4.98. Traceability requires a clear and complete record of the decisions and assumptions made, and of the models, parameters and data used in arriving at a given set of results. Traceability also encompasses the possibility to trace back to the origin of the data and other information used in the safety case. Thus, a coherent referencing system supporting the safety case should be established. The records should include structured information on when, on what basis and by whom various decisions and assumptions were made, how these decisions and assumptions were implemented, what modelling tools were used, and what the ultimate sources are for the data.