Real-Time Design Patterns

ISBN:0201699567
Pages:528
Date:2002-09-23
Publisher:Addison-Wesley Professional
Rating:4.0

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    Book Description
Goals Real-time and embedded systems (RTE systems) must execute in a much more constrained environment than "traditional" computer systems such as desktop and mainframe computers. RTE systems must be highly efficient, optimally utilizing their limited processor and memory resources, and yet must often outperform systems with significantly more compute power. In addition, many RTE systems have important safety-critical and high-reliability requirements because they are often used in systems such as avionics flight control, nuclear power plant control, life support and medical instrumentation. The creation of RTE systems to meet these functional and quality of service requirements requires highly experienced developers with decades of experience. Yet, over the years, these developers have encountered the same problems over and over--maybe not exactly the same problems but common threads. The very best developers abstract these problems and their solutions into generalized approaches that have proved consistently effective. These generalized approaches are called design patterns. They are often best applied at the level of the system or software architecture--the sum of design decisions that affect the fundamental organization of the system. Real-Time Design Patterns is an attempt to capture in one place a set of architectural design patterns that are useful in the development of RTE systems. Audience The book is oriented toward the practicing professional software developer and the computer science major in the junior or senior year. This book could also serve as an undergraduate- or graduate-level text, but the focus is on practical development rather than a theoretical dissertation. The book assumes a reasonable proficiency in at least one programming language and a basic understanding of the fundamental concepts of object orientation, the Unified Modeling Language (UML), and real-time systems. Organization Part I consists of three chapters. Chapter 1 provides a very brief review of the major concepts in the Unified Modeling Language. Chapter 2 introduces the fundamental concepts of architecture as they are defined in the Rapid Object-oriented Process for Embedded Systems (ROPES), including the primary division of architecture into logical (design-time) and physical (run-time) aspects, and the five important architectural views. In the third chapter, the book gets into a discussion of design patterns and their role in defining architecture. Because it is difficult to discuss architecture in a process-free environment, the ROPES process, and the key technologies it tries to optimize, are introduced to provide a background in which design patterns may be effectively discussed. Once process has been introduced, design patterns are next. Their various aspects are explained, and the fundamental organization of design patterns used in this book is provided. The chapter finishes with a discussion of how design patterns can be applied in the development of real systems. Part II contains the architectural design patterns that reify the ways that large-scale system components are organized and structured to optimize some set of general system criteria. The patterns in Part II are organized around the architectural concept they address. Chapter 4 is dedicated to high-level structural patterns--focused around what is called the Subsystem or Component architecture. Because concurrency and resource management is so crucial to real-time and embedded systems, Chapter 5 focuses on the common patterns of concurrency. Memory management is crucial for many systems in this domain, and it is the subject of Chapter 6. We see even more general resource management patterns in Chapter 7. Chapter 8 presents a number of common distribution architecture patterns that define how objects can be distributed across multiple address spaces and computers. Finally, Chapter 9 provides a number of patterns that deal with building safe and reliable architectures. Two appendixes appear at the end of the book. The first is simply a summary of the UML graphical notation, and the second is an index of the patterns by name. The CD-ROM provides a number of interesting and useful tools. It contains a full copy of the Rhapsody UML tool with instructions on how to get a temporary license from I-Logix. Other additional potentially useful tools for developers of real-time systems are also provided. The Papers chapter contains some papers on various topics as well as some useful OMG specifications. More Information Additional information on the UML, object-oriented technology, and the development of real-time systems can be found at www.ilogix.com. In addition, the current UML, MDA, and CORBA standards can be seen at www.omg.org. For more information on using the UML in real-time systems, Real-Time UML, 2nd Edition is also available from Addison-Wesley, as is the more comprehensive Doing Hard Time: Developing Real-Time Systems with UML, Objects, Frameworks and Patterns. Many other well-written and useful books on the UML and software engineering are similarly available. Acknowledgments A book like this is always a joint effort, not only of the direct contributors, such as the editorial staff of Addison-Wesley Professional (and I'd especially like to thank my editor, Paul Becker, for the sometimes less-than-gentle pushing to complete the book!) but of many others who in their own way have raised the bar for all of us. The core team members working on the UML--Cris Kobryn, Eran Gery, Jim Rumbaugh, Bran Selic, and many, many others are certainly among those who should be acknowledged in bringing forth a useful standard language for capturing and manipulating models of systems. Also, Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides deserve recognition for bringing the concept of design patterns into common use with their wonderful book Design Patterns: Elements of Reusable Object-Oriented Software. David Harel (inventor of statecharts, the semantic basis for all behavior in the UML) and Werner Damn continue to make significant contributions to the state of the art, especially with respect to formal verification of systems modeled with the UML. My two boys, Scott and Blake Douglass, continue to delight and amaze me--and keep me humble at the same time--and make all this effort worthwhile. 0201699567P08292002 /p>
Reviews From AMAZON.COM
Not just for real-time
Douglass' book does present a number of patterns useful in embedded, hardware-rich, and resource-constrained environments. More than that, though, he gives background material and discussion that work in OS and application environments, too.Chapters 4 to 9 lays out a number of patterns that work well in embedded environments. Patterns for any one aspect of the system (memory, safety/reliability, etc.) are grouped into chapters, allowing easy understanding of the relationships between patterns that differ only subtly. Ch.7, especially, covers a number of related patterns that address to dealock avoidance - good stuff, but a bit more comparison between patterns and discussion of how to select between them would have helped. The discussion on deadlock in general is good too, but a standard OS textbook might cover aspects of deadlock in more detail.Ch.6, on memory, will be a revelation to people who just use malloc() and free() without thinking. There are lots more ways of handling memory. His discussions of different patterns are good but there's always more to say. Memory pools, for example, may have many different meanings: different memory regions (cache vs. main memory) may have different performance features, or (as in DOS or Windows before about Win95) implications for the instruction sets required for memory access. Harvard and multi-bus architectures may use memory pools to reflect different memory accessibility rules. The "fixed-size buffer" pattern is another great one. I've seen it implemented in hardware, for on-chip buffers in network controllers, and in operating systems where objects of a specific data type are reused frequently. (This can overlap with the pool pattern, when there are different pools for buffers of different fixed sizes.)Ch.3 talks about patterns in general, and the discussion ranges widely. It includes a fairly good discussion of using multiple patterns in one application, but stops short of the tricky cases where one object participates in two different patterns.On the whole, this is a very useful book. It does presuppose some background in system (as opposed to software) design. That means it's not for the raw beginner, but it doesn't pretend to be. Some of the discussions of low-level system design suffer from shallowness, and some embedded topics are simply never discussed. Memory structures for block-erasable FLASH, for example, may resemble those used in writable CD-ROMs. Every book has bounds, though, and Douglass has done a good job within the bounds he chose.//wiredweird
Dedication
Software engineerGood at what you doAvoid Haiku like the plague