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.
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.
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.
namespace index
namespace uri
the parent node
returns the nodeId of this node's Type Definition
bind a variable with a get and set functions.
void
In this variation, the user provides a function that returns a Variant with the current value.
The sourceTimestamp will be set automatically.
The get function is called synchronously.
browse the node to extract information requested in browseDescription
an array with reference descriptions
the dispose method should be called when the node is no longer used, to release back pointer to the address space and clear caches.
the referenceType as a string.
the referenceType as a string.
an array with references
return an array with the Aggregates of this object.
retrieve a component by name
return an array with the components of this object.
return a array of the objects for which this node is an EventSource
return a array with the event source of this object.
return an array with the SubStates of this object.
retrieve a folder by name
returns the list of nodes that this folder object organizes
returns the method exposed by this object and with the given nodeId
returns the list of methods that this object provides
an array with Method objects.
Note: internally, methods are special types of components
return a array with the notifiers of this object.
return a array with the properties of this object.
retrieve a property by name
return an array with the SubStates of this object.
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
from OPC.UA.Spec 1.02 part 4 5.10.2.4 StatusCodes Table 51 defines values for the operation level statusCode contained in the DataValue structure of each values element. Common StatusCodes are defined in Table 166.
Table 51 Read Operation Level Result Codes
Symbolic Id Description
BadNodeIdInvalid The syntax of the node id is not valid. BadNodeIdUnknown The node id refers to a node that does not exist in the server address space. BadAttributeIdInvalid BadAttributeIdInvalid The attribute is not supported for the specified node. BadIndexRangeInvalid The syntax of the index range parameter is invalid. BadIndexRangeNoData No data exists within the range of indexes specified. BadDataEncodingInvalid The data encoding is invalid. This result is used if no dataEncoding can be applied because an Attribute other than Value was requested or the DataType of the Value Attribute is not a subtype of the Structure DataType. BadDataEncodingUnsupported The server does not support the requested data encoding for the node. This result is used if a dataEncoding can be applied but the passed data encoding is not known to the Server. BadNotReadable The access level does not allow reading or subscribing to the Node. BadUserAccessDenied User does not have permission to perform the requested operation. (table 165)
from OPC.UA.Spec 1.02 part 4 5.10.2.4 StatusCodes Table 51 defines values for the operation level statusCode contained in the DataValue structure of each values element. Common StatusCodes are defined in Table 166.
Read Operation Level Result Codes
| Symbolic Id | Description |
|---|---|
| BadNodeIdInvalid | The syntax of the node id is not valid. |
| BadNodeIdUnknown | The node id refers to a node that does not exist in the server address space. |
| BadAttributeIdInvalid | BadAttributeIdInvalid The attribute is not supported for the specified node. |
| BadIndexRangeInvalid | The syntax of the index range parameter is invalid. |
| BadIndexRangeNoData | No data exists within the range of indexes specified. |
| BadDataEncodingInvalid | The data encoding is invalid. This result is used if no dataEncoding can be applied because an Attribute other than Value was requested or the DataType of the Value Attribute is not a subtype of the Structure DataType. |
| BadDataEncodingUnsupported | The server does not support the requested data encoding for the node. This result is used if a dataEncoding can be applied but the passed data encoding is not known to the Server. |
| BadNotReadable | The access level does not allow reading or subscribing to the Node. |
| BadUserAccessDenied | User does not have permission to perform the requested operation. (table 165) |
setPermissions set the role and permissions
setValueFromSource is used to let the device sets the variable values this method also records the current time as sourceTimestamp and serverTimestamp. the method broadcasts an "value_changed" event
Undo the effect of propagate_back_references
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
A OPCUA Variable Node