The parameter set of a device (offline and online) is described by means of the DataInfo data type (available with the <GetDataInfo> method from IInstanceData (offline) and IDeviceData (online)).

DataInfo provides a description of the available data without the values. The actual values are accessible with <Read> and <Write> methods from IInstanceData (offline) and IDeviceData (online).

DataInfo provides a list of data items (member DeviceDataItems), which may represent a range of types. Some of these data items are mapped to DataVariables (see Table 68).

Table 68 – Mapping of FDT data items

OPC	FDT
DataVariable(according OPC UA 10000-3)	Data
	UnitData
	RangeData
	AlarmData
	SubstituteData
	StructDataGroup
FunctionalGroup (according OPC UA 10000-100)	DataGroup
Block object (according OPC UA 10000-100)	ModuleDataGroup