The common Attributes of OPC UA Address Space Nodes and their mapping from IEC 61131-3 are defined in Table 26.
Table 26 – Common Node Attributes
|
Attribute |
Use |
DataType |
Description |
|
NodeId |
Mandatory |
NodeId |
The NodeId is a unique identifier for a Node in an OPC UA Address Space. The identifier is server specific and its format is not defined in this specification. |
|
NodeClass |
Mandatory |
NodeClass |
The NodeClass is Variable for all Ctrl Variables. |
|
BrowseName |
Mandatory |
QualifiedName |
The BrowseName is a QualifiedName composed of a name string and a namespace index. It is used to create paths that can be passed to the TranslateBrowsePathsToNodeIds Service to get the NodeId of a Variable Node. This is typically used to get the NodeId of Variable in an Object instance based on the path known from the Object type. The BrowseName is not used to display the name of the Node. The name part is generated from the Ctrl Variable name. The namespace part depends of the scope where the Variable is defined. Chapter 12.5 describes the handling of namespaces. |
|
DisplayName |
Mandatory |
LocalizedText |
The DisplayName is a LocalizedText used by clients to display the name of a Node. It is composed of a localized text part and a LocaleId identifying the language of the text. The DisplayName is server specific if the server supports localization of Variable names. The DisplayName is composed of the Ctrl Variable name and an empty LocaleId string if the server does not support localization. |
|
Description |
Optional |
LocalizedText |
The optional Description shall describe the meaning of the Node using a localized text. The Description may correspond to the element Documentation of the element Variable in PLCopen XML. |
|
WriteMask |
Optional |
UInt32 |
The WriteMask provides the optional information which attributes of the Node can be written by a client. This excludes the Value Attribute where the access is described by the AccessLevel Attribute. The value of this Attribute is server specific. Servers only supporting the use cases Observation and Operation are typically setting this Attribute to 0 or are not providing this optional Attribute. Servers supporting also the use cases Engineering and Service may allow clients to change Node Attributes. |
|
UserWriteMask |
Optional |
UInt32 |
The user specific settings for the WriteMask. |