# deviceId

val deviceId: String? = null

It allows a unique identification of a data pair, between a Sale System/Terminal and a POI System/Terminal during period of time, typically one day. This identifier is mandatory for messages of the "Device" MessageClass. For the Device Dialogue (i.e. device request coming from the sale outside a service request/response), DeviceID identifies alone the device data pair. For the Device Dialogue (i.e. device request sent inside a service request/response), DeviceID identifies the device data pair inside the "Service" data pair identified by ServiceID. This identifier is absent for messages of "Service", and "Event" MessageClass. The ServiceID of the data response is always the same value than the ServiceID of the data request. This identifier allows the recognition of duplicate data and association of a data response to its data request. Value of DeviceID could be a structured string of alpha characters, for instance with a prefix to easily distinguish a particular sequence of messages.