Excerpts

The Unified Modeling Language (UML) is a graphical language for visualizing, specifying, constructing, and documenting the artifacts of a software-intensive system. The UML gives you a standard way to write a system's blueprints, covering conceptual things such as business processes and system functions, as well as concrete things such as classes written in a specific programming language, database schemas, and reusable software components. This book teaches you how to use the UML effectively. This book covers UML version 2.0. Goals In this book, you will Learn what the UML is, what it is not, and why the UML is relevant to the process of developing software-intensive systems. Master the vocabulary, rules, and idioms of the UML and, in general, learn how to "speak" the language effectively. Understand how to apply the UML to solve a number of common modeling problems. The user guide provides a reference to the use of specific UML features. However, it is not intended to be a comprehensive reference manual for the UML; that is the focus of another book, The Unified Modeling Language Reference Manual, Second Edition (Rumbaugh, Jacobson, Booch, Addison-Wesley, 2005).The user guide describes a development process for use with the UML. However, it is not intended to provide a complete reference to that process; that is the focus of yet another book, The Unified Software Development Process (Jacobson, Booch, Rumbaugh, Addison-Wesley, 1999). Finally, this book provides hints and tips for using the UML to solve a number of common modeling problems, but it does not teach you how to model. This is similar to a user guide for a programming language that teaches you how to use the language but does not teach you how to program. Audience The UML is applicable to anyone involved in the production, deployment, and maintenance of software. The user guide is primarily directed to members of the development team who create UML models. However, it is also suitable to those who read them, working together to understand, build, test, and release a software-intensive system. Although this encompasses almost every role in a software development organization, the user guide is especially relevant to analysts and end users (who specify the required structure and behavior of a system), architects (who design systems that satisfy those requirements), developers (who turn those architectures into executable code), quality assurance personnel (who verify and validate the system's structure and behavior), librarians (who create and catalogue components), and project and program managers (who generally wrestle with chaos, provide leadership and direction, and orchestrate the resources necessary to deliver a successful system). The user guide assumes a basic knowledge of object-oriented concepts. Experience in an object-oriented programming language or method is helpful but not required. How to Use This Book For the developer approaching the UML for the first time, the user guide is best read linearly. You should pay particular attention to Chapter 2, which presents a conceptual model of the UML. All chapters are structured so that each builds upon the content of the previous one, thus forming a linear progression.For the experienced developer seeking answers to common modeling problems using the UML, this book can be read in any order. You should pay particular attention to the common modeling problems presented in each chapter. Organization and Special Features The user guide is organized into seven parts: Part 1Getting Started Part 2Basic Structural Modeling Part 3Advanced Structural Modeling Part 4Basic Behavioral Modeling Part 5Advanced Behavioral Modeling Part 6Architectural Modeling Part 7Wrapping Up The user guide contains two appendices: a summary of the UML notation and a summary of the Rational Unified Process. A glossary of common terms is also provided. An index follows. Each chapter addresses the use of a specific UML feature, and most are organized into the following four sections: Getting Started Terms and Concepts Common Modeling Techniques Hints and Tips The third section introduces and then solves a set of common modeling problems. To make it easy for you to browse the guide in search of these use cases for the UML, each problem is identified by a distinct heading, as in the following example. Modeling Architectural Patterns Each chapter begins with a summary of the features it covers, as in the following example. In this chapter Active objects, processes, and threads Modeling multiple flows of control Modeling interprocess communication Building thread-safe abstractions Similarly, parenthetical comments and general guidance are set apart as notes, as in the following example. Note: Abstract operations map to what C++ calls pure virtual operations; leaf operations in the UML map to C++ nonvirtual operations. The UML is semantically rich. Therefore, a presentation about one feature may naturally involve another. In such cases, cross references are provided in the left margin, as on this page. Blue highlights are used in figures to indicate explanations about a model, as opposed to the model itself, which is always shown in black. Code is distinguished by displaying it in a monospace font, as in this example . Acknowledgement. The authors wish to thank Bruce Douglass, Per Krol, and Joaquin Miller for their assistance in reviewing the manuscript of the second edition. A Brief History of the UML The first object-oriented language is generally acknowledged to be Simula-67, developed by Dahl and Nygaard in Norway in 1967. This language never had a large following, but its concepts were a major inspiration for later languages. Smalltalk became widely available in the early 1980s, followed by other object-oriented languages such as Objective C, C++, and Eiffel in the late 1980s. Object-oriented modeling languages appeared in the 1980s as methodologists, faced with a new genre of object-oriented programming languages and increasingly complex applications, began to experiment with alternative approaches to analysis and design. The number of object-oriented methods increased from fewer than 10 to more than 50 during the period between 1989 and 1994. Many users of these methods had trouble finding a modeling language that met their needs completely, thus fueling the so-called method wars. A few methods gained prominence, including Booch's method, Jacobson's OOSE (Object-Oriented Software Engineering), and Rumbaugh's OMT (Object Modeling Technique). Other important methods included Fusion, Shlaer-Mellor, and Coad-Yourdon. Each of these was a complete method, although each was recognized as having strengths and weaknesses. In simple terms, the Booch method was particularly expressive during the design and construction phases of projects; OOSE provided excellent support for use cases as a way to drive requirements capture, analysis, and high-level design; and OMT was most useful for analysis and data-intensive information systems. A critical mass of ideas started to form by the mid 1990s when Grady Booch (Rational Software Corporation), James Rumbaugh (General Electric), Ivar Jacobson (Objectory), and others began to adopt ideas from each other's methods, which collectively were becoming recognized as the leading object-oriented methods worldwide. As the primary authors of the Booch, OMT, and OOSE methods, we were motivated to create a unified modeling language for three reasons. First, our methods were already evolving toward each other independently. It made sense to continue that evolution together rather than apart, eliminating the potential for any unnecessary and gratuitous differences that would further confuse users. Second, by unifying our methods, we could bring some stability to the object-oriented marketplace, allowing projects to settle on one mature modeling language and letting tool builders focus on delivering more useful features. Third, we expected that our collaboration would yield improvements for all three earlier methods, helping us to capture lessons learned and to address problems that none of our methods previously handled well. As we began our unification, we established three goals for our work: To model systems, from concept to executable artifact, using object- oriented techniques To address the issues of scale inherent in complex, mission-critical systems To create a modeling language usable by both humans and machines Devising a language for use in object-oriented analysis and design is not unlike designing a programming language. First, we had to constrain the problem: Should the language encompass requirements specification? Should the language be sufficient to permit visual programming? Second, we had to strike a balance between expressiveness and simplicity. Too simple a language would limit the breadth of problems that could be solved; too complex a language would overwhelm the mortal developer. In the case of unifying existing methods, we also had to be sensitive to the installed base. Make too many changes and we would confuse existing users; resist advancing the language and we would miss the opportunity to engage a much broader set of users and to make the language simpler. The UML definition strives to make the best trade-offs in each of these areas. The UML effort started officially in October 1994 when Rumbaugh joined Booch at Rational. Our project's initial focus was the unification of the Booch and OMT methods. The version 0.8 draft of the Unified Method (as it was then called) was released in October 1995. Around the same time, Jacobson joined Rational and the scope of the UML project was expanded to incorporate OOSE. Our efforts resulted in the release of the UML version 0.9 documents in June 1996. Throughout 1996, we invited and received feedback from the general software engineering community. During this time, it also became clear that many software organizations saw the UML as strategic to their business. We established a UML consortium, with several organizations willing to dedicate resources to work toward a strong and complete UML definition. Those partners contributing to the UML 1.0 definition included Digital Equipment Corporation, Hewlett-Packard, I-Logix, Intellicorp, IBM, ICON Computing, MCI Systemhouse, Microsoft, Oracle, Rational, Texas Instruments, and Unisys. This collaboration resulted in the UML 1.0, a modeling language that was well-defined, expressive, powerful, and applicable to a wide spectrum of problem domains. Mary Loomis was instrumental in convincing the Object Management Group (OMG) to issue a request for proposals (RFP) for a standard modeling language. UML 1.0 was offered for standardization to the OMG in January 1997 in response to their RFP. Between January 1997 and July 1997, the original group of partners was expanded to include virtually all of the other submitters and contributors of the original OMG response, including Andersen Consulting, Ericsson, ObjecTime Limited, Platinum Technology, PTech, Reich Technologies, Softeam, Sterling Software, and Taskon. A semantics task force was formed, led by Cris Kobryn of MCI Systemhouse and administered by Ed Eykholt of Rational, to formalize the UML specification and to integrate the UML with other standardization efforts. A revised version of the UML (version 1.1) was offered to the OMG for standardization in July 1997. In September 1997, this version was accepted by the OMG Analysis and Design Task Force (ADTF) and the OMG Architecture Board and then put up for vote by the entire OMG membership. UML 1.1 was adopted by the OMG on November 14, 1997. For several years, UML was maintained by an OMG Revision Task Force, which produced versions 1.3, 1.4, and 1.5. From 2000 to 2003, a new and expanded set of partners produced an updated specification of UML, version 2.0. This version was reviewed for a year by a Finalization Task Force (FTF) headed by Bran Selic of IBM, and the official version of UML 2.0 was adopted by the OMG in early 2005. UML 2.0 is a major revision of UML 1 and includes a large number of additional features. In addition, many changes were made to previous constructs based on experience with the previous version. The actual UML specification documents are found on the OMG Website at www.omg.org . UML is the work of a large number of individuals, and the ideas in it come from a wide range of previous works. It would be a major historical research project to reconstruct a complete list of sources, and even more difficult to identify the many predecessors who have influenced UML in manners large and small. As with all scientific research and engineering practice, UML is a small hill atop a large mountain of previous experience. Excerpted from The Unified Modeling Language User Guide by Grady Booch, James Rumbaugh, Ivar Jacobson All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.