Application of information-flow relations algorithm on extracting business rules from legacy code

Business rules are a set of conditional operations attached to a given data result. Over time, systems that implement business rules are updated when organizations change the data and operations to the changing business needs. On legacy systems, it is very difficult to extract business rules because of the inconsistency of documentation. So it is necessary to extract business rules from source code. Identifying domain variables is a significant step in extracting business rules from source code. This paper proposes a solution to identify domain variables automatically from source code by applying information-flow relations algorithm. The solution contains three steps: identifying variables affected by input domain variables; identifying variables, which affect output domain variables; domain variables management. It has been applied to a large complex financial legacy system, which has proved to be successful.