOAP messages to invoke the application code.

Concerning the communication style RPC-style SOAP has been selected to be

used for the data transfer between the Catanet clients and server. The

abovementioned drawbacks of RPC-style SOAP are not that serious in our

case as a synchronized communication between the Catanet clients and

server is what has actually been the intention of this project. The other main

disadvantage of RPC-style SOAP, the lack of flexibility due to tightly coupling

between the SOAP server and client has been moderated through the

definition of a Web Service interface that is as flexible as possible, that is the

Web Service interface consists of methods for the different transactions

which expect a string containing the transaction data, like for example a

purchase order, as the only parameter. So this solution is something like a

mixture of EDI- and RPC-style SOAP trying to exploit the advantages of either

approach. Another advantage of RPC-style SOAP is that it eases the

implementation of an own reliability protocol as it can always be decided by

the presence of a return message that a SOAP transaction has succeeded and

no further retransmissions are necessary. Moreover a SOAP return value may

contain information concerning the success of the server side processing

which may fail for example because of semantical errors in the transaction

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Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

file.

Axis SOAP is used as the SOAP proxy implementation. Axis SOAP is open

source software and the de facto standard SOAP implementation for Java.

The Axis SOAP implementation is plugged in an Apache Tomcat server which

is used as HTTP handler. On the client side Axis SOAP client libraries and JAX-

RPC are used to generate SOAP messages and to send them to the SOAP

server.

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Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

Concepts

This chapter represents the theoretical main part of this work.

The first subchapter classifies Larman's Pattern and UML based incremental

software development process which has been utilized for the implementation

of the programs which have been developed in the context of this work. It is

compared to the Waterfall model and the lightweight Extreme Programming

development process.

The second subchapter discusses the overall design decision whether it is more

feasible to let the Catanet customers realize the integration of their IT

infrastructure into the Catanet platform on their own handing them only an

interface description or whether a Catanet module should be provided for this

purpose.

For being able to come to this decision the various technologies that could be

used to integrate the Catanet client module into the customer's IT

infrastructure have had to be investigated. This is what the second subchapter

deals with.

The following subchapters represent technology investigations analyzing

technologies to provide a reliable and secure SOAP communication and to

integrate the .NET based client side modules with the Java based server side

modules.

The last subchapter elaborates the test strategy that has been employed to test

the developed software.

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Application of Web Service Technologies on a B2B

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Software Development Process

3.1

Selection of an Appropriate Development Process

For the development of the system an iterative software development process

according to Larman has been utilized.

This incremental/iterative approach represents something like an intermediate

between the traditional Waterfall model and the lightweight Extreme

Programming. In order to be able to better classify Larman's iterative approach

these three development processes shall be outlined briefly in this chapter.

3.1.1

The Waterfall Model

The main characteristic of the Waterfall model is that each activity within the

development process (architectural design, detailed design, implementation,

component testing, system testing, and deployment of the system) is done

exactly once for the whole set of system requirements and it is not intended to

regress to a prior development step.

There are many points of the Waterfall model that have been criticized. Here

are some of them:

Problems with the software are not discovered until the system tests.

The requirements of the system are supposed to be definitely stated prior

to the system design, which is normally hard to realize as the design and

implementation frequently disclose requirements. A later change of the

requirements will make the development method unstable.

Also missing system components and unexpected development needs

discovered during the implementation are a problem as the return to a

former development step is not taken into account by the Waterfall model.

Another problem represents performance issues. The performance of the

system cannot be tested until it is almost implemented and performance

shortcomings due to an unsuitable design for example are then difficult to

fix.

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Application of Web Service Technologies on a B2B

Communication Platform by Means of a Pattern and UML Based

Software Development Process

3.1.2

Iterative / Incremental Software Development According to Craig Larman

In contrast to the waterfall model incremental development processes like the

one suggested by Craig Larman in [Lar98] carries out the different development

phases more than once.

Here is how Larman introduces his methodology:

"An iterative life-cycle is based on successive enlargement and refinement of a

system through multiple development cycles of analysis, design,

implementation and testing.

The system grows by adding new functions within each development cycle.

After a preliminary Plan and Elaborate phase, development proceeds in a Build

phase through a series of development cycles.

Each cycle tackles a relatively small set of requirements, proceeding through

analysis, design, construction and testing (see 1.1, p.17). The system grows

incrementally as each cycle is completed."

This has the advantage that the complexity of the development is always

controllable. Additionally implementations for the already completed

development cycles are early available. Therefore an early feedback is available

and shortcomings of the requirement analysis for example become apparent

earlier.

Larman's iterative development strategy is something like an intermediate

between the Waterfall model and Extreme Programming as on one hand he

stresses the importance of a detailed analysis and design like the Waterfall

model in order to reduce the risks involved in developing a software system

where changes in later phases of the development are more expansive than

early changes.

But on the other hand analysis and design are incremental and he avoids the

complexity of a large upfront design phase and allows the adoption of

changing requirements. Additionally Larman doesn't exclude the possibility to

defer requirement considerations to later phases of the development.

3.1.3

Extreme Programming

Extreme Programming takes Larman's approach to dispose with an extensive

upfront analysis and design to extremes in that the design of the code is

actually done while it's being written. Thereby the implementation always

focuses only on a small piece of software which is part of a bigger Use Case

(called story).

Details

Seiten
Erscheinungsform: Originalausgabe
Jahr: 2003
ISBN (eBook): 9783832472566
ISBN (Paperback): 9783838672564
DOI: 10.3239/9783832472566
Dateigröße: 10.9 MB
Sprache: Englisch
Institution / Hochschule: Technische Universität Berlin – Informatik
Erscheinungsdatum: 2003 (September)
Note: 1,0
Schlagworte: zuverlässigkeit performance java

Autor

Arnd Schnieders (Autor:in)

Application of Web Service Technologies on a B2B Communication Platform by Means of a Pattern and UML Based Software Development Process

Zusammenfassung

Leseprobe

Inhaltsverzeichnis

Details

Autor

Arnd Schnieders (Autor:in)