ISBSG variables most frequently used for software effort estimation: a mapping review

Background: The International Software Benchmarking Standards Group (ISBSG) dataset makes it possible to estimate a project's size, effort, duration, and cost. Aim: The aim was to analyze the ISBSG variables that have been used by researchers for software effort estimation from 2000, when the first papers were published, until the end of 2013. Method: A systematic mapping review was applied to over 167 papers obtained after the filtering process. From these, it was found that 133 papers produce effort estimation and only 107 list the independent variables used in the effort estimation models. Results: Seventy-one out of 118 ISBSG variables have been used at least once. There is a group of 20 variables that appear in more than 50% of the papers and include Functional Size (62%), Development Type (58%), Language Type (53%), and Development Platform (52%) following ISBSG recommendations. Sizing and Size attributes altogether represent the most relevant group along with Project attributes that includes 24 technical features of the project and the development platform. All in all, variables that have more missing values are used less frequently. Conclusions: This work presents a snapshot of the existing usage of ISBSG variables in software development estimation. Moreover, some insights are provided to guide future studies.