Embedded Systems September 2000 Vol13_10

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JEFFREY TAYLOR Book Review: Doing Hard Time: Developing Real-Time Systems with UML, Objects, Frameworks, and Patterns by Bruce Powel Douglass mce Powel Douglass is a writer with an attitude. He is passionate and enthusiastic about real- time systems, safety and reliability, and direct execution of models. In Texas, to where I've just moved, attitude, passion, and enthusiasm are a part of the cultu re. Your mileage, as they say, may vary. msafe enough' looks different at 35,000 feet." The Boeing 777 has been described as a million lines of Ada flying in tight formation. It is a completely fly-by-wire system. No mechanical or hydraulic linkages sit between the pilot's controls and the control surfaces, just those lines of code. I've got an attitude, too, about the safety and reliabili ty of that code. In spite of the subtitl e, this book is relevan t to most soft- ware developers, not just real-time developers. Even though embedded systems are the most common kind of computer (there are more microwaves and VCRs than mainframes and PCs), true real-time systems are not common. Mostly people want real fast. And they wan t it real soon. Most of the p roblems addressed by this book are present in modern applications with GUis and Web or ne twork connectivi ty. Only the sections on schedulability apply exclusively to real- time systems. Altl1ough not included in the subtitle, pmcess is a big part of this book. Douglass pushes process but is also realis- tic about it (for example, architectural design can be skipped in small systems) . He lists the relevant IEEE stan- dards and says that most can be fulfi lled in a couple of pages. The purpose of process is to ask the right questions at the appropriate time, not fi ll a cabinet with "objective evi- dence" for auditors. Douglass's flavor of process is Rapid Object-oriented Process for Embedded Systems (ROPES). Ifyou've been fol- lowing OOA/ D development, there is nothing terribly radi- cal here. He puts a heavier emphasis on safety than most treatments. He is an advocate of code generation from UML, so his usage of UML is more complete than most. UML statechar ts, a kind of state diagrams derived from Hare! statecharts, get a lot of coverage. This is because they fully specifY the behavior, not just the interfaces. UML state- char ts can be execu ted and debugged at the UML level. Class diagrams, on the other hand, can be used to generate header fil es but not executable code. Some of his ideas have me jumping up and down, saying, "yes, that is what I've been trying to do." Others do not. For Embedded Systems Programming SEPTEMBER 2ooo 199

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