a first electronic control apparatus and a second electronic control apparatus, which are mounted on a vehicle, the first electronic control apparatus comprising:

a first controller configured to execute a first operating system that operates a first application that controls a device mounted on the vehicle;

a first communication circuit configured to perform data communication with an outside of the first electronic control apparatus; and

a housing configured to contain the first controller and the first communication circuit, the second electronic control apparatus comprising:

a second controller configured to execute a second operating system that operates a second application that controls a device mounted on the vehicle; and

a second communication circuit configured to perform data communication with the first communication circuit,

wherein: the first communication circuit and the second communication circuit are communicatively connected with each other by a service bus;

the service bus is configured to bridge data between (i) an application layer and (ii) a presentation layer or a layer lower than the presentation layer to exchange data so that the first electronic control apparatus and the second electronic control apparatus can exchange the data as if they were one device;

the service bus includes a database for associating the data used in the application layer with the data used in the presentation layer or the layer lower than the presentation layer; and

the service bus performs data conversion between the application layer data and the presentation or lower layer data by referring to the database.