Cambridge University Press
0521616786 - The Elements of UML^TM 2.0 Style - by Scott W. Ambler
Frontmatter/Prelims

The Elements
of
UML^TM 2.0 Style

For Beverley

The Elements
of
UML^TM 2.0 Style

Scott W. Ambler

CAMBRIDGE UNIVERSITY PRESS
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Cambridge University Press
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Information on this title: www.cambridge.org/9780521616782

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and to the provisions of relevant collective licensing agreements,
no reproduction of any part may take place without
the written permission of Cambridge University Press.

First published 2005

Printed in the United States of America

A catalog record for this publication is available from the British Library.

Library of Congress Cataloging in Publication Data

Ambler, Scott W., 1966–
The elements of UML 2.0 style / Scott W. Ambler.
p. cm.
Includes bibliographical references and index.
ISBN 0-521-61678-6 (pbk.)
1. UML (Computer science). 2. Computer software – Development. I. Title.
QA76.76.D47A4258 2005
005.1 – dc22 2005003160

ISBN-13 978-0-521-61678-2 paperback
ISBN-10 0-521-61678-6 paperback

Cambridge University Press has no responsibility for the persistence or accuracy of URLs for external or third-party Internet Web sites referred to in this book and does not guarantee that any content on such Web sites is, or will remain, accurate or appropriate.

Preface		ix
Purpose		ix
Features		x
Audience		x
Assumptions		x
Acknowledgments		xi
1.	Introduction	1
1.1	Organization of This Book	2
2.	General Diagramming Guidelines	4
2.1	Readability Guidelines	4
2.2	Simplicity Guidelines	8
2.3	Naming Guidelines	11
2.4	General Guidelines	12
3.	Guidelines for Common UML Modeling Elements	15
3.1	Guidelines for UML Notes	15
3.2	Guidelines for UML Stereotypes	18
3.3	Guidelines for UML Frames	21
3.4	Guidelines for UML Interfaces	24
4.	UML Use-Case Diagrams	33
4.1	Use-Case Guidelines	33
4.2	Actor Guidelines	35
4.3	Relationship Guidelines	38
4.4	System Boundary Box Guidelines	45
5.	UML Class Diagrams	47
5.1	General Guidelines	47
5.2	Class Style Guidelines	51
5.3	Relationship Guidelines	59
5.4	Association Guidelines	64
5.5	Inheritance Guidelines	68
5.6	Aggregation and Composition Guidelines	70
6.	UML Package Diagrams	73
6.1	Class Package Diagram Guidelines	73
6.2	Use-Case Package Diagram Guidelines	76
6.3	Packages	78
7.	UML Sequence Diagrams	80
7.1	General Guidelines	81
7.2	Guidelines for Lifelines	86
7.3	Message Guidelines	89
7.4	Guidelines for Return Values	91
8.	UML Communication Diagrams	94
8.1	General Guidelines	95
8.2	Message Guidelines	98
8.3	Link Guidelines	100
9.	UML State Machine Diagrams	103
9.1	General Guidelines	103
9.2	State Guidelines	105
9.3	Substate Modeling Guidelines	106
9.4	Transition and Action Guidelines	108
9.5	Guard Guidelines	111
10.	UML Activity Diagrams	113
10.1	General Guidelines	113
10.2	Activity Guidelines	116
10.3	Decision Point and Guard Guidelines	116
10.4	Parallel Flow Guidelines	121
10.5	Activity Partition (Swim Lane) Guidelines	122
10.6	Action-Object Guidelines	128
11.	UML Component Diagrams	132
11.1	Component Guidelines	132
11.2	Dependency and Inheritance Guidelines	136
12.	UML Deployment Diagrams	139
12.1	General Guidelines	140
12.2	Node and Component Guidelines	144
12.3	Dependency and Communication-Association Guidelines	146
13.	UML Object Diagrams	148
14.	UML Composite Structure Diagrams	150
15.	UML Interaction Overview Diagrams	153
16.	UML Timing Diagrams	157
16.1	General Guidelines	157
16.2	Axis Guidelines	159
16.3	Time Guidelines	160
17.	Agile Modeling	162
17.1	Values	162
17.2	Principles	162
17.3	Practices	164
Bibliography		165
Index		169

Preface

Models are used by professional developers to communicate their work to project stakeholders and to other developers. The Unified Modeling Language (UML) has been an important part of the software development landscape since its introduction in 1997. We’ve seen the UML evolve over the years and it is now into its 2.x series of releases. Modeling style, however, has remained constant and will continue to do so. By understanding and following these common modeling style guidelines, you can improve the effectiveness of your models.

I’ve updated this book to include the new diagrams in UML 2, to use the terminology of UML 2, and to include hand-drawn diagrams. The vast majority of models are drawn on whiteboards and I think that it’s time that modeling books, including this one, reflect that reality.

Purpose

This book describes a collection of standards, conventions, and guidelines for creating effective UML diagrams. They are based on sound, proven principles that will lead to diagrams that are easier to understand and work with.

These simple, concise guidelines, if applied consistently, will be an important first step in increasing your productivity as a modeler.

Features

This guide attempts to emulate Strunk and White’s (1979) seminal text, The Elements of Style, which lists a set of rules describing the proper application of grammatical and compositional forms in common use within the written English language.

Using a similar style of presentation, this book defines a set of rules for developing high-quality UML diagrams. In doing so, this guide

■ employs existing standards defined by the Object Management Group (OMG) whenever possible,

■ provides a justification for each rule, and

■ presents standards based on real-world experience and proven principles.

Audience

This guide targets information technology (IT) professionals who are interested in

■ creating effective UML diagrams,

■ increasing their productivity, and

■ working as productive members of a software development team.

Assumptions

In this book I make several assumptions:

■	You understand the basics of the UML and modeling. If not, then I suggest UML Distilled (Fowler 2004) if you are looking for a brief overview of the UML, or better yet The Object Primer, third edition (Ambler 2004) for a more comprehensive discussion. UML Distilled is a great book but is limited to the UML; The Object Primer, third edition, on the other hand, goes beyond the UML where needed, for example, to include user interface, Java, and database development issues. It also covers agile software development techniques in detail.
■	You are looking for style guidelines, not design guidelines. If not, then I suggest the book Object-Oriented Design Heuristics (Riel 1996).
■	Your focus is on business application development. Although these guidelines also apply to real-time development, all of the examples are business application–oriented, simplifications of actual systems that I have built in the past.
■	You belong to a Western culture. Many of the layout guidelines are based on the Western approach to reading—left to right and top down. People in other cultures will need to modify these guidelines as appropriate.

Acknowledgments

The following people have provided valuable input into the development and improvement of this text: James Bielak, Chris Britton, Larry Brunelle, Lauren Cowles, Beverley Dawe, Caitlin Doggart, Doug English, Jessica Farris, Scott Fleming, Mark Graybill, Alvery Grazebrook, Jesper R. Jensen, Jon Kern, Kirk W. Knoernschild, Hubert Matthews, Les Munday, Sabine Noack, Paul Oldfield, Marco Peters, Scott W. Preece, Neil Pitman, Edmund Schweppe, Leo Tohill, Tim Tuxworth, Michael Vizdos, and Robert White.