Praise for SysML Distilled“In keeping with the outstanding tradition of Addison-Wesley’s technical publications, Lenny Delligatti’s SysML Distilled does not disappoint.Lenny has done a masterful job of capturing the spirit of OMG SysMLas a practical, standards-based modeling language to help systems engineers address growing system complexity. This book is loaded withmatter-of-fact insights, starting with basic MBSE concepts to distinguishing the subtle differences between use cases and scenarios to illumination on namespaces and SysML packages, and even speaks to someof the more esoteric SysML semantics such as token flows.”— Jeff Estefan, Principal Engineer, NASA’s Jet Propulsion Laboratory“The power of a modeling language, such as SysML, is that it facilitatescommunication not only within systems engineering but across disciplines and across the development life cycle. Many languages have thepotential to increase communication, but without an effective guide,they can fall short of that objective. In SysML Distilled, Lenny Delligatticombines just the right amount of technology with a common-senseapproach to utilizing SysML toward achieving that communication.Having worked in systems and software engineering across many domains for the last 30 years, and having taught computer languages,UML, and SysML to many organizations and within the college setting,I find Lenny’s book an invaluable resource. He presents the conceptsclearly and provides useful and pragmatic examples to get you off theground quickly and enables you to be an effective modeler.”— Thomas W. Fargnoli, Lead Member of theEngineering Staff, Lockheed Martin“This book provides an excellent introduction to SysML. Lenny Delligatti’s explanations are concise and easy to understand; the exampleswell thought out and interesting.”— Susanne Sherba, Senior Lecturer, Department ofComputer Science, University of Denver“Lenny hits the thin line between a reference book for SysML to lookup elements and an entertaining book that could be read in its entiretyto learn the language. A great book in the tradition of the famous UMLDistilled.”— Tim Weilkiens, CEO, oose

“More informative than a PowerPoint, less pedantic than an OMG Profile Specification, SysML Distilled offers practicing systems engineersjust the right level of the motivation, concepts, and notation of pureOMG SysML for them to attain fluency with this graphical language forthe specification and analysis of their practical and complex systems.”— Lonnie VanZandt, chief architect, No Magic, Inc.“Delligatti’s SysML Distilled is a most aptly named book; it representsthe distillation of years of experience in teaching and using SysML inindustrial settings. The author presents a very clear and highly read able view of this powerful but complex modeling language, illustratingits use via easy-to-follow practical examples. Although intended primarily as an introduction to SysML, I have no doubt that it will alsoserve as a handy reference for experienced practitioners.”— Bran Selic, president, Malina Software Corp.“SysML is a rather intimidating modeling language, but in this bookLenny makes it really easy to understand, and the advice throughoutthe book will help practitioners avoid numerous pitfalls and help themgrasp and apply the core elements and the spirit of SysML. If you areplanning on applying SysML, this is the book for you!”— Celso Gonzalez, senior developer, IBM Rational“SysML Distilled is a great book for engineers who are starting to delveinto model-based systems engineering. The space system examplescapture the imagination and express the concepts in a simple but effective way.”— Matthew C. Hause, chief consulting engineer,Atego and chair, OMG UPDM Group“I’ve been deeply involved with OMG since the 1990s, but my professional needs have not often taken me into the SysML realm. So I thoughtI’d be a good beta tester for Lenny’s book. To my delight, I learned agreat deal reading through it, and I know you will too.”— Doug Tolbert, distinguished engineer, Unisys, and member,OMG Board of Directors and Architecture Board

“SysML Distilled provides a clear and comprehensive description of thelanguage component of model-based systems engineering, while offering suggestions for where to find information about the tool and methodology components. There is evidence throughout the book that theauthor has a deep understanding of SysML and its application in a system development process. I will definitely be using this as a textbook inthe MBSE courses I teach.”— J. D. Baker, OCUP, OCSMP, member of theOMG Architecture Board“SysML Distilled is the desktop companion that many SysML modelershave needed for their bookshelves. Lenny has the experience and certifications to help you through your day-to-day modeling questions.This book is not a tutorial, nor is it the encyclopedic compendium of allthings SysML. If you model using SysML, this will become your dailycompanion, as it is meant to be used regularly. I believe your copy willsoon be dog-eared, with sticky notes throughout.”— Dr. Robert Cloutier, Stevens Institute of Technology“SysML is utilized today in a wide range of applications, includingdeep space robotic spacecraft and down-to-earth agricultural equipment. This book concisely presents SysML in a manner that is both refreshingly accessible for new learners and quite handy for seasonedpractitioners.”— Russell Peak, MBSE branch chief,Aerospace Systems Design Lab, Georgia Tech“SysML Distilled is a wonderfully written, knowledgeable, and conciseaddition to systems modeling literature. The lucid explanations lead anewcomer by the hand into modeling reasonably complex systems,and the wealth and depth of the coverage of the most-used aspects ofthe SysML modeling language stretch to even enabling advanced intermediate depictions of most systems. It also serves as a handy reference.Kudos to Mr. Delligatti for gifting the world with this very approach able view of systems modeling.”— Bobbin Teegarden, CTO/chief architect,OntoAge and Board Member, No Magic, Inc.

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SysML Distilled

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SysML DistilledA Brief Guideto the SystemsModeling LanguageLenny DelligattiUpper Saddle River, NJ Boston Indianapolis San FranciscoNew York Toronto Montreal London Munich Paris MadridCapetown Sydney Tokyo Singapore Mexico City

Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and the publisher was aware of a trademark claim, thedesignations have been printed with initial capital letters or in all capitals.The author and publisher have taken care in the preparation of this book, but make no expressed or impliedwarranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for incidentalor consequential damages in connection with or arising out of the use of the information or programs containedherein.The publisher offers excellent discounts on this book when ordered in quantity for bulk purchases or specialsales, which may include electronic versions and/or custom covers and content particular to your business,training goals, marketing focus, and branding interests. For more information, please contact:U.S. Corporate and Government Sales(800) [email protected] sales outside the United States, please contact:International [email protected] us on the Web: of Congress Cataloging-in-Publication DataDelligatti, Lenny.SysML distilled : a brief guide to the systems modeling language / Lenny Delligatti.pages cmIncludes bibliographical references and index.ISBN-13: 978-0-321-92786-6 (paperback : alk. paper)ISBN-10: 0-321-92786-9 (paperback : alk. paper)1. Systems engineering—Data processing. 2. Engineering systems—Computersimulation. 3. SysML (Computer science) I. Title.TA168.D44 2014620.00285'5133—dc232013035922Copyright 2014 Pearson Education, Inc.All rights reserved. Printed in the United States of America. This publication is protected by copyright, and permission must be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system,or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise. Toobtain permission to use material from this work, please submit a written request to Pearson Education, Inc.,Permissions Department, One Lake Street, Upper Saddle River, New Jersey 07458, or you may fax your requestto (201) 236-3290.ISBN-13: 978-0-321-92786-6ISBN-10:0-321-92786-9Text printed in the United States on recycled paper at RR Donnelley in Crawfordsville, Indiana.First printing, November 2013

This book is dedicated to my wife, Natalie, and my children,Aidan and Noelle—my greatest blessings . . . and myreasons for enduring the many late nights of writing.

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ContentsForeword by Rick SteinerxviiForeword by Richard SoleyxixPrefacexxvAcknowledgmentsxxxiAbout the AuthorChapter 1 Overview of Model-Based Systems Engineering1.1 What Is MBSE?1.2 The Three Pillars of MBSE1.3 The Myth of MBSEChapter 2 Overview of the Systems Modeling Language2.1 What SysML Is—and Isn’t2.2 Yes, SysML Is Based on UML—but You Can Startwith SysML2.3 SysML Diagram Overview2.4 General Diagram ConceptsChapter 3 Block Definition Diagrams3. Should You Create a BDD?The BDD FrameBlocksAssociations: Another Notation for a 314172323242426444952xi

xiiContents3.8 Actors3.9 Value Types3.10 Constraint Blocks3.11 Comments53555759Chapter 4 Internal Block Diagrams634.1 Purpose4.2 When Should You Create an IBD?4.3 Blocks, Revisited4.4 The IBD Frame4.5 BDDs and IBDs: Complementary Views of a Block4.6 Part Properties4.7 Reference Properties4.8 Connectors4.9 Item Flows4.10 Nested Parts and ReferencesChapter 5 Use Case Diagrams5.1 Purpose5.2 When Should You Create a Use Case Diagram?5.3 Wait! What’s a Use Case?5.4 The Use Case Diagram Frame5.5 Use Cases5.6 System Boundary5.7 Actors5.8 Associating Actors with Use Cases5.9 Base Use Cases5.10 Included Use Cases5.11 Extending Use CasesChapter 6 Activity Diagrams6.1 Purpose6.2 When Should You Create an Activity 87898990

Contents6.3 The Activity Diagram Frame6.4 A Word about Token Flow6.5 Actions: The Basics6.6 Object Nodes6.7 Edges6.8 Actions, Revisited6.9 Control Nodes6.10 Activity Partitions: Allocating Behaviorsto StructuresChapter 7 Sequence Diagrams7.1 Purpose7.2 When Should You Create a Sequence Diagram?7.3 The Sequence Diagram Frame7.4 Lifelines7.5 Messages7.6 Destruction Occurrences7.7 Execution Specifications7.8 Constraints7.9 Combined Fragments7.10 Interaction UsesChapter 8 State Machine Diagrams8. Should You Create a State Machine Diagram?The State Machine Diagram FrameStatesTransitionsPseudostatesRegionsChapter 9 Parametric Diagrams9.1 Purpose9.2 When Should You Create a Parametric 9141144151155155156156158162171173177177178xiii

xivContents9., RevisitedThe Parametric Diagram FrameConstraint PropertiesConstraint ParametersValue PropertiesBinding ConnectorsChapter 10 Package n Should You Create a Package Diagram?The Package Diagram FrameNotations for Namespace ContainmentDependencies between PackagesImporting PackagesSpecialized PackagesShades of Gray: Are You Looking at a PackageDiagram or a Block Definition Diagram?Chapter 11 Requirements Diagrams11.111.211.311.411.511.611.7PurposeWhen Should You Create a Requirements Diagram?The Requirements Diagram FrameRequirementsRequirements RelationshipsNotations for Requirements RelationshipsRationaleChapter 12 Allocations: Cross-Cutting Relationships12.112.212.312.412.5PurposeThere’s No Such Thing as an Allocation DiagramUses for Allocation RelationshipsNotations for Allocation 216219224

Contents Appendix A: SysML Notation Desk Reference227Appendix B: Changes between SysML Versions245Bibliography253Index255xv

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Foreword by Rick SteinerSystems engineering is not an easy subject to teach. Earlier in my career, I was emphatically told that systems engineering could not betaught in a classroom and that it could only be learned through experience. While that hasn’t proven to be true, there are certainly conceptswithin the practice of systems engineering that are both subtle andarcane.Expressing these concepts in models demands a suitably robustlanguage, which is why a dedicated group of us began development ofwhat would become SysML in early 2002. We attempted to be parsimonious and direct when designing the language, specifically targeting itfor use by practicing systems engineers. I’m convinced that the resulting language is both flexible and useful, and I am gratified that it hasemerged as a dominant standard for communicating systems-relatedideas.Just like the practice of systems engineering, however, SysML hasproven difficult to teach effectively. The scope of systems engineeringis remarkably broad, and even though SysML is a relatively compactlanguage, students frequently get overwhelmed with its complexity.Resources for learning SysML and model-based systems engineeringhave until recently been rather limited, but it’s getting better. FormalMBSE and SysML courses are now regularly being taught through several university or extension catalogs, and at least one comprehensivetextbook is now available.An engineer or manager who wants to casually learn the basics ofSysML isn’t likely to want to take a class. An advanced