IEC 62325-451-1:2017 specifies a UML package for the acknowledgment business process and its associated document contextual model, assembly model and XML schema for use within the European style electricity markets. The relevant aggregate core components (ACCs) defined in IEC 62325-351 have been contextualized into aggregated business information entities (ABIEs) to satisfy the requirements of the European style market acknowledgment business process. The contextualized ABIEs have been assembled into the acknowledgment document contextual model. This new edition includes the following significant technical changes with respect to the previous edition: - addition of an optional attribute ProcessType to the acknowledgement document to ease routing of incoming acknowledgement document instances to the appropriate application; - clarification of the activity diagram for the acknowledgement process; - addition of the list of constraints on datatypes.