The value of software sizing

Context

One of the difficulties faced by software development Project Managers is estimating the cost and schedule for new projects. Previous industry surveys have concluded that software size and cost estimation is a significant technical area of concern. In order to estimate cost and schedule it is important to have a good understanding of the size of the software product to be developed. There are a number of techniques used to derive software size, with function points being amongst the most documented.

Objective

In this paper we explore the utility of function point software sizing techniques when applied to two levels of software requirements documentation in a commercial software development organisation. The goal of the research is to appraise the value (cost/benefit) which functional sizing techniques can bring to the project planning and management of software projects within a small-to-medium sized software development enterprise (SME).

Method

Functional counts were made at the bid and detailed functional specification stages for each of five commercial projects used in the research. Three variants of the NESMA method were used to determine these function counts. Through a structured interview session, feedback on the sizing results was obtained to evaluate its feasibility and potential future contribution to the company.

Results

The results of our research suggest there is value in performing size estimates at two appropriate stages in the software development lifecycle, with simplified methods providing the optimal return on effort expended.

Conclusion

The ‘Estimated NESMA’ is the most appropriate tool for use in size estimation for the company studied. The use of software sizing provides a valuable contribution which would augment, but not replace, the company’s existing cost estimation approach.     

功能点度量在软件开发中的应用

软件度量是管理、控制和改进软件过程的基础,然而软件规模的概念没有被很好地理解,也没有得到广泛应用。与传统的代码行度量相比较,采用功能点作为规模度量单位具有准确一致的优点。功能点是被证实的可信的软件规模度量方法,它在软件定价、变更管理、项目估算等方面可以起到积极的作用。功能点度量方法已成为软件度量的基础,也是客户与软件开发组织交流的基础。     

基于CMM第五级上的软件开发成本、质量和开发周期的回归分析

软件开发中,处于CMM第五级的开发团队拥有相对较高的过程成熟,而高度成熟的过程对开发成本、质量和开发周期具有重要的影响。使用线性回归模型对4个CMM第五级的团队所开发的37个项目进行数据采集和研究后,发现此时大部分被认为影响软件开发成本、质量和开发周期的因素的作用被削弱了,而其中最重要的因素是软件规模。     

PSAMS: a communication protocol specification assessment and measurement system

An obstacle to the uses of software metrics and size models, which we have developed for measuring the complexity and maintainability of a communication protocol specified in Estelle and for estimating the size of its specification and implementation, is the time‐consuming effort in collecting the metrics. To address this problem, a software system called PSAMS (protocol specification assessment and measurement system) for automatically calculating the metrics and sizes of specification and implementation has been developed. This paper describes the design of PSAMS, which provides five functionalities for a communication protocol Estelle specification: exploring its specification, measuring its complexity, assessing its maintainability, estimating its specification size and estimating its implementation size. To demonstrate the usefulness of PSAMS, we have applied it to measure the complexity and maintainability of 10 communication protocol Estelle specifications; the measurement results and decision support information provided by each functionality are presented in this paper. With PSAMS, communication protocol designers and developers are able to assess the complexity of a communication protocol early in the specification stage and have information which helps them manage a communication software project better. Copyright © 2002 John Wiley & Sons, Ltd.     

Comparing the top-down and bottom-up approaches of function point analysis: a case study

Function point analysis is a widely cited method for estimating software project size, which is an important activity of project management. At the beginning stage of planning, the top-down approach can be applied. Having obtained more systems specifications at later stages, the bottom-up approach might also be used to improve the accuracy of the estimation. However, the bottom-up approach is not a conventional way of function point analysis. There was no empirical evidence showing the difference between the fully informed top-down approach and the bottom-up approach. Through the implementation of a function point analysis system in an in-house software development department, this paper compares the results of the two approaches. This comparison study shows that the bottom-up approach does not contribute a significant added value to a fully-informed top-down approach. Therefore, the fully-informed top down approach has been chosen as a method for building a software metric database in the organization. More important, the observations and experience gained from this project may help in-house development organizations to establish their own function point analysis systems.     

采用功能点分析法度量软件规模应用研究

对软件规模进行估算和度量已经成为软件规范化开发的基础要求,针对现有软件规模估算中功能点分析法的计算规则及其不足,提出了一种可行的功能点分析法实施准则,并运用线性回归数学模型对开发项目实例的数据进行了演算和分析,评价结果表明线性回归数学模型的可靠性和准确性.     

污水处理厂自控系统的形式、结构和功能

本文介绍了国内污水处理厂目前采用的几种自控系统的形式和特点,并就应用较为广泛的IPC＋PLC型自控系统在污水处理厂应用中的网络结构和功能做了简要介绍。     

Software measurement: Problems and practice

Software measurement is a key element in the evolving software engineering discipline. This paper seeks to identify some of the principal problems surrounding the measurement process and the metrics themselves. Metrics are shown in various modeling contexts. Measures of static software complexity are explored together with measures of dynamic program complexity. These data are then used to identify regions of software that are fault prone. This information is then exploited to develop a model of dynamic program complexity for the identification of failure prone software. Empirical experiences with the practice of measurement from an ongoing research project on the Space Shuttle Primary Avionics Software System are employed to augment the discussion.     

Effort, co-operation and co-ordination in an open source software project: GNOME

Abstract This paper presents results from research into open source projects from a software engineering perspective. The research methodology employed relies on public data retrieved from the CVS repository of the GNOME project and relevant discussion groups. This methodology is described, and results concerning the special characteristics of open source software development are given. These data are used for a first approach to estimating the total effort to be expended.     

Convertibility of Function Points into COSMIC Function Points: A study using Piecewise Linear Regression

Background

COSMIC Function Points and traditional Function Points (i.e., IFPUG Function Points and more recent variation of Function Points, such as NESMA and FISMA) are probably the best known and most widely used Functional Size Measurement methods. The relationship between the two kinds of Function Points still needs to be investigated. If traditional Function Points could be accurately converted into COSMIC Function Points and vice versa, then, by measuring one kind of Function Points, one would be able to obtain the other kind of Function Points, and one might measure one or the other kind interchangeably. Several studies have been performed to evaluate whether a correlation or a conversion function between the two measures exists. Specifically, it has been suggested that the relationship between traditional Function Points and COSMIC Function Points may not be linear, i.e., the value of COSMIC Function Points seems to increase more than proportionally to an increase of traditional Function Points.

Objective

This paper aims at verifying this hypothesis using available datasets that collect both FP and CFP size measures.

Method

Rigorous statistical analysis techniques are used, specifically Piecewise Linear Regression, whose applicability conditions are systematically checked. The Piecewise Linear Regression curve is a series of interconnected segments. In this paper, we focused on Piecewise Linear Regression curves composed of two segments. We also used Linear and Parabolic Regressions, to check if and to what extent Piecewise Linear Regression may provide an advantage over other regression techniques. We used two categories of regression techniques: Ordinary Least Squares regression is based on the usual minimization of the sum of squares of the residuals, or, equivalently, on the minimization of the average squared residual; Least Median of Squares regression is a robust regression technique that is based on the minimization of the median squared residual. Using a robust regression technique helps filter out the excessive influence of outliers.

Results

It appears that the analysis of the relationship between traditional Function Points and COSMIC Function Points based on the aforementioned data analysis techniques yields valid significant models. However, different results for the various available datasets are achieved. In practice, we obtained statistically valid linear, piecewise linear, and non-linear conversion formulas for several datasets. In general, none of these is better than the others in a statistically significant manner.

Conclusions

Practitioners interested in the conversion of FP measures into CFP (or vice versa) cannot just pick a conversion model and be sure that it will yield the best results. All the regression models we tested provide good results with some datasets. In practice, all the models described in the paper - in particular, both linear and non-linear ones - should be evaluated in order to identify the ones that are best suited for the specific dataset at hand.     

Object-Oriented Function Points: An Empirical Validation

We present an empirical validation of object-oriented size estimation models. In previous work we proposed object oriented function points (OOFP), an adaptation of the function points approach to object-oriented systems. In a small pilot study, we used the OOFP method to estimate lines of code (LOC). In this paper we extend the empirical validation of OOFP substantially, using a larger data set and comparing OOFP with alternative predictors of LOC. The aim of the paper is to gain an understanding of which factors contribute to accurate size prediction for OO software, and to position OOFP within that knowledge. A cross validation approach was adopted to build and evaluate linear models where the independent variable was either a traditional OO entity (classes, methods, association, inheritance, or a combination of them) or an OOFP-related measure. Using the full OOFP process, the best size predictor achieved a normalized mean squared error of 38%. By removing function point weighting tables from the OOFP process, and carefully analyzing collected data points and developer practices, we identified several factors that influence size estimation. Our empirical evidence demonstrates that by controlling these factors size estimates could be substantially improved, decreasing the normalized mean squared error to 15%—in relative terms, a 56% reduction.     

软件开发成本估算技术综述

本文分析了软件开发成本估算精确性的影响因素,并对现有的软件开发成本估算技术进行分类和比较,探讨了软件开发成本估算技术的应用策略及其发展方向。     

An empirical study of the effect of complexity, platform, and program type on software development effort of business applications

Several popular cost estimation models like COCOMO and function points use adjustment variables, such as software complexity and platform, to modify original estimates and arrive at final estimates. Using data on 666 programs from 15 software projects, this study empirically tests a research model that studies the influence of three adjustment variables—software complexity, computer platform, and program type (batch or online programs) on software effort. The results confirm that all the three adjustment variables have a significant effect on effort. Further, multiple comparison of means also points to two other results for the data examined. Batch programs involve significantly higher software effort than online programs. Programs rated as complex have significantly higher effort than programs rated as average.     

An integrated approach to topology,sizing, and shape optimization

Topology optimization has become very popular in industrial applications, and most FEM codes have implemented certain capabilities of topology optimization. However, most codes do not allow simultaneous treatment of sizing and shape optimization during the topology optimization phase. This poses a limitation on the design space and therefore prevents finding possible better designs since the interaction of sizing and shape variables with topology modification is excluded. In this paper, an integrated approach is developed to provide the user with the freedom of combining sizing, shape, and topology optimization in a single process.     

The Function Model of Monitoring and Diagnosis System Based on Multiagent

智能监测与诊断是现代故障诊断的发展方向。采用组件化思想构建了基于多Agent的监测与诊断系统功能模型,并对该模型中的每一功能Agent的内部结构作了详细的描述。该模型具有统一的信息接口,根据实际监测对象的不同,可以选用不同的功能组件构建系统。该模型对智能监测与诊断系统的实现具有一定的指导意义,有利于建立集成化、智能化、自动化和网络化的诊断系统。     

Function point measurement from Web application source code based on screen transitions and database accesses

A function point (FP) is a unit of measurement that expresses the degree of functionality that an information system provides to a user. Many software organizations use FPs to estimate the effort required for software development. However, it is essential that the definition of 1 FP be based on the software development experience of the organization. In the present study, we propose a method by which to automatically extract data and transaction functions from Web applications under several conditions using static analysis. The proposed method is based on the International Function Point Users Group (IFPUG) method and has been developed as an FP measurement tool. We applied the proposed method to several Web applications and examined the difference between FP counts obtained by the tool and those obtained by a certified FP specialist (CFPS). The results reveal that the numbers of data and transaction functions extracted by the tool is approximately the same as the numbers of data and transaction functions extracted by the specialist.     

考虑测试工作量和故障检测率的软件可靠性模型

针对软件可靠性模型中对故障检测率行为描述的不足,考虑软件固有的故障检测率是一个随时间增加的减函数,以及测试人员的学习能力是一个随时间增加呈S型的增函数,两者共同决定了故障检测率是一个随时间增加的先增后减的函数,于是提出改进的软件可靠性模型。在改进模型的基础上,考虑测试工作量对可靠性的影响,软件可靠性模型得到了进一步的改善。利用公开发表的失效数据集对改进的模型进行比较和验证,实验数据证明改进的模型具有很好的效果。     

The influence of the search complexity and the familiarity with the website on the subjective appraisal of aesthetics,mental effort and usability

The user experience is defined as ‘a person's perceptions and responses that result from the use and/or anticipated use of a product, system or service’ (ISO FDIS 9241-210, 2009 ISO FDIS 9241-210, 2009. Ergonomics of human system interaction Ergonomics of human system interaction – Part 210: human-centered design for interactive systems (formerly known as 13407). Switzerland: International Organization for Standardization. [Google Scholar]) [Ergonomics of human system interaction Ergonomics of human system interaction – Part 210: human-centered design for interactive systems (formerly known as 13407). Switzerland: International Organization for Standardization]. Accordingly, some authors have argued that an interactive system has to be evaluated not only with regard to its usability and utility levels, but also with regard to emotional, attractiveness, and aesthetic levels. These last aspects play a substantial role on the general assessment of such systems and on the satisfaction of users. Some studies focused on the immediate aesthetic subjective perception of systems, on their subjective usability and preference perceptions. However, few studies, at least to our knowledge, have been focused on the reverse, that is, on the effect of difficulties experienced by individuals in using systems on the aesthetic appraisal. The present study aimed at determining the role of familiarity level with the website and the search complexity on the search performance and post-experiment appraisals of aesthetics, usability, and mental effort. The main results revealed that the search complexity affected negatively search performance, whereas the familiarity level affected only the re-reading of the search questions. The post-use assessments of aesthetics, mental effort, and usability satisfaction were affected by search performance. In addition, these variables were correlated except the expressive aesthetics, which seemed to be independent from the search performance and other subjective appraisals. Then, we discuss these findings in line with prior studies and present future ways of research.     

面向点云模型的交互式位姿调整系统

STL模型文件只有点云数据,其建模坐标系的位置姿态在建模时便已确定。针对在建模后修改其建模坐标系位姿困难的问题,结合Qt与OpenGL开发平台,开发出一套面向STL点云模型的交互式位姿调整系统。该系统以STL模型文件的点云数据作为基础图元操作对象,通过交互式的手段构造出新的辅助性图元,利用这些新的辅助性图元完成调整STL模型建模坐标系的位姿调整工作,并重新导出调整后的STL 模型文件。简单介绍系统中各组成模块后,对其中的一些关键性技术进行详细的论述,最后通过两个典型的调姿例子验证了系统的可靠性。