考试系统可行性分析
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3,350
Computer graphics display facilities
4,950
Peripheral control function
2,100
Design analysis modules
8,400
Estimated lines of code
33,200
Thesoftware equationis a dynamic multivariable model that assumes a specific distribution of effort over the life of a software developmentproject.Themodel has been derived from productivity data collected for over 4,000 contemporary softwareprojects.Basedon thesedata,wederive an estimation model of the form
A set of use cases is developed by end users.
2、研究目前正在使用的系统
3、导出新系统的高层逻辑模型
4、重新定义问题
5、导出和评价供选择的方案
6、推荐一个方案并说明理由
7、Biblioteka Baidu荐行动方针
8、书写计划任务的可行性论证报告
9、提交审查
三、成本/效益分析
1、成本估算的方法
The availability of historical informationhas a strong influence on estimation risk.
2、成本估算的经验模型
It is very difficult to make avigorous,plausibleand job-risking defense of an estimate that is derived by not quantitativemethod,supportedby littledata,andcertified chiefly by the hunches of the managers.(Fred Brooks)
Typical values might be P=2,000 for development of real-time embeddedsoftware,P=10,000 for telecommunication and systemssoftware,andP=28,000 for business systems applications.
The mechanical CAD software will accept two- andthree-dimensional geometric data from adesigner.Allgeometicdata and other supporting information will be maintained in a CADdatabase.Designanalysis modules will be developed to produce the requiredoutput,whichwill be displayed on a variety ofdevices.Thesoftware will be designed to control and interact with peripheral devices that include amouse,scanner,laserprinter,andplotter.
二、方法步骤
1、确定系统规模和目标
Software scopedescribes the functions and features that are to be delivered to endusers;thedata that are input andoutput;the“content”that is presented to users as a consequence of using thesoftware;andtheperformance,constraints,interface,andreliability that bound the system.
Where
E =effort in person-months or person-years
t=project duration in months or years
B=special skillsfactor.Forsmallprograms(KLOC=5 to 15),B=0.16.For programs greater than 70 KLOC,B=0.39.
The degree of structural uncertaintyalso has an effect on estimationrisk.Inthiscontext,structurerefers to the degree to which requirements have beensolidified,theease with which functions can be compartmentalized and the hierarchical nature of the information that must be processed.
(1)
Gives heaviest credence tothe“most likely”estimate and follows a beta probability distribution.
An example of LOC-Based Estimation
We consider a software package to be developed for a computer-aided design application for mechanicalcomponents.Apreliminary statement of software scope can be developed:
A three-point or expected value can then becomputed.Theexpected value for the estimation variable S can be computed as a weighted average of theoptimistic,mostlikely,andpessimisticestimates.Forexample,
Function
Estimated LOC
User interface and control facilities
2,300
Two-dimensional geometric analysis
5,300
Three-dimensional geometric analysis
6,800
Database management
备课笔记2
一、任务
目的：用最小的代价在尽可能短的时间内确定问题是否能够解决。
实质：在尽可能短的时间内对软件项目进行一次简化的需求分析和设计工作。
1、经济可行性
2、技术可行性
3、运行可行性
4、法律可行性
5、开发方案可行性
可行性研究的最根本的任务是对以后的行动路线提出建议:如果所研究的问题没有可行的解，应建议停止其开发；如果值得解，应该推荐一个较好的解决方案，并且为工程制定一个初步的计划。
Project complexityhas a strong effort on the uncertainty inherent in planning.
Project sizeis another import factor that can affect the accuracy and efficacy of estimates.
Scope is defined using one of two techniques:
A narrative description of software scope is development after communication with all stakeholders(Astakeholderis anyone who has a stake in the successful outcome ofthe project-businessmanagers,endusers,softwareengineers,supportpeople,etc.).
A review of historical data indicates that the organizational average productivity for systems of this type is 620 LOC/person-month.Basedon a burdened labor rate of $8,000 permonth,thecost per LOC is approximately $13(=8000/620).Based on the LOC estimate and the historical productivitydata,thetotal estimated project cost is $431,000(=33200*13) and the estimated effort is 54(=33200/620) person-month.
Linesof code estimation
Regardless of the estimation variable that isused,youshould begin by estimating a range of values for each function or information domainvalue.Usinghistorical data orintuition,estimateanoptimistic,mostlikely,andpessimistic size value for each function or count for each information domain value.
Following the decomposition technique forLOC,anestimation tableisdeveloped.Arange of LOC estimates is developed for eachfunction.Forexample,therange of LOC estimates for the 3Dgeometricanalysis function is optimistic,4600LOC;mostlikely,6900LOC;andpessimistic,8600LOC.ApplyingEquation (1),the expected value for the 3D geometric analysis function is 6800LOC.Otherestimates are derived in a similarfunction.Bysumming vertically in the estimated LOCcolumn,anestimateof 33,200 LOC is established for the CAD system.
P=productivity parameter thatreflects:overallprocessmaturity and managementpractices,theextent to which good software engineering practices areused,thelevel of programming languagesused,thestate of the softwareenvironment,theskills and experience of the softwareteam,andthe complexity of the application.
Computer graphics display facilities
4,950
Peripheral control function
2,100
Design analysis modules
8,400
Estimated lines of code
33,200
Thesoftware equationis a dynamic multivariable model that assumes a specific distribution of effort over the life of a software developmentproject.Themodel has been derived from productivity data collected for over 4,000 contemporary softwareprojects.Basedon thesedata,wederive an estimation model of the form
A set of use cases is developed by end users.
2、研究目前正在使用的系统
3、导出新系统的高层逻辑模型
4、重新定义问题
5、导出和评价供选择的方案
6、推荐一个方案并说明理由
7、Biblioteka Baidu荐行动方针
8、书写计划任务的可行性论证报告
9、提交审查
三、成本/效益分析
1、成本估算的方法
The availability of historical informationhas a strong influence on estimation risk.
2、成本估算的经验模型
It is very difficult to make avigorous,plausibleand job-risking defense of an estimate that is derived by not quantitativemethod,supportedby littledata,andcertified chiefly by the hunches of the managers.(Fred Brooks)
Typical values might be P=2,000 for development of real-time embeddedsoftware,P=10,000 for telecommunication and systemssoftware,andP=28,000 for business systems applications.
The mechanical CAD software will accept two- andthree-dimensional geometric data from adesigner.Allgeometicdata and other supporting information will be maintained in a CADdatabase.Designanalysis modules will be developed to produce the requiredoutput,whichwill be displayed on a variety ofdevices.Thesoftware will be designed to control and interact with peripheral devices that include amouse,scanner,laserprinter,andplotter.
二、方法步骤
1、确定系统规模和目标
Software scopedescribes the functions and features that are to be delivered to endusers;thedata that are input andoutput;the“content”that is presented to users as a consequence of using thesoftware;andtheperformance,constraints,interface,andreliability that bound the system.
Where
E =effort in person-months or person-years
t=project duration in months or years
B=special skillsfactor.Forsmallprograms(KLOC=5 to 15),B=0.16.For programs greater than 70 KLOC,B=0.39.
The degree of structural uncertaintyalso has an effect on estimationrisk.Inthiscontext,structurerefers to the degree to which requirements have beensolidified,theease with which functions can be compartmentalized and the hierarchical nature of the information that must be processed.
(1)
Gives heaviest credence tothe“most likely”estimate and follows a beta probability distribution.
An example of LOC-Based Estimation
We consider a software package to be developed for a computer-aided design application for mechanicalcomponents.Apreliminary statement of software scope can be developed:
A three-point or expected value can then becomputed.Theexpected value for the estimation variable S can be computed as a weighted average of theoptimistic,mostlikely,andpessimisticestimates.Forexample,
Function
Estimated LOC
User interface and control facilities
2,300
Two-dimensional geometric analysis
5,300
Three-dimensional geometric analysis
6,800
Database management
备课笔记2
一、任务
目的：用最小的代价在尽可能短的时间内确定问题是否能够解决。
实质：在尽可能短的时间内对软件项目进行一次简化的需求分析和设计工作。
1、经济可行性
2、技术可行性
3、运行可行性
4、法律可行性
5、开发方案可行性
可行性研究的最根本的任务是对以后的行动路线提出建议:如果所研究的问题没有可行的解，应建议停止其开发；如果值得解，应该推荐一个较好的解决方案，并且为工程制定一个初步的计划。
Project complexityhas a strong effort on the uncertainty inherent in planning.
Project sizeis another import factor that can affect the accuracy and efficacy of estimates.
Scope is defined using one of two techniques:
A narrative description of software scope is development after communication with all stakeholders(Astakeholderis anyone who has a stake in the successful outcome ofthe project-businessmanagers,endusers,softwareengineers,supportpeople,etc.).
A review of historical data indicates that the organizational average productivity for systems of this type is 620 LOC/person-month.Basedon a burdened labor rate of $8,000 permonth,thecost per LOC is approximately $13(=8000/620).Based on the LOC estimate and the historical productivitydata,thetotal estimated project cost is $431,000(=33200*13) and the estimated effort is 54(=33200/620) person-month.
Linesof code estimation
Regardless of the estimation variable that isused,youshould begin by estimating a range of values for each function or information domainvalue.Usinghistorical data orintuition,estimateanoptimistic,mostlikely,andpessimistic size value for each function or count for each information domain value.
Following the decomposition technique forLOC,anestimation tableisdeveloped.Arange of LOC estimates is developed for eachfunction.Forexample,therange of LOC estimates for the 3Dgeometricanalysis function is optimistic,4600LOC;mostlikely,6900LOC;andpessimistic,8600LOC.ApplyingEquation (1),the expected value for the 3D geometric analysis function is 6800LOC.Otherestimates are derived in a similarfunction.Bysumming vertically in the estimated LOCcolumn,anestimateof 33,200 LOC is established for the CAD system.
P=productivity parameter thatreflects:overallprocessmaturity and managementpractices,theextent to which good software engineering practices areused,thelevel of programming languagesused,thestate of the softwareenvironment,theskills and experience of the softwareteam,andthe complexity of the application.