软件工程实践者的研究方法chapter11.ppt

These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill,2009).Slides copyright 2009 by Roger Pressman.1Chapter 11nQuality ConceptsSlide Set to accompanySoftware Engineering:A Practitioners Approach,7/e by Roger S.PressmanSlides copyright 1996,2001,2005,2009 by Roger S.PressmanFor non-profit educational use onlyMay be reproduced ONLY for student use at the university level when used in conjunction with Software Engineering:A Practitioners Approach,7/e.Any other reproduction or use is prohibited without the express written permission of the author.All copyright information MUST appear if these slides are posted on a website for student use.These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill,2009).Slides copyright 2009 by Roger Pressman.2Software QualitynIn 2005,ComputerWorld Hil05 lamented that n“bad software plagues nearly every organization that uses computers,causing lost work hours during computer downtime,lost or corrupted data,missed sales opportunities,high IT support and maintenance costs,and low customer satisfaction.nA year later,InfoWorld Fos06 wrote about the n“the sorry state of software quality”reporting that the quality problem had not gotten any better.nToday,software quality remains an issue,but who is to blame?nCustomers blame developers,arguing that sloppy practices lead to low-quality software.nDevelopers blame customers(and other stakeholders),arguing that irrational delivery dates and a continuing stream of changes force them to deliver software before it has been fully validated.These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill,2009).Slides copyright 2009 by Roger Pressman.3QualitynThe American Heritage Dictionary defines quality as n“a characteristic or attribute of something.”nFor software,two kinds of quality may be encountered:nQuality of design encompasses requirements,specifications,and the design of the system.nQuality of conformance is an issue focused primarily on implementation.nUser satisfaction=compliant product+good quality+delivery within budget and scheduleThese slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill,2009).Slides copyright 2009 by Roger Pressman.4QualityA Philosophical ViewnRobert Persig Per74 commented on the thing we call quality:nQuality.you know what it is,yet you dont know what it is.But thats self-contradictory.But some things are better than others,that is,they have more quality.But when you try to say what the quality is,apart from the things that have it,it all goes poof!Theres nothing to talk about.But if you cant say what Quality is,how do you know what it is,or how do you know that it even exists?If no one knows what it is,then for all practical purposes it doesnt exist at all.But for all practical purposes it really does exist.What else are the grades based on?Why else would people pay fortunes for some things and throw others in the trash pile?Obviously some things are better than others.but whats the betterness?.So round and round you go,spinning mental wheels and nowhere finding anyplace to get traction.What the hell is Quality?What is it?These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill,2009).Slides copyright 2009 by Roger Pressman.5QualityA Pragmatic ViewnThe transcendental view argues(like Persig)that quality is something that you immediately recognize,but cannot explicitly define.nThe user view sees quality in terms of an end-users specific goals.If a product meets those goals,it exhibits quality.nThe manufacturers view defines quality in terms of the original specification of the product.If the product conforms to the spec,it exhibits quality.nThe product view suggests that quality can be tied to inherent characteristics(e.g.,functions and features)of a product.nFinally,the value-based view measures quality based on how much a customer is willing to pay for a product.In reality,quality encompasses all of these views and more.These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill,2009).Slides copyright 2009 by Roger Pressman.6Software QualitynSoftware quality can be defined as:nAn effective software process applied in a manner that creates a useful product that provides measurable value for those who produce it and those who use it.n This definition has been adapted from Bes04 and replaces a more manufacturing-oriented view presented in earlier editions of this book.These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill,2009).Slides copyright 2009 by Roger Pressman.7Effective Software ProcessnAn effective software process establishes the infrastructure that supports any effort at building a high quality software product.nThe management aspects of process create the checks and balances that help avoid project chaosa