Method for changing a data format of communication data of a device communication provided between a first communication partner and a second communication partner, wherein a change is to be made from a source data format to a target data format, wherein the respective communication partner (11, 12) is configured in such a way that it converts memory data of a respective local data memory that is to be transmitted on the basis of a first metamodel file by means of a first serializer into the source data format and transmits the memory data converted into the source data format as communication data, wherein the first metamodel file defines all structural elements of a message type assigned to the first metamodel file that are to be transmitted in the source data format, and wherein a second metamodel file is generated by a processor device from the first metamodel file by means of a transformation rule, the respective structural element of the first metamodel file being assigned to a respective corresponding structural element (S') using the transformation rule, so that the second metamodel file defines all structural elements (S') of the message type that are to be transmitted in the target data format, and in the respective communication partner (11, 12) its first serializer is replaced by a second serializer for the target data format and its first metamodel file is replaced by the second metamodel file, wherein the first data format is an XML format and an XSD file is used as the basis for the first metamodel file, and the second data format is a protobuf format and a protobuf definition file is generated as second metamodel file, and thereby a data tree is defined by the first metamodel file and the data tree is traversed recursively by the processor device and a structural element (S') is generated for each leaf of the tree, characterised in that list elements specified according to XSD syntax by the attribute maxOccurs="unbounded" are modeled in the proto file by the field modifier "repeated", and a functional range of a list with a limited number of list elements is retained, in that only the first metamodel file provides a list with list elements limited to a maximum number as structural element and the list in the second metamodel file is mapped to a list with an unlimited number of list elements by the transformation rule, but in addition program data with program instructions for a storage routine are provided for the respective communication partner (11, 12), by means of which, when the second metamodel file is used, the list is limited to the maximum number of list elements by terminating the transmission of the list when the maximum number is reached. the respective communication partner (11, 12) is configured in such a way that it converts memory data of a respective local data memory that is to be transmitted on the basis of a first metamodel file by means of a first serializer into the source data format and transmits the memory data converted into the source data format as communication data, wherein the first metamodel file defines all structural elements of a message type assigned to the first metamodel file that are to be transmitted in the source data format, and wherein a second metamodel file is generated by a processor device from the first metamodel file by means of a transformation rule, the respective structural element of the first metamodel file being assigned to a respective corresponding structural element (S') using the transformation rule, so that the second metamodel file defines all structural elements (S') of the message type that are to be transmitted in the target data format, and in the respective communication partner (11, 12) its first serializer is replaced by a second serializer for the target data format and its first metamodel file is replaced by the second metamodel file, wherein the first data format is an XML format and an XSD file is used as the basis for the first metamodel file, and the second data format is a protobuf format and a protobuf definition file is generated as second metamodel file, and thereby a data tree is defined by the first metamodel file and the data tree is traversed recursively by the processor device and a structural element (S') is generated for each leaf of the tree, characterised in that list elements specified according to XSD syntax by the attribute maxOccurs="unbounded" are modeled in the proto file by the field modifier "repeated", and a functional range of a list with a limited number of list elements is retained, in that only the first metamodel file provides a list with list elements limited to a maximum number as structural element and the list in the second metamodel file is mapped to a list with an unlimited number of list elements by the transformation rule, but in addition program data with program instructions for a storage routine are provided for the respective communication partner (11, 12), by means of which, when the second metamodel file is used, the list is limited to the maximum number of list elements by terminating the transmission of the list when the maximum number is reached.