《软件工程-实践者的研究方法》cha.ppt

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1、1,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,Chapter 21,Project Scheduling,Slide Set to accompanySoftware Engineering:A Practitioners Approach,7/e by Roger S.PressmanSlides copyright 1996,2001,20

2、05,2009 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 autho

3、r.All copyright information MUST appear if these slides are posted on a website for student use.,2,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,Why Are Projects Late?,an unrealistic deadline establ

4、ished by someone outside the software development groupchanging customer requirements that are not reflected in schedule changes;an honest underestimate of the amount of effort and/or the number of resources that will be required to do the job;predictable and/or unpredictable risks that were not con

5、sidered when the project commenced;technical difficulties that could not have been foreseen in advance;human difficulties that could not have been foreseen in advance;miscommunication among project staff that results in delays;a failure by project management to recognize that the project is falling

6、behind schedule and a lack of action to correct the problem,3,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,Scheduling Principles,compartmentalizationdefine distinct tasksinterdependencyindicate tas

7、k interrelationship effort validationbe sure resources are availabledefined responsibilitiespeople must be assigneddefined outcomeseach task must have an outputdefined milestonesreview for quality,4,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill

8、2009).Slides copyright 2009 by Roger Pressman.,Effort and Delivery Time,5,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,Effort Allocation,“front end”activities customer communication analysis design

9、 review and modificationconstruction activities coding or code generationtesting and installation unit,integration white-box,black box regression,6,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,Defi

10、ning Task Sets,determine type of projectassess the degree of rigor requiredidentify adaptation criteriaselect appropriate software engineering tasks,7,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,T

11、ask Set Refinement,1.1 Concept scoping determines the overall scope of the project.,Task definition:Task 1.1 Concept Scoping 1.1.1Identify need,benefits and potential customers;1.1.2Define desired output/control and input events that drive the application;1.1.2.1FTR:Review written description of nee

12、d FTR indicates that a formal technical review(Chapter 26)is to be conducted.1.1.2.2Derive a list of customer visible outputs/inputs1.1.2.3FTR:Review outputs/inputs with customer and revise as required;1.1.3Define the functionality/behavior for each major function;1.1.3.1FTR:Review output and input

13、data objects derived in task 1.1.2;1.1.3.2Derive a model of functions/behaviors;1.1.3.3FTR:Review functions/behaviors with customer and revise as required;1.1.4Isolate those elements of the technology to be implemented in software;1.1.5Research availability of existing software;1.1.6Define technical

14、 feasibility;1.1.7Make quick estimate of size;1.1.8Create a Scope Definition;endTask definition:Task 1.1,is refined to,8,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,Define a Task Network,9,These s

15、lides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,Timeline Charts,10,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pr

16、essman.,Use Automated Tools toDerive a Timeline Chart,11,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,Schedule Tracking,conduct periodic project status meetings in which each team member reports pr

17、ogress and problems.evaluate the results of all reviews conducted throughout the software engineering process.determine whether formal project milestones(the diamonds shown in Figure 27.3)have been accomplished by the scheduled pare actual start-date to planned start-date for each project task liste

18、d in the resource table(Figure 27.4).meet informally with practitioners to obtain their subjective assessment of progress to date and problems on the horizon.use earned value analysis(Section 27.6)to assess progress quantitatively.,12,These slides are designed to accompany Software Engineering:A Pra

19、ctitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,Progress on an OO Project-I,Technical milestone:OO analysis completed All classes and the class hierarchy have been defined and reviewed.Class attributes and operations associated with a class have been defined and re

20、viewed.Class relationships(Chapter 8)have been established and reviewed.A behavioral model(Chapter 8)has been created and reviewed.Reusable classes have been noted.Technical milestone:OO design completedThe set of subsystems(Chapter 9)has been defined and reviewed.Classes are allocated to subsystems

21、 and reviewed.Task allocation has been established and reviewed.Responsibilities and collaborations(Chapter 9)have been identified.Attributes and operations have been designed and reviewed.The communication model has been created and reviewed.,13,These slides are designed to accompany Software Engin

22、eering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,Progress on an OO Project-II,Technical milestone:OO programming completedEach new class has been implemented in code from the design model.Extracted classes(from a reuse library)have been implemented.Proto

23、type or increment has been built.Technical milestone:OO testingThe correctness and completeness of OO analysis and design models has been reviewed.A class-responsibility-collaboration network(Chapter 6)has been developed and reviewed.Test cases are designed and class-level tests(Chapter 19)have been

24、 conducted for each class.Test cases are designed and cluster testing(Chapter 19)is completed and the classes are integrated.System level tests have been completed.,14,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by

25、Roger Pressman.,Earned Value Analysis(EVA),Earned valueis a measure of progressenables us to assess the“percent of completeness”of a project using quantitative analysis rather than rely on a gut feeling“provides accurate and reliable readings of performance from as early as 15 percent into the proje

26、ct.”Fle98,15,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,Computing Earned Value-I,The budgeted cost of work scheduled(BCWS)is determined for each work task represented in the schedule.BCWSi is the

27、 effort planned for work task i.To determine progress at a given point along the project schedule,the value of BCWS is the sum of the BCWSi values for all work tasks that should have been completed by that point in time on the project schedule.The BCWS values for all work tasks are summed to derive

28、the budget at completion,BAC.Hence,BAC=(BCWSk)for all tasks k,16,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,Computing Earned Value-II,Next,the value for budgeted cost of work performed(BCWP)is co

29、mputed.The value for BCWP is the sum of the BCWS values for all work tasks that have actually been completed by a point in time on the project schedule.“the distinction between the BCWS and the BCWP is that the former represents the budget of the activities that were planned to be completed and the

30、latter represents the budget of the activities that actually were completed.”Wil99 Given values for BCWS,BAC,and BCWP,important progress indicators can be computed:Schedule performance index,SPI=BCWP/BCWSSchedule variance,SV=BCWP BCWSSPI is an indication of the efficiency with which the project is u

31、tilizing scheduled resources.,17,These slides are designed to accompany Software Engineering:A Practitioners Approach,7/e(McGraw-Hill 2009).Slides copyright 2009 by Roger Pressman.,Computing Earned Value-III,Percent scheduled for completion=BCWS/BACprovides an indication of the percentage of work th

32、at should have been completed by time t.Percent complete=BCWP/BACprovides a quantitative indication of the percent of completeness of the project at a given point in time,t.Actual cost of work performed,ACWP,is the sum of the effort actually expended on work tasks that have been completed by a point in time on the project schedule.It is then possible to computeCost performance index,CPI=BCWP/ACWPCost variance,CV=BCWP ACWP,