I Object Models 1
1 Introduction 3
1.1 Why Model? . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2 Guiding Example: Study-Right University . . . . . . . . . . . . 10
1.3 From Concrete to Abstract to Objects . . . . . . . . . . . . . . 12
1.4 The High Art of Giving Examples . . . . . . . . . . . . . . . . 14
1.5 Scenarios and Stories . . . . . . . . . . . . . . . . . . . . . . . 19
1.6 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
1.6.1 Abstract vs. Concrete . . . . . . . . . . . . . . . . . . . 21
1.6.1.1 Terms and Definitions . . . . . . . . . . . . . 21
1.6.1.2 Chess . . . . . . . . . . . . . . . . . . . . . . 21
1.6.2 Giving Examples . . . . . . . . . . . . . . . . . . . . . 22
1.6.2.1 Mau Mau . . . . . . . . . . . . . . . . . . . 22
1.6.2.2 Battleships . . . . . . . . . . . . . . . . . . . 23
1.6.2.3 Mancala . . . . . . . . . . . . . . . . . . . . 24
1.6.2.4 Mensch Ärgere Dich Nicht . . . . . . . . . . 26
1.6.2.5 Towers of Hanoi . . . . . . . . . . . . . . . . 27
1.6.2.6 ATM Money Withdrawal . . . . . . . . . . . 27
1.6.2.7 Borrowing Electronic Books from a Library . 28
1.6.2.8 Trouble Ticket System . . . . . . . . . . . . . 28
1.6.2.9 Webshop . . . . . . . . . . . . . . . . . . . . 28
1.6.3 User Stories / Scenarios . . . . . . . . . . . . . . . . . 29
1.6.3.1 Mau Mau . . . . . . . . . . . . . . . . . . . 29
1.6.3.2 Battleships . . . . . . . . . . . . . . . . . . . 29
1.6.3.3 Mancala . . . . . . . . . . . . . . . . . . . . 29
1.6.3.4 Mensch Ärgere Dich Nicht . . . . . . . . . . 30
1.6.3.5 Towers of Hanoi . . . . . . . . . . . . . . . . 30
1.6.3.6 ATM Money Withdrawal . . . . . . . . . . . 30
1.6.3.7 Borrowing Electronic Books from Library . . 30
1.6.3.8 Trouble Ticket System . . . . . . . . . . . . . 30
1.6.3.9 Webshop . . . . . . . . . . . . . . . . . . . . 30
2 Object Diagrams 31
2.1 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.1.1 Mau Mau . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.1.2 Battleship . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.1.3 Mancala . . . . . . . . . . . . . . . . . . . . . . . . . . 40
2.1.4 Mensch Ärgere Dich Nicht . . . . . . . . . . . . . . . . 40
2.1.5 Towers of Hanoi . . . . . . . . . . . . . . . . . . . . . 40
2.1.6 ATM Money Withdrawal . . . . . . . . . . . . . . . . . 40
2.1.7 Borrowing Electronic Books from Library . . . . . . . . 40
2.1.8 Trouble Ticket System . . . . . . . . . . . . . . . . . . 40
2.1.9 Webshop . . . . . . . . . . . . . . . . . . . . . . . . . 41
3 From Objects to Classes 43
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.2 Deriving Class Diagrams from Object Diagrams . . . . . . . . . 44
3.3 About Cardinalities . . . . . . . . . . . . . . . . . . . . . . . . 50
3.4 Correct Use of Inheritance . . . . . . . . . . . . . . . . . . . . 53
3.5 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.5.1 Mau Mau . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.5.2 Battleships . . . . . . . . . . . . . . . . . . . . . . . . 54
3.5.3 Mancala . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.5.4 Mensch Ärgere Dich Nicht . . . . . . . . . . . . . . . . 54
3.5.5 Towers of Hanoi . . . . . . . . . . . . . . . . . . . . . 55
3.5.6 ATM Money Withdrawal . . . . . . . . . . . . . . . . . 55
3.5.7 Borrowing Electronic Books from Library . . . . . . . . 55
3.5.8 Trouble Ticket System . . . . . . . . . . . . . . . . . . 55
3.5.9 Webshop . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.5.10 Matching . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.5.11 Deriving Object- and Class Diagrams . . . . . . . . . . 57
3.5.12 Connect Four Game . . . . . . . . . . . . . . . . . . . 57
4 Translating Diagrams to Java Code. . . . 59
4.1 Class Diagrams to Java Code . . . . . . . . . . . . . . . . . . . 60
4.1.1 Bidirectional Associations: Managing Referential Integrity 64
4.1.2 Choosing the Right Container Class for To-Many Associations  . . . 67
4.1.3 Generated Code . . . . . . . . . . . . . . . . . . . . . . 68
4.2 Object Diagrams to Java Code . . . . . . . . . . . . . . . . . . 71
4.3 Generic Implementations of Object Diagrams . . . . . . . . . . 75
4.4 eDobs as Runtime Model Explorer . . . . . . . . . . . . . . . . 78
4.5 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
4.5.1 Study-Right University . . . . . . . . . . . . . . . . . . 80
4.5.2 Mau Mau . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.5.3 Battleships . . . . . . . . . . . . . . . . . . . . . . . . 82
4.5.4 Mancala . . . . . . . . . . . . . . . . . . . . . . . . . . 84
4.5.5 Mensch Ärgere Dich Nicht . . . . . . . . . . . . . . . . 84
4.5.6 Towers of Hanoi . . . . . . . . . . . . . . . . . . . . . 85
4.5.7 ATM Money Withdrawal . . . . . . . . . . . . . . . . . 85
4.5.8 Borrowing Electronic Books from Library . . . . . . . . 86
4.5.9 Trouble Ticket System . . . . . . . . . . . . . . . . . . 86
4.5.10 Webshop . . . . . . . . . . . . . . . . . . . . . . . . . 87
4.5.11 Connect Four Game . . . . . . . . . . . . . . . . . . . 87
4.5.12 Derive Classes from Code . . . . . . . . . . . . . . . . 88
4.5.13 Referential Integrity Templates . . . . . . . . . . . . . . 88
II Behavior 91
5 Storyboards 93
5.1 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
5.1.1 Mau Mau . . . . . . . . . . . . . . . . . . . . . . . . . 102
5.1.2 Battleships . . . . . . . . . . . . . . . . . . . . . . . . 103
5.1.3 Mancala . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.1.4 Mensch Ärgere Dich Nicht . . . . . . . . . . . . . . . 104
5.1.5 Towers of Hanoi . . . . . . . . . . . . . . . . . . . . . 104
5.1.6 ATM Money Withdrawal . . . . . . . . . . . . . . . . 104
5.1.7 Borrowing Electronic Books from Library . . . . . . . 105
5.1.8 Trouble Ticket System . . . . . . . . . . . . . . . . . . 105
5.1.9 Webshop . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.1.10 Connect Four Game . . . . . . . . . . . . . . . . . . . 106
6 Algorithm Design 109
6.1 Model Exploration . . . . . . . . . . . . . . . . . . . . . . . . 110
6.2 Object Games . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
6.3 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
6.3.1 Mau Mau . . . . . . . . . . . . . . . . . . . . . . . . . 124
6.3.2 Battleships . . . . . . . . . . . . . . . . . . . . . . . . 124
6.3.3 Mancala . . . . . . . . . . . . . . . . . . . . . . . . . 124
6.3.4 Mensch Ärgere Dich Nicht . . . . . . . . . . . . . . . 124
6.3.5 Towers of Hanoi . . . . . . . . . . . . . . . . . . . . . 125
6.3.6 ATM Money Withdrawal . . . . . . . . . . . . . . . . 125
6.3.7 Borrowing Electronic Books from Library . . . . . . . 125
6.3.8 Trouble Ticket System . . . . . . . . . . . . . . . . . . 126
6.3.9 Webshop . . . . . . . . . . . . . . . . . . . . . . . . . 126
6.3.10 Connect Four Game . . . . . . . . . . . . . . . . . . . 126
7 Simple Java with Object Models 127
7.1 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
7.1.1 Mau Mau . . . . . . . . . . . . . . . . . . . . . . . . . 140
7.1.2 Battleships . . . . . . . . . . . . . . . . . . . . . . . . 140
7.1.3 Mancala . . . . . . . . . . . . . . . . . . . . . . . . . 140
7.1.4 Mensch Ärgere Dich Nicht . . . . . . . . . . . . . . . 141
7.1.5 Towers of Hanoi . . . . . . . . . . . . . . . . . . . . . 141
7.1.6 ATM Money Withdrawal . . . . . . . . . . . . . . . . 141
7.1.7 Borrowing Electronic Books from Library . . . . . . . 141
7.1.8 Trouble Ticket System . . . . . . . . . . . . . . . . . . 142
7.1.9 Webshop . . . . . . . . . . . . . . . . . . . . . . . . . 142
7.1.10 Connect Four Game . . . . . . . . . . . . . . . . . . . 142
8 Testing 143
8.1 Testing in Java with JUnit . . . . . . . . . . . . . . . . . . . . . 145
8.2 Creating our First Test . . . . . . . . . . . . . . . . . . . . . . 146
8.3 JUnit Assertions . . . . . . . . . . . . . . . . . . . . . . . . . . 149
8.4 Testing for Errors . . . . . . . . . . . . . . . . . . . . . . . . . 151
8.5 Test Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
8.6 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
8.6.1 Mau Mau . . . . . . . . . . . . . . . . . . . . . . . . . 154
8.6.2 Battleships . . . . . . . . . . . . . . . . . . . . . . . . 154
8.6.3 Mancala . . . . . . . . . . . . . . . . . . . . . . . . . . 155
8.6.4 Mensch Ärgere Dich Nicht . . . . . . . . . . . . . . . . 155
8.6.5 Towers of Hanoi . . . . . . . . . . . . . . . . . . . . . 156
8.6.6 ATM Money Withdrawal . . . . . . . . . . . . . . . . . 156
8.6.7 Borrowing Electronic Books from Library . . . . . . . 156
8.6.8 Trouble Ticket System . . . . . . . . . . . . . . . . . . 157
8.6.9 Webshop . . . . . . . . . . . . . . . . . . . . . . . . . 157
8.6.10 Connect Four Game . . . . . . . . . . . . . . . . . . . 158
9 Story Diagram Idioms 159
9.1 Story Diagram Control Flow Idioms . . . . . . . . . . . . . . . 159
9.1.1 Empty Story Diagram . . . . . . . . . . . . . . . . . . 159
9.1.2 Java Statements in Story Diagrams . . . . . . . . . . . . 160
9.1.3 Sequences of activities . . . . . . . . . . . . . . . . . . 161
9.1.4 If-Then-Else Control Flow . . . . . . . . . . . . . . . . 161
9.1.5 Loop Control Flow . . . . . . . . . . . . . . . . . . . . 164
9.1.6 Return Values . . . . . . . . . . . . . . . . . . . . . . . 167
9.1.7 Recursion . . . . . . . . . . . . . . . . . . . . . . . . 168
9.1.8 Exception Handling . . . . . . . . . . . . . . . . . . . 168
9.2 Story Pattern Elements . . . . . . . . . . . . . . . . . . . . . . 170
9.2.1 Pattern Variables and Pattern Objects . . . . . . . . . . 170
9.2.2 Matching Objects and Links . . . . . . . . . . . . . . . 172
9.2.3 Attribute Conditions . . . . . . . . . . . . . . . . . . . 173
9.2.4 Java Statements in Story Patterns, a Complex Example for the FAMous Fujaba Abstract Machine . . . . . . . . 174
9.2.5 Attribute Assignments, Object and Link Creation and Deletion  . . . . . . . . . . . . . . . . . 179
9.2.6 Using Marker Nodes as Collections . . . . . . . . . . . 183
9.2.7 Handling Multiple Matches: For-Each Activities . . . . 186
9.2.8 Some Special Pattern Elements: Type Casts . . . . . . . 189
9.2.9 Some Special Pattern Elements: Paths . . . . . . . . . . 192
9.2.10 Handling Multiple Matches: Set Valued Pattern Objects 195
9.2.11 Important Pattern Elements We Did Not Yet Use: Optional Objects, Negative Objects, Complex Constructors 196
9.3 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
9.3.1 Mau Mau . . . . . . . . . . . . . . . . . . . . . . . . . 199
9.3.2 Battleships . . . . . . . . . . . . . . . . . . . . . . . . 199
9.3.3 Mancala . . . . . . . . . . . . . . . . . . . . . . . . . . 200
9.3.4 Mensch Ärgere Dich Nicht . . . . . . . . . . . . . . . . 200
9.3.5 Towers of Hanoi . . . . . . . . . . . . . . . . . . . . . 200
9.3.6 ATM Money Withdrawal . . . . . . . . . . . . . . . . . 200
9.3.7 Borrowing Electronic Books from Library . . . . . . . 201
9.3.8 Trouble Ticket System . . . . . . . . . . . . . . . . . . 201
9.3.9 Webshop . . . . . . . . . . . . . . . . . . . . . . . . . 201
9.3.10 Connect Four Game . . . . . . . . . . . . . . . . . . . 201
10 Simple Story Driven Modeling 203
10.1 The Study-Right University doAssignments . . . . . . . . . . . 203
10.2 The Study-Right University findPath . . . . . . . . . . . . . . . 212
10.3 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
11 SDM of GUI Applications 219
11.1 Storyboard and Behavior Modeling . . . . . . . . . . . . . . . . 235
11.2 Using a GUI Construction Toolkit . . . . . . . . . . . . . . . . 243
11.3 Testing Graphical User Interfaces . . . . . . . . . . . . . . . . . 251
11.4 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
11.4.1 Mau Mau . . . . . . . . . . . . . . . . . . . . . . . . . 254
11.4.2 Battleships . . . . . . . . . . . . . . . . . . . . . . . . 255
11.4.3 Mancala . . . . . . . . . . . . . . . . . . . . . . . . . . 255
11.4.4 Mensch Ärgere Dich Nicht . . . . . . . . . . . . . . . . 255
11.4.5 Towers of Hanoi . . . . . . . . . . . . . . . . . . . . . 255
11.4.6 ATM Money Withdrawal . . . . . . . . . . . . . . . . . 255
11.4.7 Borrowing Electronic Books from Library . . . . . . . 255
11.4.8 Trouble Ticket System . . . . . . . . . . . . . . . . . . 255
11.4.9 Webshop . . . . . . . . . . . . . . . . . . . . . . . . . 255
11.4.10 Connect Four Game . . . . . . . . . . . . . . . . . . . 255
III Scaling Up 257
12 SDM for concurrent applications 259
12.1 Multiple Threads to Keep Your GUI Responsive . . . . . . . . . 261
12.2 A Basic Chat Program . . . . . . . . . . . . . . . . . . . . . . 271
12.3 Exercise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281
12.3.1 Collaborative Whiteboard . . . . . . . . . . . . . . . . 281
12.3.2 Client Server Chat . . . . . . . . . . . . . . . . . . . . 283
12.3.3 Multi Player Versions of Our Exercise Applications . . 284
13 Story Driven Modeling 285
13.1 Iterative Refinement . . . . . . . . . . . . . . . . . . . . . . . 285
13.2 SDM with Graphical User Interfaces . . . . . . . . . . . . . . . 287
13.3 SDM with Customers . . . . . . . . . . . . . . . . . . . . . . . 289
13.3.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . 293
13.3.2 Writing business software for customers . . . . . . . . . 298
13.4 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
13.4.1 Kanban Board . . . . . . . . . . . . . . . . . . . . . . 300
13.4.2 Assignment Management System . . . . . . . . . . . . 300
13.4.3 Key Administrative App . . . . . . . . . . . . . . . . . 300
14 Yes, It Scales 303
14.1 More Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
14.2 More Classes, More Algorithms . . . . . . . . . . . . . . . . . 306
14.3 Design Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . 309
14.4 More Installations . . . . . . . . . . . . . . . . . . . . . . . . . 310
14.5 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
15 SDM of Embedded Applications 315
15.1 What is an Embedded System? . . . . . . . . . . . . . . . . . . 316
15.2 Example: LEGO Mindstorms NXT Robotics System . . . . . . 319
15.3 Example: Android Platform (for Robotics) . . . . . . . . . . . . 320
15.4 Developing for Arduino . . . . . . . . . . . . . . . . . . . . . . 321
15.5 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322


I Object Models

1 Introduction
If you would ask us, whether this is just another book about modeling, we would probably feel inclined to say: yes and no.
Yes, it is a lot about modeling, but no, it is also about programming, methodological software design, and rapid prototyping via methods from model driven engineering.
It will also be one of the first complete references and teaching guides for Story Driven Modeling.
Story Driven Modeling is an agile software development method using objects and scenarios and special modeling steps to facilitate system analysis and design, [34, 2 l, 20].
Most parts of this book can be done with pencil and paper and with standard UML tools and standard software development environments.
However, some steps are best supported by the rapid prototyping tool Fujaba [5] or the Story Driven Modeling library SDMLib [I0].
The title of this book does not include Object Oriented Modeling on purpose.
Object Orientation, Object Oriented Design, Object Oriented Analysis, and other object oriented methods all refer somehow to class diagrams and inheritance.
Instead of this, we will actively use objects for modeling, analysis, and design.
We will learn to think in objects.
This book is foremost planned to be a textbook for software modeling courses.
It offers a very interactive and agile approach to modern software design.
ln this book, we introduce the Objects First principle which is the foundation of the Story Driven Modeling development method.
This is not to be mistaken with an object oriented development method.
You will see that the Object First method slightly differs from traditional object oriented methods.
With this book, we address a majority of readers dealing with or wanting to learn sofiware development.
This includes teachers and students for introduction to Object Orientation, Systems Modeling, Object Oriented Design, or Model Driven Engineering.
This book should also be insightful for people interested in modeling and program design and beginning programmers.
We expect from.

1.1 Why Model?

Think for a minute, what was the biggest software project you have been involved in?
How many lines of code did it have?
How long have people been working on it?
If things took long, why did they take this much time?
Usually, people thinking about these questions will recall some communication problems in the process of developing a specific program.
These communication problems occur talking to the customer and between the programmers and managers.
Also, it should be observed that these problems are growing the bigger the project is.
As the title of this book includes “Modeling�, modeling might be an answer to some of the problems we just discovered.
However, why should we model, when we are all great programmers?
This is also a good question to ask to students to get them thinking.
How would you answer this question?
If you were supposed to understand it, we wouldn’t call it code".
- from a Federal Express promotion, reported by IS Survivalist Matthew 0.
Writing code already means that we create an artifact, which is not easy to understand, which is encrypted in a way that makes it less accessible for human understanding.
It is obvious that showing the problem in a particular context, omitting some of the machine specific details, will help to understand this view better and therefore foster communication.
Models can show connections, relations, and context at once.
This can help us to see and analyze risks and costs.
Many definitions of the temi “model� (in the context of software) are related to a system.
Such as given by Bezivin et al. in [I8]: “A model is a simplification of a system built with an intended goal in mind.
The model should be able to answer questions in place of the actual system". 
or given by Seidewitz in [33]: "A model is a set of statements about some system under study [SUS].
Here, statement means expression about the SUS.
A definition focusing on aspects of a reality rather than systems is provided by Pohl in [3l]: “A model is an abstracting image of an existing or fictitious reality".