Data, as distinct from software and hardware, has been a contributing factor in many accidents and incidents. The inclusion of data as a potential cause of harm is a crucial part of a thorough system saety assessment. This book has been developed by the Safety Critical Systems Club Data Safety Initiative Working Group (DSIWG) to provide guidance on how data should be managed in a safety-related context. This new version builds on the Data Safety Principles developed in earlier editions, provides a framework Data Safety Management Process and guidance on tailoring.