The AccessLevel Attribute is used to indicate how the Value of a Variable can be accessed (read/write) and if it contains current and/or historic data.
The AccessLevel does not take any user access rights into account, i.e. although the Variable is writable this may be restricted to a certain user / user group.
The {{link:AccessLevelType}}
This Attribute specifies the length of each dimension for an array value.
valueRank Attribute.valueRank <=0.example
For example, if a Variable is defined by the following javascript array with 346 Int32 elements:
const myArray = new Array(346).fill(0);
then:
DataType would point to an Int32
the Variable's valueRank has the value 1 and,
the arrayDimensions is an array with one entry having the value 346.
{
dataType: "Int32",
valueRank: 1,
arrayDimensions: [346]
}Note: the maximum length of an array transferred on the wire is 2147483647 (max Int32) and a multidimensional array is encoded as a one dimensional array.
effective display name
contains a human readable name for the current state of the state machine after taking the state of any SubStateMachines in account. There is no rule specified for which state or sub-state should be used. It is up to the Server and will depend on the semantics of the StateMachineType
The historizing attribute indicates whether the server is actively collecting data for the
history of the variable.
This differs from the accessLevel Attribute which identifies if the variable has any historical data.
A value of true indicates that the server is actively collecting data.
A value of false indicates the server is not actively collecting data.
Default value is false.
The MinimumSamplingInterval Attribute indicates how 'current' the Value of the Variable will be kept.
It specifies (in milliseconds) how fast the Server can reasonably sample the value for changes (see Part 4 for a detailed description of sampling interval).
A MinimumSamplingInterval of 0 indicates that the Server is to monitor the item continuously.
A MinimumSamplingInterval of -1 means indeterminate.
NodeVersion (Optional) String The NodeVersion Property is used to indicate the version of a Node. The NodeVersion Property is updated each time a Reference is added or deleted to the Node the Property belongs to. Attribute value changes do not cause the NodeVersion to change. Clients may read the NodeVersion Property or subscribe to it to determine when the structure of a Node has changed.
number is an integer which uniquely identifies the current state within the StateMachineType
The UserAccessLevel Attribute is used to indicate how the Value of a Variable can be accessed (read/write) and if it contains current or historic data taking user access rights into account.
The AccessLevelType is defined in 8.57.
This Attribute indicates whether the Value Attribute of the Variable is an array and how many dimensions the array has. It may have the following values:
n > 1 : the Value is an array with the specified number of dimensions.
OneDimension (1): The value is an array with one dimension.
OneOrMoreDimensions (0): The value is an array with one or more dimensions.
Scalar (-1): The value is not an array.
Any (-2): The value can be a scalar or an array with any number of dimensions.
ScalarOrOneDimension (-3): The value can be a scalar or a one dimensional array.
NOTE:
All DataTypes are considered to be scalar, even if they have array-like semantics like ByteString and String.
browse the node to extract information requested in browseDescription
return a complete name of this object by pre-pending name of its parent(s) to its own name
return a array of the objects for which this node is an EventSource nodes = HasEventSource => self
return a array with the event source of this object. self = HasEventSource => nodes
returns true if the accessLevel flag allows the variable to be readable in the specified context.
returns true if the userAccessLevel flag allows the variable to be readable in the specified context.
returns true if the userAccessLevel flag allows the variable to be writeable in the specified context.
returns true if the accessLevel flag allows the variable to be writeable in the specified context.
this methods propagates the forward references to the pointed node by inserting backward references to the counter part node
write a variable attribute (callback version)
example
const writeValue = {
attributeId: AttributeIds.Value,
dataValue: new DataValue({
statusCode: StatusCodes.Good,
sourceTimestamp: new Date(),
value: new Variant({ dataType: DataType.Double, value: 3.14 })
}),
nodeId
};
myVariable.writeAttribute(context,writeValue,(err, statusCode) => {
if (err) { console.log("Write has failed"); return; }
console.log("write statusCode = ",statusCode.toString());
});write a variable attribute (async/await version)
example
try {
const writeValue = {
attributeId: AttributeIds.Value,
dataValue: new DataValue({
statusCode: StatusCodes.Good,
sourceTimestamp: new Date(),
value: new Variant({ dataType: DataType.Double, value: 3.14 })
}),
nodeId
};
const statusCode = await myVariable.writeAttribute(context,writeValue);
} catch(err) {
console.log("Write has failed");
return;
}
console.log("write statusCode = ", statusCode.toString());Generated using TypeDoc
https://reference.opcfoundation.org/v104/Core/docs/Part9/5.2/
https://reference.opcfoundation.org/v104/Core/VariableTypes/TwoStateVariableType/
https://reference.opcfoundation.org/v104/Core/ReferenceTypes/HasFalseSubState/