An Expert-Based Requirements Effort Estimation Model Using Bayesian Networks

[Motivation]: There are numerous software companies worldwide that split the software development life cycle into at least two separate projects – an initial project where a requirements specification document is prepared; and a follow-up project where the previously prepared requirements document is used as input to developing a software application. These follow-up projects can also be delegated to a third party, as occurs in numerous global software development scenarios. Effort estimation is one of the cornerstones of any type of project management; however, a systematic literature review on requirements effort estimation found hardly any empirical study investigating this topic. [Objective]: The goal of this paper is to describe an industrial case study where an expert-based requirements effort estimation model was built and validated for the Brazilian Navy. [Method]: A knowledge engineering of Bayesian networks process was employed to build the requirements effort estimation model. [Results]: The expert-based requirements effort estimation model was built with the participation of seven software requirements analysts and project managers, leading to 28 prediction factors and 30+ relationships. The model was validated based on real data from 11 large requirements specification projects. The model was incorporated into the Brazilian navy’s quality assurance process to be used by their software requirements analysts and managers. [Conclusion]: This paper details a case study where an expert-based requirements effort estimation model based solely on knowledge from requirements analysts and project managers was successfully built to help the Brazilian Navy estimate the requirements effort for their projects.