软件工程评估和管理英文讲义PSP6.ppt

1、CSEM01 - wk 6 - PSP,1,Personal Software Process,CSEM01 SE Evolution & ManagementAnne ComerHelen Edwards,CSEM01 - wk 6 - PSP,2,Personal Software ProcessObjectives,To describe the personal software process (PSP) To show where and how the PSP can be used to improve individual software engineering perfo

2、rmance,CSEM01 - wk 6 - PSP,3,The Software Problem,Poor software quality in delivered systems is expensive expensive service and enhancement potential for accident or loss of life Organizational progress with process improvement is limited because process improvement takes time, and is hard to sell,C

3、SEM01 - wk 6 - PSP,4,The PSP Solution,The PSP addresses these problems by providing convincing evidence of the benefits of process improvement exposing the engineers to the benefits of using effective processes in their work teaching the engineers effective process improvement methods providing the

4、historical data to better manage cost, schedule, and quality,CSEM01 - wk 6 - PSP,5,The PSP Paradigm,The PSP is based on process improvement principles. Software engineers establish personal process goals they define the methods to use they measure their work they analyze the results based on the res

5、ults, they adjust their methods to improve towards personal goals,CSEM01 - wk 6 - PSP,6,The PSP Strategy,Start with the s/w engineers current process Gradually introduce new methods Practice these methods on module-sized programs The engineers then see for themselves how these methods help them.,CSE

6、M01 - wk 6 - PSP,7,PSP Overview (i),The PSP is a process for individuals to use. It applies to most structured tasks. writing small programs or documents defining requirements or processes conducting reviews or tests, etc. It is extendible to team development of large-scale software systems.,CSEM01

7、- wk 6 - PSP,8,PSP Overview (ii),Individuals learn the PSP in seven steps. When learning PSP s/w engineers write 10 module-sized programs using the PSP steps. they gather and analyze data on their work based on these analyses they improve their working methods The PSP exercises provide the rapid fee

8、dback needed for effective learning.,CSEM01 - wk 6 - PSP,9,The PSP seven steps,PSP 0-1 Coding standard Process imprvmt proposal Size measurement,PSP 1-2 Task planning Schedule planning,PSP 2-3 Design templates,PSP 1 Size estimating report Test report,PSP 2 Code reviews Design reviews,PSP 3 Cyclic de

9、velopment,PSP 0 Current Process Basic measures,Team Software Process,CSEM01 - wk 6 - PSP,10,The PSP0 Process,With PSP0, engineers use their current design and development methods. They gather data on their work. the time spent by phase the defects found in compile and test They analyze and report th

10、ese data.,CSEM01 - wk 6 - PSP,11,The PSP0 Lessons,With PSP0, engineers learn to use a basic personal process. they gather data on their personal work and personal processes they learn how and why to measure the sizes of the products they produce,CSEM01 - wk 6 - PSP,12,The PSP1 Process,The PSP0 is au

11、gmented to include coding standards size estimating resource estimating schedule estimating test report earned value tracking process improvement proposal (PIP),CSEM01 - wk 6 - PSP,13,The PSP1 Lessons,With PSP1, engineers estimate the sizes and development times of the work they produce. they use th

12、eir historical data to improve their estimates they project the likely statistical ranges of their estimates and learn how to reduce these ranges,CSEM01 - wk 6 - PSP,14,PSP2 and PSP3 Lessons,With PSP2, engineers use their historical data to improve the quality of the program modules they produce. th

13、ey measure the efficiency of their defect removal methods they use various process quality measures, including yield, COQ (cost of quality), and A/FR (appraisal/failure ratio) With PSP3, engineers learn how to adjust their personal processes for different types of work.,CSEM01 - wk 6 - PSP,15,The Ba

14、sic PSP Elements,A process script A project plan summary form A time recording log A defect reporting log A defect type standard,CSEM01 - wk 6 - PSP,16,Process Script,Scripts guide the engineers through the process. purpose inputs required process phases exit criteria,CSEM01 - wk 6 - PSP,17,Project

15、Plan Summary,The project plan summary form holds project plan data actual project results size times defect data cumulative data on all PSP projects to date,CSEM01 - wk 6 - PSP,18,Time Recording Log,Time spent working on each PSP phase is recorded. start time stop time interrupt time phase comments,

16、CSEM01 - wk 6 - PSP,19,Defect Recording Log,Information on each defect found in reviews, compiling, and test is recorded. Number type phase injected phase removed find/fix time description,CSEM01 - wk 6 - PSP,20,The PSP Process Flow,Requirements,Process scripts,Project plan summary,Finished product,

17、Project and process data summary report,guide,Time and defect logs,CSEM01 - wk 6 - PSP,21,PSP Planning,In the PSP, engineers use their personal data to make plans. Planning consists of size estimating resource estimating schedule estimating In the PSP, lines of code (LOC) are used as the size measur

18、e Other measures could be used.,CSEM01 - wk 6 - PSP,22,Why Estimate Size?,To make better plans to better size the job to divide the job into separable elements To assist in tracking progress can judge when job scope changes can better measure the work Value for the PSP learn estimating methods build

19、 estimating skills,CSEM01 - wk 6 - PSP,23,Size Estimating Principles,Estimating is an uncertain and intuitive process. The estimating objectives are to make consistent estimates understand estimate variability balance under and over estimates Advantages of a defined estimating method are You have a

20、known practice you can improve. It provides a framework for gathering data. consistent method + historical data = consistent estimates,CSEM01 - wk 6 - PSP,24,The PSP Quality Strategy - 1,In the PSP, defects are the basic quality measure. Note - defects are not important to the user as long as they d

21、o not affect operations cause inconvenience cost time or money cause loss of confidence in the programs results,CSEM01 - wk 6 - PSP,25,The PSP Quality Strategy - 2,Low defect content is essential to a quality software process. Experienced software engineers typically inject around 100 defects per KL

22、OC. Defects are injected at the PSP level and this is where the engineers should remove them determine their causes learn to prevent them,CSEM01 - wk 6 - PSP,26,The PSP Quality Strategy - 3,If you want a quality product out of test, you must put a quality product into test. testing removes only a fr

23、action of the defects test is only meant to find defects - correction goes to developers (PC) To manage defects, they must be addressed where they are injected - by each software engineer.,CSEM01 - wk 6 - PSP,27,The PSP Quality Strategy - 4,Data show that it is much more efficient to find defects in

24、 reviews than in testing. in unit test, typically only about 2 to 4 defects are found per hour code reviews typically find about 10 defects per hour experienced reviewers can find 70% or more of the defects in a product unit test rarely exceeds a 50% yield PSP data show that reviews find 2 to 5 times as many defects per hou