摘要
软件度量和估算能够有效的监控软件进度。在常用软件度量方法中，对规模的度量和估算是所有度量活动的基础，其结果可作为其它度量的一个主要输入，因此在软件度量活动中具有重要地位。软件规模度量和估算的根本目的是通过量化的分析与总结，提高软件项目的生产率，提高产品质量，降低成本和产品研发周期，尽可能的减少因错误估算给企业带来的损失。
在众多的软件规模度量的技术中，国际功能点用户组IFPUG(International Function Point Users Group)的FPA(Function Points Analysis)方法得到了最广泛的应用，本文在规模度量一般方法的基础上，重点对FPA方法进行了详细探讨。
本文分析了FPA方法的优缺点。功能点最大程度地突破了传统评估方法的局限，能够不依赖于外部条件，客观、公正、独立地评估系统的规模。但是，传统的功能规模度量为手工操作，不仅抽取数据及度量过程非常繁琐、容易发生差错，而且度量人员不同，工作方法亦不同，带有很强的主观性，结论很难具有可重复性，所以亟需实现自动化地度量。
UML(Unified Modeling Language)是一种总结了以往建模技术的经验并吸收当今优秀成果的标准建模方法，它的提出和普遍应用，为客观、可比较、自动化地度量功能点提供了可能性。
为了解决FPA方法不能自动化度量的缺点，本文引入UML标准建模方法来对FPA进行改进。通过对UML顺序图和类图的分析，定义了相应的度量元映射规则，提取度量信息，从而自动的从顺序图中抽取出事务功能点，从类图中抽取出数据功能点，并最终得到FPA的功能点个数。本文描述了该规则的转换算法，实现了一种基于UML的自动化功能点度量工具—UBFPT(UML Based Function Point Tool)。它具有友好的用户界面，使用方便，以Rational Rose定义的MDL文件为基本输入，并以表格的形式将计算结果返回给用户。最后通过实验证明，该工具能够比较准确的对系统功能点进行自动化度量。
The scale measurement and estimation are the foundation of software measurements,the results are major inputs for other measurements. Thus it is of importance in softwaremeasurement activity. The basic goal of scale measurement is to increase project'sproductivity, enhance quality, and reduce cost and researching period through quantitativeanalysis.
Among the scale measurement, IFPUG' (International Function Point Users Group)FPA (Function Points Analysis) is one of the most widely used methods; this paperfocuses on the detailed investigation of FPA.
Although function point is widely accepted and used, this method is manual, and theprocess of extracting and measuring data is very complex and easy to get mistakes.Different person uses different methods. This brings a strong subjectivity, and the result isdifficult to repeat. Thus it is expected to make this method automatically.
UML is a standard modeling language that summarizes the experience of pastmodeling technologies and assimilate current modeling excellent achievement. Thefunction point measurement can be done impersonally, objectively based on UMLmodels.
This paper introduces UML models into FPA in order to overcome the shortcomingsof FPA. The proposed approach uses the Sequence diagrams and class diagrams in UMLmodels. The paper describes FPA measurement mapping rules for Sequence diagrams andclass diagrams respectively. Measurement data extracted from Sequence diagrams arecalled transaction function points, those extracted from class diagrams are data functionpoints. From the both kinds of function points the total function points of a softwaresystem can be calculated. Algorithms which automatically transform the mapping rulesare also presented in the paper. Then a fimction point tool UBFPT (UML Based FunctionPoint Tool) is described. Finally, experiments are performed and shown that the methodand the tool can calculate system function points relative exactly.
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