1.2.4 OcaNumericObserver

Class Hirarchy:

OcaRootOcaAgentOcaNumericObserver

class OcaNumericObserver : OcaAgent

Observer of a scalar numeric or boolean property (“target property”) of a specified object. Does not work for array, list, map, struct, or string properties. OcaNumericObserver emits an Observation event under certain conditions. There are three kinds of conditions:

  • Numeric comparison . The target property value meets a certain

comparison condition. A selection of comparison operators is available. Such observations are called “asynchronous observations”.

  • Timer expiry . The value of the Period property, if nonzero,

is a the time interval for the recurrent timed emission of Observation events. Such events (“periodic observations”) are emitted regardless of the target property’s value.

  • Combination of (1) and (2) . If a numeric comparison and a

nonzero period are both specified, then the Observation event is emitted when the timer expires and the numeric comparison is true. Such observations are called “conditional-periodic observations”. This is a weakly typed class. Its threshold is specified as an OcaFloat64 number.

  • For unsigned integer targets, the threshold and target are both

coerced to OcaUint64 before comparing.

  • For signed integer targets, the threshold and target are both

coerced to OcaInt64 before comparing.

  • For boolean values, the threshold hreshold and target are both

coerced to OcaUint8 , True is assigned the value One, False is assigned the value Zero. Note that this coercion may result in rounding errors if the observed datatype is of type OcaUint64 or OcaUint64. An OcaNumericObserver instance and the property it observes are bound at the time the OcaNumericObserver instance is constructed. For static devices, construction will occur during manufacture, or possibly during a subsequent hardware configuration step. For reconfigurable devices, construction might be done by online controllers as part of device configuration sessions. This class is normally used for monitoring readings of sensor readings, but may be used equally well for watching workers’ parameter settings.

Properties:

OcaClassID ClassID

Number that uniquely identifies the class. Note that this differs from the object number, which identifies the instantiated object. This property is an override of the OcaRoot property.

This property has id 3.1.

OcaClassVersionNumber ClassVersion

Identifies the interface version of the class. Any change to the class definition leads to a higher class version. This property is an override of the OcaRoot property.

This property has id 3.2.

OcaObserverState State

State: triggered, not triggered

This property has id 3.1.

OcaProperty ObservedProperty

Identification of the property being observed.

This property has id 3.2.

OcaFloat64 Threshold

Comparison value for raising the Triggered event.

This property has id 3.3.

OcaRelationalOperator Operator

Relational operator used when comparing the value of the observed property to the threshold value.

This property has id 3.4.

OcaBoolean TwoWay

True to emit a Triggered event upon crossing the threshold in either direction; false to emit only upon crossing in the primary direction (i.e. rising when Operator is set to _GreaterThan_ or _GreaterThanOrEqual_ ; falling when Operator is set to _LessThan_ or _LessThanOrEqual_ ; equality when Operator is set to _Equality_ ; inequality when Operator is set to _Inequality_ ).

This property has id 3.5.

OcaFloat64 Hysteresis

Hysteresis that is used when observing the property value. This indicates which amount must be added/subtracted from the Threshold value to raise or re-enable the Triggered event of this OcaObserver object. The rules for hysteresis handling depend upon the configured Operator and TwoWay properties. The Hysteresis property is ignored if the Operator property is ‘Inequality’.

This property has id 3.6.

OcaTimeInterval Period

Repetition period or zero. If nonzero, the observer will retrieve the value and emit

This property has id 3.7.

Properties inherited from OcaAgent:

Properties inherited from OcaRoot:

Methods:

OcaStatus GetLastObservation(OcaFloat64 &Observation)

Gets the value of the observed property that was reported by the most recently emitted Observation event. If the numeric observer has never emitted an Observation event, returns the IEEE not-a-number value. The return status indicates whether the value has been successfully returned.

This method has id 3.1.

Parameters

OcaFloat64 Observation – Output parameter.

OcaStatus GetState(OcaObserverState &state)

Gets the observer’s state. The return value indicates whether the state was successfully retrieved.

This method has id 3.2.

Parameters

OcaObserverState state – Output parameter.

OcaStatus GetObservedProperty(OcaProperty &property)

Gets the identification of the property that the observer observes. The return value indicates whether the identification was successfully retrieved.

This method has id 3.3.

Parameters

OcaProperty property – Output parameter.

OcaStatus SetObservedProperty(OcaProperty property)

Sets the identification of the property that the observer observes. The return value indicates whether the identification was successfully set.

This method has id 3.4.

Parameters

OcaProperty property – Input parameter.

OcaStatus GetThreshold(OcaFloat64 &Threshold)

Gets the value of the Threshold property. The return value indicates whether the threshold value was successfully retrieved.

This method has id 3.5.

Parameters

OcaFloat64 Threshold – Output parameter.

OcaStatus SetThreshold(OcaFloat64 Threshold)

Sets the value of the Threshold property. The return value indicates whether the threshold value was successfully set.

This method has id 3.6.

Parameters

OcaFloat64 Threshold – Input parameter.

OcaStatus GetOperator(OcaRelationalOperator &operator)

Gets the value of the Operator property. The return value indicates whether the property was successfully retrieved.

This method has id 3.7.

Parameters

OcaRelationalOperator operator – Output parameter.

OcaStatus SetOperator(OcaRelationalOperator operator)

Sets the value of the Operator property. The return value indicates whether the operator was successfully set.

This method has id 3.8.

Parameters

OcaRelationalOperator operator – Input parameter.

OcaStatus GetTwoWay(OcaBoolean &twoWay)

Gets the value of the TwoWay property. The return value indicates whether the property was successfully retrieved.

This method has id 3.9.

Parameters

OcaBoolean twoWay – Output parameter.

OcaStatus SetTwoWay(OcaBoolean twoWay)

Sets the value of the TwoWay property. The return value indicates whether the property was successfully set.

This method has id 3.10.

Parameters

OcaBoolean twoWay – Input parameter.

OcaStatus GetHysteresis(OcaFloat64 &hysteresis)

Gets the value of the Hysteresis property. The return value indicates whether the property was successfully retrieved.

This method has id 3.11.

Parameters

OcaFloat64 hysteresis – Output parameter.

OcaStatus SetHysteresis(OcaFloat64 hysteresis)

Sets the value of the Hysteresis property. The return value indicates whether the property was successfully set.

This method has id 3.12.

Parameters

OcaFloat64 hysteresis – Input parameter.

OcaStatus GetPeriod(OcaTimeInterval &period)

Gets the value of the Period property. The return value indicates whether the property was successfully retrieved.

This method has id 3.13.

Parameters

OcaTimeInterval period – Output parameter.

OcaStatus SetPeriod(OcaTimeInterval period)

Sets the value of the Period property. The return value indicates whether the property was successfully set.

This method has id 3.14.

Parameters

OcaTimeInterval period – Input parameter.

Methods inherited from OcaAgent:

Methods inherited from OcaRoot:

Events:

void Observation(OcaObservationEventData eventData)

Event emitted to signal an asynchronous, periodic, or conditional-periodic observation.