PubSubState state machine – OPC Unified Architecture

6.2.1 PubSubState state machine

The PubSubState is used to expose and control the operation of a PubSub component. It is an enumeration of the possible states. The enumeration values are described in Table 1.

Table 1 – PubSubState values

Name	Value	Description
Disabled	0	The PubSub component is configured but currently disabled.
Paused	1	The PubSub component is enabled but currently paused by a parent component. The parent component is either Disabled or Paused.
Operational	2	The PubSub component is operational.
Error	3	The PubSub component is in an error state.
PreOperational	4	The PubSub component is enabled but currently in the process to execute the steps necessary to enter the Operational state.

Figure 22 depicts the PubSub components that have a PubSub state and their parent-child relationship. State changes of children are based on changes of the parent state. The root of the hierarchy is the PublishSubscribe component.

Figure 22 – PubSub component state dependencies

Table 2 formally defines the transitions of the state machine.

Table 2 – PubSubState state machine

Source State	Target State	Trigger Description
Disabled	Paused	The component was successfully enabled but the parent component is in the state Disabled or Paused.
Disabled	PreOperational	The component was successfully enabled.
Paused	Disabled	The component was successfully disabled.
Paused	PreOperational	The state of the parent component changed to Operational.
PreOperational	Operational	The component completed the steps necessary to enter the Operational state. These steps include setup of network communication and security keys. If the PubSub component is a DataSetReader, the state shall change to Operational after the first key frame or event DataSetMessage was received.
PreOperational	Disabled	The component was successfully disabled.
PreOperational	Paused	The state of the parent component changed to Disabled or Paused.
PreOperational	Error	There is a pending error situation for the related PubSub component.
Operational	Disabled	The component was successfully disabled.
Operational	Paused	The state of the parent component changed to Disabled or Paused.
Operational	Error	There is a pending error situation for the related PubSub component.
Error	Disabled	The component was successfully disabled.
Error	Paused	The state of the parent component changed to Disabled or Paused.
Error	Operational	The error situation was resolved for the related PubSub component.
Error	PreOperational	The error situation was resolved for the related PubSub component.

The PubSubState representation in the AddressSpace is defined in Table 3.

Table 3 – PubSubState definition

Attribute	Value
BrowseName	PubSubState
IsAbstract	False

References	Node Class	BrowseName	DataType	TypeDefinition	Others
Subtype of Enumeration defined in OPC 10000-5
HasProperty	Variable	EnumStrings	LocalizedText []	PropertyType

Conformance Units
PubSub Model Base