1. A data processing method comprising: receiving a message that includes a data part, a specification part indicating specifications to process the data part, and a program part containing an instruction to execute processing with the specifications indicated by the specification part; deciding the specification part indicating the specifications of processing to be executed by the instruction executed when executing the instruction contained in the program part of the received message; and processing the data part by the specifications indicated by the specification part in the message, which is decided to indicate the specifications of processing to be executed by the executed instruction.