Goals
This book is intended to be a complete and useful reference to the Unified Modeling Language (UML) for the developer, architect, project manager, system engineer, programmer, analyst, contracting officer, customer, and anyone else who needs to specify, design, build, or understand complex software systems. It provides a full reference to the concepts and constructs of UML, including their semantics, syntax, notation, and purpose. It is organized to be a convenient but thorough reference for the working professional developer. It also attempts to provide additional detail about issues that may not be clear from the standard documents and to provide a rationale for many decisions that went into the UML.
This book is not intended as a guide to the UML standards documents or to the internal structure of the metamodel contained in them. The details of the metamodel are of interest to methodologists and UML tool builders, but most other developers have little need for the arcane details of the Object Management Group (OMG) documents. This book provides all the details of UML that most developers need; in many cases, it makes information explicit that must otherwise be sought between the lines of the original documents. For those who do wish to consult the source documents, they are included on the accompanying CD.
This book is intended as a reference for those who already have some understanding of object-oriented technology. For beginners, the original books by us and by other authors are listed in the bibliography; although some of the notation has changed, books such as [Rumbaugh-91], [Booch-94], [Jacobson-92], and [Meyer-88] provide an introduction to object-oriented concepts that is still valid and therefore unnecessary to duplicate here. For a tutorial introduction to UML that shows how to model a number of common problems, see The Unified Modeling Language User Guide [Booch-99]. Those who already know an object-oriented method, such as OMT, Booch, Objectory, Coad-Yourdon, or Fusion, should be able to read the Reference Manual and use it to understand UML notation and semantics; to learn UML quickly, they may nevertheless find it useful to read the User Guide.
UML does not require a particular development process, and this book does not describe one. Although UML may be used with a variety of development processes, it was designed to support an iterative, incremental, use-case–driven process with a strong architectural focus--the kind we feel is most suitable for the development of modern, complex systems. The Unified Software Development Process [Jacobson-99] describes the kind of process we believe complements the UML and best supports software development.
Outline of the Book
The UML Reference Manual is organized into three parts: an overview of UML history and of modeling, a survey of UML concepts, and an alphabetical encyclopedia of UML terms and concepts.
The first part is a survey of UML--its history, purposes, and uses--to help you understand the origin of UML and the need it tries to fill.
The second part is a brief survey of UML views so that you can put all the concepts into perspective. The survey provides a brief overview of the views UML supports and shows how the various constructs work together. This part begins with an example that walks through various UML views and then contains one chapter for each kind of UML view. This survey is not intended as a full tutorial or as a comprehensive description of concepts. It serves mainly to summarize and relate the various UML concepts and provides starting points for detailed readings in the encyclopedia.
The third part contains the reference material organized for easy access to each topic. The bulk of the book is an alphabetical encyclopedia of all of the concepts and constructs in UML. Each UML term of any importance has its own entry in the encyclopedia. The encyclopedia is meant to be complete; therefore, everything in the concept overview in Part 2 is repeated in more detail in the encyclopedia. The same or similar information has sometimes been included in multiple encyclopedia articles so that the reader can conveniently find it.
The reference part also contains an alphabetic list of UML standard elements. A standard element is a feature predefined using the UML extensibility mechanisms. The standard elements are extensions that are felt to be widely useful.
Appendices show the UML metamodel, a summary of UML notation, and some standard sets of extensions for particular domains. There is a brief bibliography of major object-oriented books, but no attempt has been made to include a comprehensive citation of sources of ideas for UML or other approaches. Many of the books in the bibliography contain excellent lists of references to books and journal articles for those interested in tracking the development of the ideas.
Encyclopedia Article Formatting Conventions
The encyclopedia part of the book is organized as an alphabetical list of entries, each describing one concept in some detail. The articles represent a flat list of UML concepts at various conceptual levels. A high-level concept typically contains a summary of its subordinate concepts, each of which is fully described in a separate article. The articles are highly cross-referenced. This flat encyclopedia organization permits the description of each concept to be presented at a fairly uniform level of detail, without constant shifts in level for the nested descriptions that would be necessary for a sequential presentation. The hypertext format of the document should also make it convenient for reference. It should not be necessary to use the index much; instead go directly to the main article in the encyclopedia for any term of interest and follow cross-references. This format is not necessarily ideal for learning the language; beginners are advised to read the overview description of UML found in Part 2 or to read introductory books on UML, such as the UML User Guide [Booch-99].
Encyclopedic articles have the following divisions, although not all divisions appear in all articles.
Brief definition
The name of the concept appears in boldface, set to the left of the body of the article. A brief definition follows in normal type. This definition is intended to capture the main idea of the concept, but it may simplify the concept for concise presentation. Refer to the main article for precise semantics.
Semantics
This section contains a detailed description of the meaning of the concept, including constraints on its uses and its execution consequences. Notation is not covered in this section, although examples use the appropriate notation. General semantics are given first. For concepts with subordinate structural properties, a list of the properties follows the general semantics, often under the subheading Structure. In most cases, the properties appear as a table in alphabetical order by property name, with the description of each property on the right. If a property has a brief enumerated list of choices, they may be given as an indented sublist. In more complicated cases, the property is given its own article to avoid excessive nesting. When properties require more explanation than permitted by a table, they are described in normal text with run-in headers in boldface italics. In certain cases, the main concept is best described under several logical subdivisions rather than one list. In such cases, additional sections follow or replace the Structure subsection. Although several organizational mechanisms have been used, their structure should be obvious to the reader.
Notation
This section contains a detailed description of the notation for the concept. Usually, the notation section has a form that parallels the preceding semantics section, which it references, and it often has the same divisions. The notation section usually includes one or more diagrams to illustrate the concept. The actual notation is printed in black ink. To help the reader understand the notation, many diagrams contain annotations in blue ink. Any material in blue is commentary and is not part of the actual notation.
Example
This subsection contains examples of notation or illustrations of the use of the concept. Frequently, the examples also treat complicated or potentially confusing situations.
Discussion
This section describes subtle issues, clarifies tricky and frequently confused points, and contains other details that would otherwise digress from the more descriptive semantics section. A minority of articles have a discussion section.
This section also explains certain design decisions that were made in the development of the UML, particularly those that may appear counterintuitive or that have provoked strong controversy. Only a fraction of articles have this section. Simple differences in taste are generally not covered.
Standard elements
This section lists standard constraints, tags, stereotypes, and other conventions that are predefined for the concept in the article. This section is fairly rare.
Syntax Conventions
Syntax expressions. Syntax expressions are given in a modified BNF format in a sans serif font. To avoid confusing literal values and syntax productions, literal values that appear in the target sentence are printed in black ink, and the names of syntax variables and special syntax operators are printed in blue ink.
Text printed in black ink appears in that form in the target string.
Punctuation marks (they are always printed in black) appear in the target string.
Any word printed in blue ink represents a variable that must be replaced by another string or another syntax production in the target string. Words may contain letters and hyphens. If a blue word is italicized or underlined, the actual replacement string must be italicized or underlined.
In code examples, comments are printed in blue ink to the right of the code text.
Subscripts and overbars are used as syntax operators (please refer to book for further information).
Literal strings. In running text, language keywords, names of model elements, and sample strings from models are shown in a sans serif font.
Diagrams. In diagrams, blue text and arrows are annotations, that is, explanations of the diagram notation that do not appear in an actual diagram. Any text and symbols in black ink are actual diagram notation.
CD
This book is accompanied by a CD containing the full text of the book in Adobe Reader (PDF) format. Using Adobe Reader, the viewer can easily search the book for a word or phrase. The CD version also contains a clickable table of contents, index, Adobe Reader thumbnails, and extensive hot links in the body of the articles. Simply click on one of the links to jump to the encyclopedia article for the word or phrase.
The CD also contains the full text of the OMG UML specifications, included by the permission of the Object Management Group.
We feel that this CD will be a useful on-line reference to UML for advanced users.
For More Information
Additional source files and up-to-date information on further work on UML and related topics can be found on the World Wide Web sites www.rational.com and www.omg.org
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