Analyzing Systems: Determining Requirements for Object-Oriented Development (Bcs Practitioner)

309 Pages·1994·2.11 MB·English

by  Roy Maclean

Analysing Systems:
determining requirements for object oriented development
(Web edition)
Roy MacLean, Susan Stepney, Simon Smith
Nick Tordoff, David Gradwell, Tim Hoverd, Simon Katz
First published in 1994 by
Prentice Hall International (UK) Ltd
Campus 400, Maylands Avenue
Hemel Hempstead
Hertfordshire, HP2 7EZ
A division of
Simon & Shuster International Group
(cid:1)c Logica Cambridge Ltd and Data Dictionary Systems Ltd
Permission is granted to make copies of the whole work for any purpose except
direct commercial gain. The copyright holders retain all other rights, including
but not limited to the right to make translations and derivative works, and the
right to make extracts and copies of parts of the work. Fair quotation is permitted
according to usual scholarly conventions.
ISBN 0-13-301433-9
This version typeset 26 July 2004
Contents
Preface xi
I Introduction to ORCA 1
1 Why ORCA? 3
1.1 The ORCA method 3
1.2 Analysis and design 3
1.3 An analysis method 5
1.4 Other OO methods 7
2 ORCA by example 9
2.1 Introduction 9
2.2 Preliminary analysis 9
2.3 Finding out what’s wrong 11
2.4 Prescribing a remedy 14
2.5 Specifying a solution 16
2.6 Change and development 25
2.7 Conclusion 25
3 ORCA’s key ideas 26
3.1 An analysis process needs to be tailorable 26
3.2 A system has purposes as well as behaviour 26
3.3 A system is a network of co-operating roles 27
3.4 A system may exhibit pathologies 28
3.5 Models can describe the Old World, or a New World 29
3.6 A system is embedded in an environment 30
3.7 IT systems are ways of implementing behaviour 31
3.8 Models can express different levels of abstraction 31
v
vi Contents
3.9 Overview of ORCA 33
II The Basic Process 35
4 Introduction to the case study 37
4.1 Introduction to Part II 37
4.2 Overview of the ORCA Basic Process 38
4.3 Brief description of the case study 40
5 Preliminary Analysis 45
5.1 Introduction 45
5.2 Initial understanding of the client’s world 45
5.3 Establish the terms of reference 46
5.4 Identify sources of information 50
5.5 Define the contractual task 50
6 Process Design 52
7 Old World Purpose 54
7.1 Introduction 54
7.2 NIMWeC as a manufacturing organisation 55
7.3 Investigating NIMWeC 59
7.4 Further investigation 66
8 Old World Behaviour 71
8.1 Introduction 71
8.2 The weaving of name tapes 72
8.3 Orders, batches and the batching process 82
8.4 From orders to name tapes 85
9 Pathology and Prescriptions 89
9.1 Introduction 89
9.2 Adding in the development objectives 90
9.3 Structuring pathologies, positing prescriptions 91
9.4 Evaluating the prescriptions 97
10 Specifying the New World 103
10.1 Introduction 103
10.2 What the New World looks like 104
10.3 Onward into development? 112
III Using the Modelling Languages 113
vii
11 Purpose and Behaviour 115
11.1 Why use models? 115
11.2 Purposive entities and Behavioural entities 116
12 Behavioural modelling 121
12.1 Histories and Frameworks 121
12.2 Object characterisation 124
12.3 Dynamic behaviour 129
12.4 Levels of abstraction 140
12.5 The Class and Framework constructs 146
12.6 Structural frameworks and temporal frameworks 147
12.7 Behaviours and Services 148
13 Do’s and don’ts 150
13.1 Introduction 150
13.2 Process 150
13.3 Modelling 151
13.4 Diagrams 151
13.5 Abstraction 152
13.6 Classification and specialisation 152
13.7 Naming 153
IV Tailoring the Process 155
14 Introduction to tailoring 157
14.1 Why do we need to tailor the process? 157
14.2 Overview of tailorings 157
15 Organising the organisation—National Parks 159
15.1 Analysis parameters 159
15.2 Preliminary analysis 160
15.3 Modelling the Old World 162
15.4 Determining the system pathology 164
15.5 Drawing conclusions—the Analysis Report 167
16 Shaking up the business—Just in Time 170
16.1 Analysis parameters 170
16.2 Preliminary analysis 171
16.3 Describing the Old World 172
16.4 Determining the Pathology 174
16.5 Specifying a New World 175
16.6 Prescribing Change 177
16.7 Behavioural requirements 178
viii Contents
16.8 Development and transition 181
17 A new Purpose in life—the Paperless Map 183
17.1 Analysis parameters 183
17.2 Preliminary analysis 184
17.3 New World behaviour 185
17.4 Development strategy 186
17.5 Enhancing our kitbag 187
18 No Old World—spreadsheets and telephony 190
18.1 Analysis parameters 190
18.2 Why omit the Old World? 190
18.3 Modelling or design? 192
18.4 No Old World processes 193
18.5 Summary 194
19 Nothing new under the sun—a lending library 196
19.1 The analysis strategy 196
19.2 A lending library 197
19.3 Other uses, other models 204
20 No-one to talk to—Ahab applied to NIMWeC 210
20.1 The need for tailoring 210
20.2 Balderdash 210
20.3 Ahab 211
20.4 Applying Ahab to NIMWeC 212
20.5 Outputs from Ahab 216
20.6 Adding Ahab to the analysis process 218
V Wider Issues 221
21 Putting together an analysis project 223
21.1 Planning, monitoring and estimation 223
21.2 Validation 224
21.3 HCI requirements 225
21.4 ‘Non-functional’ requirements 225
21.5 Configuration management 228
21.6 Tool support 228
22 Life after ORCA—onward into development 232
22.1 Design and implementation considerations 232
22.2 Design methods 234
22.3 The ORCA method 236
ix
VI Appendices 237
A Defining modelling languages 239
A.1 Introduction 239
A.2 Syntax 239
A.3 Semantics 242
B Grampus—the Purposive modelling language 244
B.1 Introduction 244
B.2 Roles and services 244
B.3 Cluster and co-operation 246
B.4 Formation, delegation and promotion 249
C Beluga—the Behavioural modelling language 252
C.1 Beluga models 252
C.2 Classes 252
C.3 Frameworks 257
C.4 Framework statics 258
C.5 Framework class relationships 261
C.6 Framework dynamics 262
C.7 Diagrammatic concrete syntax 270
C.8 Generalisation and abstraction 283
D Glossary 286
E Bibliography 292
F Index 294
x Contents
Preface
About this book
This book describes and explains ORCA (Object Oriented Requirements Capture
and Analysis). It is aimed at all those interested in the description and analysis of
complex systems such as businesses, social organisations, and so on. In particular,
it is aimed at those responsible for producing strategies for the use of Information
Technology (IT) and requirements for software development.
Although we refer to ORCA as a ‘method’, this book is not a manual to be
followed slavishly during the analysis process. The usefulness of such a manual
would in any case be questionable. Rather, this book presents and explains a set
of ideas about analysis, together with ways of using these ideas. We hope that
these ideas will be useful to the practising analyst. Consequently, the ideas are
presented primarily through worked examples, rather than in a generalised, ‘text
book’ manner. We believe that this illustrates better how the ideas can be used in
practice, and avoids the impression of a rigid, prescriptive method.
Producing and analysing models is a primary activity in ORCA and two com-
plementary modelling languages are provided for this purpose. These languages
are illustrated by example models throughout the book. In addition, formal syntax
definitions, together with explanations of each language construct, are provided in
appendices.
The other aspect of ORCA is its view of the analysis process. This is presented
as a basic process together with a number of process variants that are appropriate
in different analysis situations. ORCA includes a stage where the analyst should
decide onthekindofprocess requiredforthegivenanalysissituation. Thedifferent
processes illustrated in the book (using various case studies) can be used to help
in this choice of approach.
One of the example analyses (the weaving factory, in Part II) is considerably
more substantial than the others. This is intended to illustrate the analysis of
a system that is complex and unfamiliar—the very situation for which we want
xi
xii Preface
an analysis method. Using only ‘toy’ examples would not convey the difficulties
encountered (and, we hope, overcome) in real analyses.
Overview of the book
InPartIweintroduceORCA;thispartcanbereadasastand-aloneoverview ofthe
method. Chapter 1 sets the scene, and provides the motivation for developing an
analysis method, and for ORCA in particular. Chapter 2 illustrates ORCA using
a simple example based on a petrol filling station. The example is not intended
to be realistic either in scale or level of detail. However, most of the features of
ORCA are covered. Chapter 3 summarises the key ideas of ORCA, including some
that are not illustrated fully in Chapter 2.
In Part II we illustrate ORCA’s Basic Process in a weaving factory case study.
The various chapters introduce the main ORCA concepts in the context of the
example; they should be read in sequence. Chapter 4 introduces the weaving
factory case study, and gives an overview of the Basic Process. Chapter 5 con-
cerns Preliminary Analysis—gaining an initial understanding of the client’s world,
establishing the terms of reference of the analysis, and identifying sources of in-
formation. Chapter 6 concerns the activity of deciding on an appropriate analysis
process; in this case, the Basic Process is assumed to be adequate. Chapters 7 and
8 develop and analyse models of the Old World—the existing situation with the
weaving factory. Chapter 9 discusses pathologies (what is fundamentally wrong
with the current world) and prescriptions to remedy these. Chapter 10 specifies
a New World for the weaving factory—this includes both organisational changes
and IT developments.
In Part III we show, in some more detail, how the modelling languages can
be used. Chapter 11 discusses the difference between purposive and behavioural
models; Chapter 12 discusses behavioural modelling in depth; Chapter 13 offers
some general heuristics on using ORCA.
In Part IV we show how ORCA’s Basic Process may be tailored to suit different
analysis situations, using a variety of example case studies. Many of these are
inspired by real-world examples, but have been modified for explanatory purposes.
These examples can be used to provide a starting point for a specific tailoring.
Chapter 14 introduces theidea of tailoring the Basic Process. Chapter 15 considers
the analysis of a loose organisation of semi-independent units—in this case, a
federation of National Parks trusts. Chapter 16 looks at an example of radical
restructuring of a manufacturing business—a change from traditional stock control
to‘just-in-time’delivery. Chapter17examinesthecasewheretheoverallmissionof
an organisation changes and the existing world has to be re-engineered in the light
of the new purposes. Chapter 18 considers analysis situations where there does not
seemtobeanOldWorld,becausearadicallynewproductisbeingdeveloped, orthe
world is developing into new areas. Chapter 19 considers an analysis process that