UA Part 9: Alarms and Conditions - 5.8.12 Exclusive Limit Types

Errata exists for this version of the document.

This clause describes the state machine and the base Alarm Type behaviour for Alarm ConditionTypes with multiple mutually exclusive limits.

5.8.12.2 ExclusiveLimitStateMachineType

The ExclusiveLimitStateMachineType defines the state machine used by AlarmConditionTypes that handle multiple mutually exclusive limits. It is illustrated in Figure 17.

Figure 17 – ExclusiveLimitStateMachineType

It is created by extending the FiniteStateMachineType. It is formally defined in Table 61 and the state transitions are described in Table 62.

Table 61 – ExclusiveLimitStateMachineType definition

Attribute	Value
BrowseName	ExclusiveLimitStateMachineType
IsAbstract	False
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the FiniteStateMachineType
HasComponent	Object	HighHigh		StateType
HasComponent	Object	High		StateType
HasComponent	Object	Low		StateType
HasComponent	Object	LowLow		StateType
HasComponent	Object	LowToLowLow		TransitionType
HasComponent	Object	LowLowToLow		TransitionType
HasComponent	Object	HighToHighHigh		TransitionType
HasComponent	Object	HighHighToHigh		TransitionType

Table 62 – ExclusiveLimitStateMachineType transitions

BrowseName	References	BrowseName	TypeDefinition

Transitions
HighHighToHigh	FromState	HighHigh	StateType
	ToState	High	StateType
	HasEffect	AlarmConditionType
HighToHighHigh	FromState	High	StateType
	ToState	HighHigh	StateType
	HasEffect	AlarmConditionType
LowLowToLow	FromState	LowLow	StateType
	ToState	Low	StateType
	HasEffect	AlarmConditionType
LowToLowLow	FromState	Low	StateType
	ToState	LowLow	StateType
	HasEffect	AlarmConditionType

The ExclusiveLimitStateMachineType defines the sub state machine that represents the actual level of a multilevel Alarm when it is in the Active state. The sub state machine defined here includes High, Low, HighHigh and LowLow states. This model also includes in its transition state a series of transition to and from a parent state, the inactive state. This state machine as it is defined shall be used as a sub state machine for a state machine which has an Active state. This Active state could be part of a “level” Alarm or “deviation” Alarm or any other Alarm state machine.

The LowLow, Low, High, HighHigh are typical for many industries. Vendors can introduce sub-state models that include additional limits; they may also omit limits in an instance. If a model omits states or transitions in the StateMachine, it is recommended that they provide the optional Property AvailableStates and/or AvailableTransitions (see OPC 10000-5).

5.8.12.3 ExclusiveLimitAlarmType

The ExclusiveLimitAlarmType is used to specify the common behaviour for Alarm Types with multiple mutually exclusive limits. The ExclusiveLimitAlarmType is illustrated in Figure 18.

Figure 18 – ExclusiveLimitAlarmType

The ExclusiveLimitAlarmType is formally defined in Table 63.

Table 63 – ExclusiveLimitAlarmType definition

Attribute	Value
BrowseName	ExclusiveLimitAlarmType
IsAbstract	False
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the LimitAlarmType defined in clause 5.8.11.
HasSubtype	ObjectType	ExclusiveLevelAlarmType	Defined in Clause 5.8.14.3
HasSubtype	ObjectType	ExclusiveDeviationAlarmType	Defined in Clause 5.8.15.3
HasSubtype	ObjectType	ExclusiveRateOfChangeAlarmType	Defined in Clause 5.8.16.3
HasComponent	Object	LimitState		ExclusiveLimitStateMachineType	Mandatory

The LimitState is a sub state of the ActiveState and has an IsTrueSubStateOf reference to the ActiveState. The LimitState represents the actual limit that is violated in an instance of ExclusiveLimitAlarmType. When the ActiveState of the AlarmConditionType is inactive the LimitState shall not be available and shall return NULL on read. Any Events that subscribe for fields from the LimitState when the ActiveState is inactive shall return a NULL for these unavailable fields.