1. A data conversion system for converting first data to be processed in a first system into second data to be processed in a second system, comprising: means for receiving the first data from the first system; first converting means for converting the first data into first intermediate data in a first intermediate data format, the first intermediate data being equal in meaning to the first data; second converting means for converting the first intermediate data into second intermediate data in a second intermediate data format, the second intermediate data being equal in meaning to the second data; third converting means for converting the second intermediate data into the second data; and means for transmitting the second data to the second system.