Research And Application Of Value Adjustment Factor Based On IFPUG Function Point Analysis Method

To have an overall and thorough understanding of the project in the early stage, the software size measurement is one of the key technologies in the software project field. Currently, there are a great deal of measurement methods, however, the most widely used method is FPA (Functional Point Analysis) of IFPUG (International Function Point Users Group), which is the focus of study by this paper.Even though it has a wide application, the FPA has following disadvantages in the process of being used: 1.When calculating the VAF (Value Adjustment Factor) of software project by FPA, it has been found out that the valued rule default of DI (Degree of Influence) of 14 GSC (General System Characteristics) is not reasonable enough, which leads to 7% increase in the software size after the adjustment under "Average Influence" of DI. 2. The various functional models of the software project will show different character properties, therefore, AFP (Adjusted Function Point) of various function models should be calculated in accordance with the VAF which determined by those character properties.To make an improvement to the disadvantages mentioned above, this paper aims to make an analysis and tries to overcome them by improving FPA method: 1.Readjusting the assignment rules of GSC's DI and the formula for calculating the VAF, Consequently, when the degree of influence of the GSC is moderate, the DI value is 0; and the improved formula for the calculation of VAF made VAF being 1 when the degree of influence of all GSC are moderate; At last inducting weight on the DI value, the greater GSC influencing the target system, the bigger DI's weight value. The same is true if it is vice versa. Therefore the result of VAF will be more reasonable. 2. Proposing a new calculating process of AFP, dividing the estimated system into different functional models, with each one has a separate calculated VAF, calculate the product of VAF and UFP (Unadjusted Function Point) and the result will be AFP of different functional models. Then give the result of the total sum of the AFP of different functional models. The result of the total sum will be AFP of estimated system. This method will improve the estimated results of software size and surely have a more reasonable ending.In conclusion, the paper also makes a comparison between the FPA method and the improved method the paper discusses. The results showed that the improved method the paper is discussing based on the FPA method in estimating the software size is more closely functional on the factual development of the situation.