Research Of Use Case-Driven Full Function Points Sizing

Software size estimation is the basis of the software project planning; the risk of estimation is the primary risk during the project. Hence the software size estimation is one of the most important subjects in the software engineering area. At the present time, there are many standards of Function Point that is representative of IFPUG FPA, MK II and COSMIC-FFP since 1970s'.COSMIC-Full Function Points is the new generation functional sizing method which divides software system's processes into data movement and data manipulation. Data movement can be divided into four subtypes: entry, exit, read and write. The size of software can be measured by calculating the number of the four types of data movement.At present, UML is the most popular software modeling language. In the past, other people had done some researches on COSMIC-FFP based on UML. But the methods they defined either have not detailed calculating rules or can only be used at the end of requirements developing stage. In order to give software size estimation accurately at early stage of project lifecycle, the author propose a new estimation model, called UCD-FFP, according to the practical experiences in eight companies after doing a lot of research on the advantages and shortcomings of COSMIC-FFP. The advantages of UCD-FFP are as follows:1. UCD-FFP is based on the Use Case model and can be used after validating user requirements. It is independent on the Class diagram, Sequence diagram and Activity diagram. This method can be used to do software size estimation at the early stage.2. UCD-FFP divides the calculating rules and calculating principles of COSMIC-FFP into three types of rules: Sufficiency rule, necessary rule and heuristic rule. UCD-FFP also defines the strategy to describe the usage of the three rules, which can improve the efficiency of estimation.3. UCD-FFP defines and enumerates the above three types of rules based on UseCase Model which can reduce the dependency of relevant stakeholders'experiences who will take part in software size estimation so that theaccuracy of estimation can be improved.This paper discusses the history of function point method, the theory, process, calculating rules, advantages and shortcomings of traditional function point analysis method and COSMIC-FFP. On the basis of the above, this paper discusses the notional mapping of Use Case and COSMIC-FFP. Meanwhile this paper enumerates the three calculating rules at length. The author demonstrates a detailed example in allusion to Course Registration System. At the end of this paper, the author summarizes the results of deploying the UCD-FFP, and looks forward the perspectives of the following researching on it.