摘要
随着软件企业对过程能力要求的增加,成本估算作为提高过程管理的重要方法之一,也渐受企业的重视。有效的软件成本估算是软件产品合理控制和科学管理的前提,目前软件成本估算方法在国外已相对成熟,但在国内仍是项目管理中的一个薄弱环节。COCOMOII(Constructive Cost Model,构造性成本模型)是少数几种公开发表的成本估算模型中应用相对广泛和成熟的模型,并且可以针对不同组织进行裁剪和校准。因此如何从国内软件环境出发,找出对模型影响较大的因素,将模型进行改进使之适应国内软件环境具有极大的价值。本文的主要分析研究工作如下:
1.结合国内软件行业现状,分析了COCOMOII各成本因子的含义及取值,确立了改进目标和原则,对成本因子做了本地化改进,并给出了新的工作量估算公式。本地化改进减低了COCOMOII模型的复杂度和应用难度,节约了成本估算工作自身带来的工作量。
2.搜集了某企业的历史项目数据,采用线性回归法,借助最小二乘法数据处理软件,对新的工作量公式进行参数校准,经校准的工作量公式适用于本企业环境,从而提高了估算的准确度。
3.由于功能点转换为代码行后可作为本地化工作量估算公式的规模输入,于是本文改进了功能点规模估算方法。采用UML的用例建模技术和类图对功能点估算过程进行规范,并给出了映射规则。此改进为功能点估算过程提供指导的同时,在一定程度上缓解了国内软件企业文档不规范导致的功能分解随意性大的问题。
4.将模型应用于某企业的协同自动化办公系统中四个开发环境类似的模块,进行工作量估算,并将估算结果和采用原COCOMOII模型的工作量估算结果分别对比实际工作量,评估表明模型应用取得了良好的效果。
As software enterprises are increasingly in demand on process capability, software cost estimation which is one of the important methods of improving process management is gradually concerned by them. Effective software cost estimation is the premise of reasonable control and scientific management of software products. At present, software estimation methods are relative mature in foreign countries. But software estimation is a weak link in domestic project management. In those few published models, COCOMOII (Constructive Cost Model) is a relative widely used and mature model. So proceedding from domestic software environment, how to identify factors which have more effect on the model and how to impove the model to adapt to the domestic environment is very valuable. The main analysis and research works of this paper are as follows:
1. Combined with domestic software industry, analysised concept and value of every cost factor in COCOMOII, established the objectives and principles of improvement, improved cost factors localizedly, and provided a new formula for effort estimation. Localized improvement reduced the complexity and difficulty of application of the model. So it saved itself workload of cost estimation.
2. Collected historical project data in some enterprise, adopted linear regression method and used the data processing software of least square method to calibrate parameters in the new effort estimation formula. The formula whose parameters have been calibrated was more appropriate to the enterprise’s environment and helped to improve the accuracy of estimation.
3. Because function point could convert to lines of code as size input of the localization effort estimation formula, this paper improved function point method of size estimation. Used use case model modeling technology and class diagram of UML to standardize the process of function point estimation and provided mapping rules. This improvement provided guidance for the process of function point estimation. At the same time, it to some extent alleviated the problem of decomposing function randomly which is caused by non-standardized document in local enterprises.
4. Applicated model to four modules of Office Automation System in some enterprise to estimate effort. These modules are in similar development environment. Then compared the effort which was estimated by using new model with actual effort and compared the effort which was estimated by using original COCOMOII with actual effort respectively. The evaluation results showed that the model application effect is good.
引文
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