Published data items – OPC Unified Architecture

6.2.11.1 Published data items

The configuration model defines different parameters that influence the information flow from Publisher to Subscriber in the case of a Bad Value Status or other error situations. Figure 25 depicts the parameters and the information flow inside a Publisher and inside a Subscriber.

The parameters and behaviour relevant for the encoding of a DataSetMessage on the Publisher side and the decoding of the DataSetMessage on the Subscriber side are defined in 6.2.4.2 together with the DataSetFieldContentMask.

The mapping of source value and status to the DataSet in the Publisher depends on the substitute value. The dependencies are defined in Table 79.

Table 79 – Source to message input mapping

Source		Substitute Value	DataSet Publisher side
Value ^(b)	Status ^(a)		Value	Status ^(a)
Value 1	Good_*	Value 2	Value 1	Good_*
Value 1	Uncertain_*		Value 1	Uncertain_*
Ignored	Bad_*		Value 2	Uncertain_SubstituteValue
Value 1	Good_*	Null	Value 1	Good_*
Value 1	Uncertain_*		Value 1	Uncertain_*
Ignored	Bad_*		Null	Bad_*
^(a) If no specific StatusCode is used, the grouping into severity Good, Uncertain or Bad is used. In this case, the resulting Status matches the input Status. ^(b) Any error that happens during processing of source value e.g. DataType does not match DataSetField should be treated like a Bad StatusCode received from the source.

The mapping of the decoded DataSet on the Subscriber side to the value and status of the target Variable depends on the override value. The dependencies are defined in Table 80.

Table 80 – Message output to target mapping

Decoded DataSet Subscriber		Override Value Handling Enum	Override Value	Reader State	Target
Value	Status ^(a)				Value	Status ^(a)
Value 1	Good_*	OverrideValue	Value 2	Operational	Value 1	Good_*
Value 1	Uncertain_*				Value 1	Uncertain_*
Ignored	Bad_*				Value 2	Good_LocalOverride
Value 1	Good_*	LastUsableValue	Ignored		Value 1	Good_*
Value 1	Uncertain_*				Value 1	Uncertain_*
Ignored	Bad_*				LastValue ^(b)	Uncertain_LastUsableValue
Value 1	Good_*	Disabled	Ignored		Value 1	Good_*
Value 1	Uncertain_*				Value 1	Uncertain_*
Ignored	Bad_*				Null	Bad_*
No message received. The target values are updated once after a reader state change.		OverrideValue	Value 2	Disabled Paused	Value 2	Good_LocalOverride
		LastUsableValue	Ignored		LastValue ^(b)	Uncertain_LastUsableValue
		Disabled	Ignored		Null	Bad_OutOfService
		OverrideValue	Value 2	Error	Value 2	Good_LocalOverride
		LastUsableValue	Ignored		LastValue ^(b)	Uncertain_LastUsableValue
		Disabled	Ignored		Null	Bad_NoCommunication
^(a) If no specific StatusCode is used, the grouping into severity Good, Uncertain or Bad is used. In this case, the resulting Status matches the input Status. ^(b) The last value is either the last received value or the default value for the data type if there was never a value received before.

If one of the target Variables in the SubscribedDataSet does not allow writing of the StatusCode and the OverrideValueHandling is set to Disabled, the DataSetReader shall indicate the configuration error by setting the DataSetReader state to Error. In all other configurations of OverrideValueHandling when the target Variable does not allow writing of the StatusCode, only the Value is transferred to the target Variable.

If a target Variable in the SubscribedDataSet does not allow writing of timestamp, any received timestamp shall not be used and only the received value shall be written to the target Variable.