This paper describes a decision support system to represent the semantics of legal norms. The focus is on designing and software- technical implementing of a comprehensive system to support model based reasoning on legal norms and enabling end-users to create, maintain, and analyze semantic models, i.e. ontologies, representing structure and semantics of norms.
A model based expression language (MxL) has been developed to coherently support the formalization of logical and arithmetical operations. MxL is intended to define complex, nested, strongly-typed, and functional operations. The paper summarizes research on the design and implementation of a legal expert system built upon model based decision structures. Thereby, three different components, namely a model store, a model execution component, and an interaction component have been developed. The formalization, execution, and analysis is shown on German child benefit regulations.