The parameter dataIdentifier (DID) logically represents an object (e.g., Air Inlet Door Position) or collection of objects. This parameter shall be available in the server's memory. The dataIdentifier value shall either exist in fixed memory or temporarily stored in RAM if defined dynamically by the service dynamicallyDefineDataIdentifier. In general, a dataIdentifier is capable of being utilized in many diagnostic service requests including 0x22 (readDataByIdentifier), 0x2E (writeDataByIdentifier), and 0x2F (inputOutputControlByIdentifier). A dataIdentifier is also used in various diagnostic service responses (e.g., positive response to service 0x19 subfunction readDTCSnapshotRecordByDTCNumber).
IMPORTANT — Regardless of which service a dataIdentifier is used with, it shall consistently
represent the same thing (i.e., a given object with a given size / meaning / etc.) on a given ECU.