An avionics system including a first node and a second node wherein the first node is arranged to transmit a data message having: a data identifier, dynamic metadata associated with the data identifier and data content to the second node; wherein the second node is arranged to receive the data message from the first node and to: locate and read the data identifier within the data message; locate and read the dynamic metadata associated with the read data identifier; and retrieve data content from the determined position in the data message, wherein the data message contains multiple data identifiers, each with associated dynamic metadata and associated data content, and the second node is arranged only to locate and read the data identifier and dynamic metadata and retrieve data content in relation to a subset of the plurality of data identifiers.