The Exterminators

The Exterminators - A small British firm shows that...

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36 IEEE Spectrum | September 2005 | NA www.spectrum.ieee.org Peter Amey was an aeronautical engineer serving in the United Kingdom’s Royal Air Force in the early 1980s when he found a serious flaw in an aircraft missile-control system being deployed at the time. It wasn’t a defect in any of the thousands of mechanical and elec- tronic parts that constituted the system’s hardware. The problem was in the system’s software. Amey found an erroneous piece of program code—a bug. Because of it, the unthink- able could happen: under rare circumstances, a missile could fire without anyone’s having commanded it to do so. Amey says his superiors, rather than commending his discovery, complained that it would delay the system’s deployment. Like most project managers, they didn’t like the idea of fixing errors at the end of the development process. After all, good design ought to keep errors out in the first place. Yet time and again, Amey knew, the software develop- ment process didn’t prevent bugs; it merely put off dealing with them until the end. Did it have to be that way? Or could developers avoid bugs in the first place? He would find the answer to be “yes” when, years later, he joined Praxis High Integrity Systems. Praxis, headquartered in Bath, 2 hours from London by car, was founded in 1983 by a group of software experts who firmly believed they could put together a sound methodol- ogy to ruthlessly exterminate bugs during all stages of a software project. At the time, the software world was in a malaise that it hasn’t fully shaken even today [see “Why Software Fails,” in this issue]. Software projects were getting larger and more complex, and as many as 70 percent of them, by some estimates, were running into trou- ble: going over budget, missing deadlines, or collapsing completely. Even projects consid- ered successful were sometimes delivering software without all the features that had been promised or with too many errors—errors that, as in the missile-firing system, were some- times extremely serious. The personal computer era, then just starting, only reinforced a development routine of “compile first, debug later.” A small British firm shows that software bugs aren't inevitable By Philip E. Ross
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ALL PHOTOS: PETER SEARLE CHECKING CODE: At Praxis, Peter Amey [ left ] and Roderick Chapman use mathematical logic to make sure their programs do not contain errors. www.spectrum.ieee.org September 2005 | IEEE Spectrum | NA 37
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38 IEEE Spectrum | September 2005 | NA www.spectrum.ieee.org Praxis armed itself not only with an arsenal of the latest soft- ware engineering methods but also with something a little more unusual in the field: mathematical logic. The company is one of the foremost software houses to use mathematically based techniques, known as formal methods, to develop software. Basically, formal methods require that programmers begin their
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This note was uploaded on 12/28/2010 for the course CSC CSC2120 taught by Professor Xiacai during the Spring '07 term at CUHK.

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The Exterminators - A small British firm shows that...

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