Abstract
Business rules extraction is an important activity in situations in which a software system becomes obsolete and needs to be replaced by a newer system, since the replacing system needs to satisfy the business rules embedded in the legacy software system. In this paper, we investigate an approach in which the computational business rules of a legacy software system can be extracted given previously generated output of the system and without requiring access to the system's source code. Furthermore, extracted computational business rules are validated automatically with minimal involvement of domain experts through Test-Driven Development (TDD) such that test cases are constructed from historic output of the system. The proposed approach is applied to extract the computational business rules of a large-scale governmental payroll legacy software system. The study results demonstrate that the suggested approach extracted computational business rules van meet a substantial number of test cases. Thus, the efforts involving domain experts can be reduces to analyze such instances.