Abstract: A method and system for preventing error during data replication is provided. A replication entity model is used to represent data in a source and data in a target. One or more of a logical model, a directed relationship model or a state model may be provided to prevent error. The method and system may be applied to data migration and data synchronisation. The system comprises a transformation engine and a replication engine, wherein the replication engine is adapted to instruct the transformation engine to replicate each replication entity in turn. This may be based on the order dictated by the one or more directed relationships in the directed relationship model. Replication of a replication entity by the transformation engine comprises replicating data within one or more selected data structures of the source in one or more selected data structures of the target, the selection being based on the mapping between the replication entity model data in the source and data in the target.