Tài liệu Systems Analysis and Design - Donald Yeates and Tony Wakefield - Second edition

Systems Analysis and Design
Donald Yeates and Tony Wakefield
Second edition

Contents

Preface xv
Acknowledgements xvii
1 The Context for Analysis and Design 1
1.1 Introduction 1
1.2 Business Analysis 2
1.2.1 Levels of Understanding 2
1.2.2 Linkage of IS to Business Objectives 3
1.3 Constraints 5
1.3.1 The User’s Organisation 5
1.3.2 Working Practices 5
1.3.3 Financial Control Procedures 6
1.3.4 Security and Privacy 6
1.3.5 Legal Considerations 7
1.3.6 Audit Requirements 7
1.3.7 Fallback and Recovery 7
1.4 Using IT for Competitive Advantage 8
1.5 Successful Systems 15
1.6 The Role of the Analyst and Designer 19
1.7 Ethical Considerations 21
1.8 Summary 24
Case Study: System Telecom 24
Case Study: LozCo Ltd 33
2 Approaches to Analysis and Design 34
2.1 Introduction 34
2.2 A Framework for Analysis and Design Methods 34
2.3 SSADM 38
2.4 Object-Orientation 39
2.5 Traditional Approaches 40
2.6 Structured Approaches 42
2.7 SSADM 48
2.8 Yourdon 51
2.9 Jackson 53
2.10 Merise 54
2.11 Rapid Application Development 56
2.11.1 Direct Systems Development Method (DSDM) 56
2.11.2 Principles of DSDM 56
2.12 Workflow Systems 58
2.13 Summary 60
Exercises 61
3 Communicating with People 63
3.1 Introduction 63
3.2 Types of Communication 64
3.3 Barriers to Communication 67
3.4 Improving Your Skills 70
3.4.1 Getting Information 70
3.4.2 Giving Information 72
3.4.3 Meetings 73
3.4.4 Presentations 75
3.5 Summary 82
Exercises 83
4 Building Better Systems 84
4.1 Introduction 84
4.2 Quality Concepts 85
4.3 Quality Gurus 86
4.4 The Cost of Poor Quality 89
4.5 Quality Management 93
4.6 ISO 9000 97
4.6.1 The TickIT Initiative 99
4.7 Quality in the Structured Life Cycle 99
4.7.1 Structured walkthroughs 100
4.7.2 Fagan Inspections 101
4.8 Summary 103
4.8.1 Inputs 105
4.8.2 Outputs 107
4.8.3 Evaluation 107
Exercises 107
5 Project Management 108
5.1 Introduction 108
5.2 Stages of System Development 108
5.2.1 Before Analysis and Design 108
5.2.2 Analysis and Design 110
5.2.3 After Analysis and design 112
5.3 Project Planning 113
5.3.1 Stages in Planning 114
5.3.2 Planning for Quality 119
5.4 Estimating 119
5.4.1 Estimating for Analysis and Design Work 120
5.4.2 Advantages of the Structured Approach 121
5.4.3 Using Function Point Analysis 122
5.5 Project Monitoring and Control 125
5.5.1 The Control of Quality 126
5.5.2 Documentation Control 127
5.5.3 Change Control 127
5.5.4 Configuration Management 128
5.6 PRINCE2 128
5.7 Summary 129
Exercises 129
6 Systems Analysis: Concepts 131
6.1 Introduction 131
6.2 What Is Systems Analysis? 131
6.3 Development Life Cycles 134
6.4 A Structured Approach 140
6.4.1 Structured Systems Analysis 141
6.5 The PARIS Model 142
6.6 Summary 143
7 Systems Analysis: Planning the Approach 144
7.1 Introduction 144
7.2 Objectives and Terms of Reference 146
7.3 Constraints 148
7.4 Preparing for Detailed Analysis 151
7.5 The Feasibility Study 153
7.6 Summary 155
Exercises 156
8 Systems Analysis: Asking Questions and Collecting Data 157
8.1 Introduction 157
8.2 Fact-finding Interviews 158
8.2.1 Planning the Interview 158
8.2.2 Conducting the Interview 164
8.3 Questionnaires 173
8.4 Observation 175
8.5 Record Searching 176
Contents vii
8.6 Document Analysis 176
8.7 Summary 177
Exercises 177
9 Systems Analysis: Recording the Information 180
9.1 Introduction 180
9.2 Data Dictionaries and CASE Tools 181
9.3 Data Flow Diagrams 182
9.3.1 DFD Components 182
9.3.2 DFD Hierarchies 183
9.4 Modelling Current Physical Processing 186
9.5 Entity Models 188
9.5.1 The Logical Data Structuring Technique 188
9.5.2 The Logical Data Model 192
9.6 Modelling Current Data 193
9.7 The Data Catalogue 195
9.8 Recording the Requirements 196
9.9 Summary 196
Exercises 197
Case Study: The Shark Loan Company 197
Case Study: Ravenelli Ice Cream 198
10 Object-Oriented Methods 200
10.1 Introduction 200
10.2 Principles of OO 201
10.2.1 Inheritance 201
10.2.2 Encapsulation 202
10.2.3 Polymorphism 203
10.3 Object-Oriented Models 203
10.3.1 Use Case Diagrams 204
10.3.2 Class Inheritance Diagrams 206
10.3.3 OO Behaviour Models 210
10.4 Summary 215
11 Systems Analysis: Modelling Systems Behaviour 217
11.1 Introduction 217
11.2 Creating a Logical Model of Current Processing 218
11.3 Modelling the Required System 219
11.4 Adding the Time Dimension 220
11.5 Modelling the Effects of System Events 222
11.6 Entity Life Histories 223
11.7 Producing Entity Life Histories 226
11.8 Effect Correspondence Diagrams 228
11.9 Producing Effect Correspondence Diagrams 229
11.10 Modelling Enquiries 230
11.11 Defining the User View of Processing 231
11.12 Modelling Input and Output Data 233
11.13 Modelling OO System Behaviour 234
11.14 Modelling Logic 234
11.15 Size and Frequency Statistics 237
11.16 Summary 239
Exercises 239
12 Systems Analysis: Meeting Business Requirements 242
12.1 Introduction 242
12.2 Agreeing the Options 243
12.2.1 Identifying Options 244
12.2.2 Choosing Between the Options 245
12.2.3 The Use of Prototyping 245
12.2.4 Quantification of Options 246
12.3 Identifying Benefits 249
12.4 Presenting the Requirement 251
12.5 Writing the Functional Specification 252
12.6 Business Analysis 253
12.7 Business Activity Modelling 258
12.8 Business Analysis and IT Strategy 259
12.8.1 IT SWOT 260
12.8.2 Requirements Engineering 262
12.9 Strategic Information Systems 263
12.10 PESTEL Analysis 265
12.11 Summary 267
Exercises 267
13 From Analysis to Design 269
13.1 Introduction 269
13.2 Bridging the Gap 270
13.3 Design Objectives and Constraints 273
13.3.1 Objectives 273
13.3.2 Constraints 274
13.4 Summary 275
14 Systems Design: Information Security 276
14.1 Introduction 276
14.2 Hacking and Viruses 278
14.3 The Purpose of Control 279
14.4 Input Controls 281
14.5 Output Controls 283
14.6 Processing Controls 284
14.7 Storage Controls 286
14.8 Audit Controls 287
14.9 Contingency Planning 287
14.10 Summary 290
Exercises 290
15 Systems Design: Human–Computer Interaction 291
15.1 Introduction 291
15.2 Agreeing the System Boundary 292
15.3 Output Design 292
15.3.1 Output Technology 296
15.3.2 Displaying Information on a Screen 297
15.3.3 The Use of Tables and Graphics 297
15.3.4 Specifying Outputs 299
15.4 Input Design 301
15.4.1 Keyboard Transcription from Clerical Documents 302
15.4.2 Direct Input onto the Computer System Via a
Peripheral Device 304
15.4.3 Direct Entry through Intelligent Terminals 305
15.4.4 Input by Speech 305
15.5 Dialogue design 306
15.5.1 Website Design 307
15.5.2 Dialogue Types 308
15.5.3 WIMP Interfaces 312
15.5.4 User Support 314
15.6 Ergonomics and Interface Design 315
15.7 Summary 317
16 Systems Design: System Interfaces 319
16.1 Introduction 319
16.2 Interfaces Defined 319
16.3 Analysing Interfaces 323
16.4 Physical Forms of Interfaces 326
16.5 Interfaces to Peripherals 331
16.6 Summary 332
17 Systems Design: Logical Data Design 334
17.1 Introduction 334
17.2 The Top-down View: Entity Modelling 335
17.2.1 The Entity Relationship Matrix 336
17.2.2 Summary of Entity Modelling 337
17.3 The Bottom-up View: Third Normal Form Analysis 338
17.4 Merging the Data Models 345
17.5 Testing the Data Model 346
x Contents
17.6 The Data Dictionary 347
17.6.1 Advanced Features of a Data Dictionary 348
17.7 Summary 349
Exercises 350
18 Systems Design: Files 352
18.1 Introduction 352
18.2 Types of Data 352
18.3 Storage Media 354
18.3.1 Magnetic Disk 355
18.4 File Organisation 356
18.4.1 Serial Organisation 357
18.4.2 Sequential Organisation 357
18.4.3 Indexed Sequential Organisation 358
18.4.4 Random Organisation 359
18.4.5 Full Index Organisation 360
18.4.6 Chained Data 360
18.5 Access Methods 362
18.6 Factors Influencing File Design 363
18.7 Summary 365
Exercises 365
19 Systems Design: Databases 366
19.1 Introduction 366
19.2 Database Concepts 367
19.3 Database Models 369
19.4 File Management Systems 370
19.5 Hierarchical Database Systems 372
19.6 Network Database Systems 373
19.7 Relational Database Systems 375
19.7.1 Data Structure 375
19.7.2 Data manipulation 376
19.8 RDBMS Design 380
19.9 Futures 382
19.10 Summary 383
20 Systems Design: Physical Data Design 384
20.1 Introduction 384
20.2 Quantifying the Data Storage Requirements 385
20.3 Assessing the Required System Performance 386
20.3.1 Factors Affecting System Performance 388
20.3.2 Overheads that Adversely Affect System Performance 389
20.4 Investigating the Chosen Hardware/Software Platform 390
20.4.1 Data Storage 391
20.4.2 Data Transfer 392
20.4.3 The Programming Language Used 393
Contents xi
20.5 Moving from Logical to Physical Data Design 393
20.5.1 Creating a Physical Data Design 394
20.5.2 Data Access Diagrams 395
20.5.3 Refining the Physical Data Design 396
20.6 Summary 397
Exercises 397
21 Systems Design: Data Communications 399
21.1 Introduction 399
21.2 Basic Concepts 399
21.3 The Use and Provision of Networks 403
21.4 Carrying Information across Networks 404
21.4.1 Local Area Networks 404
21.4.2 Wide Area Networks 405
21.5 Standards and Standards-making Bodies 406
21.5.1 The OSI Reference Model 406
21.5.2 The Upper Layers 407
21.5.3 The Lower Layers 408
21.5.4 The Transport Layer 409
21.5.5 The X and V Series Recommendations 410
21.5.6 TCP/IP 410
21.6 LANs, WANs and the Internet 411
21.6.1 Client/Server Architecture 412
21.6.2 LANs, WANs and the Internet 412
21.7 Markup languages 413
21.8 Summary 414
Exercises 415
22 Systems Implementation 417
22.1 Introduction 417
22.2 Coding and Unit Test 417
22.2.1 Employing Programmers to Write Code 418
22.2.2 Using Code Generators 419
22.3 Testing: Ensuring the Quality 420
22.4 Data Take-on and Conversion 423
22.5 User Training 425
22.6 Going Live 426
22.7 The Maintenance Cycle 431
22.8 Summary 432
23 Change Management 433
23.1 Introduction 433
23.2 Information Technology and People 434
23.2.1 The Role of Analysts and Designers 436
23.3 Change Management 437
23.3.1 Unfreezing, Moving and Refreezing 438
23.4 The People Project 440
23.4.1 Creating Involvement 440
23.4.2 Building Commitment 442
23.4.3 Providing Skills 443
23.4.4 Managing the Benefits 444
23.5 The Change Management Pay-off 445
23.6 Summary 446
24 What Next? 448
24.1 Introduction 448
24.2 How Did We Get Here? 448
24.3 What’s Happening to Work? 450
24.4 How Shall We Survive? 451
24.4.1 Globalisation 453
24.4.2 Technology and Organisation Design 455
24.5 Business Process Reengineering 457
24.6 Conversations and Conclusions 460
Bibliography and Web References 470
Appendices
1 An Analysis and Design Case Study Using Structured Methods 473
2 ISEB Qualifications 488
Index 491


Preface
This is a substantially new and different edition of Systems Analysis and Design.
We hope that the new materials bring it up to date and that we’ve
kept the best of the old. It has been written for people studying systems
analysis and design or who are already working in systems teams. People
who are involved in the development of new systems or the development of
new systems analysts, or both, have written it.
It is intended to be a practical book, easy to read and easy to use. It follows
the same structure as the previous edition and has new and updated
material in it. There are more case studies and exercises too and we’ve crossreferenced
the topics to the ISEB syllabus in systems analysis and design.
There is also a web site for the book for the first time. We’re excited about
the opportunities that this offers. We want to make it interesting and useful
to use. You’ll find more information about Denton Motor Holdings and
some answer pointers to some of the case study problems and exercises.
There are also some end-of-chapter quizzes and the answers to them. You
could use these to check your understanding as you go through the book.
For more information, log on to www.booksites.net/yeates.
We hope that you enjoy the book. It can’t tell you everything you need to
know about analysis and design; no book can do that. There is no substitute
for experience.
Finally our thanks to James Cadle, John Koenigsberger, Steve Copson and
Murdoch Mactaggart for reviewing some of the material for us, and to the
panellists who helped with the final chapter – Debbie Paul, Frank Jones,
Jean-Noel Ezingeard, Nigel Underwood and Richard Bevan. Also, we would
like to thank Amanda Thompson and Tim Parker at Pearson Education for
keeping our noses to the grindstone in the nicest possible way as well as
Lionel Browne and David Hemsley the project editors.
Donald Yeates
Tony Wakefield
February 2003
Disclaimer
The publishers and authors do not accept responsibility in any way for the
failure of analysis and design work carried out based on ideas in this book or
following your reading of the book. Whilst the ideas and good practices are
based on hard won experience, they need to be applied with skill and understanding
and take account of project circumstances. Good luck!