The common Attributesof OPC UA Address Space Nodesand their mapping from IEC 61131-3 are defined in Table 26.

Table 26– Common Node Attributes

Attribute

Use

DataType

Description

NodeId

Mandatory

NodeId

The NodeIdis a unique identifier for a Nodein an OPC UA Address Space. The identifier is server specific and its format is not defined in this specification.

NodeClass

Mandatory

NodeClass

The NodeClassis Variable for all Ctrl Variables.

BrowseName

Mandatory

QualifiedName

The BrowseNameis a QualifiedNamecomposed of a name string and a namespace index. It is used to create paths that can be passed to the TranslateBrowsePathsToNodeIds Serviceto get the NodeIdof a Variable Node. This is typically used to get the NodeId of Variable in an Objectinstance based on the path known from the Objecttype. The BrowseNameis not used to display the name of the Node.

The name part is generated from the Ctrl Variablename.

The namespace part depends of the scope where the Variable is defined. Chapter 12.5describes the handling of namespaces.

DisplayName

Mandatory

LocalizedText

The DisplayNameis 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 DisplayNameis server specific if the server supports localization of Variablenames.

The DisplayNameis composed of the Ctrl Variablename and an empty LocaleIdstring 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 Descriptionmay correspond to the element Documentationof the element Variablein PLCopen XML.

WriteMask

Optional

UInt32

The WriteMaskprovides the optional information which attributes of the Nodecan be written by a client. This excludes the Value Attributewhere the access is described by the AccessLevel Attribute.

The value of this Attribute is server specific.

Servers only supporting the use cases Observationand Operationare typically setting this Attributeto 0 or are not providing this optional Attribute.

Servers supporting also the use cases Engineeringand Servicemay allow clients to change Node Attributes.

UserWriteMask

Optional

UInt32

The user specific settings for the WriteMask.