Model-Based Simulation of Legal Requirements: Experience from Tax Policy Simulation

Using models for expressing legal requirements is now commonplace in Requirements Engineering. Models of legal requirements, on the one hand, facilitate communication between software engineers and legal experts, and on the other hand, provide a basis for systematic and automated analysis. The most prevalent application of legal requirements models is for checking the compliance of software systems with laws and regulations. In this experience paper, we explore a complementary application of legal requirements models, namely simulation. We observe that, in domains such as taxation, the same models that underlie legal compliance analysis bring important added value by enabling simulation. Concretely, this paper reports on the model-based simulation of selected legal requirements (policies) derived from Luxembourg's Income Tax Law. The simulation scenario considered in the paper is aimed at analyzing the impact of a current tax law reform proposal in Luxembourg. We describe our approach for simulation along with empirical results demonstrating the feasibility and accuracy of the approach. We further present lessons learned from the experience.