The Attributes of Nodes, their DataTypes and descriptions are defined in OPC 10000-3. Attributes not marked as optional are mandatory and shall be provided by a Server. The following tables define if the Attribute value is defined by this specification or if they vendor specific.
For all Nodes specified in this specification, the Attributes named in Table 3 shall be set as specified in the table.
Table 3 – Common Node Attributes
|
Attribute |
Value |
|
DisplayName |
The DisplayName is a LocalizedText. Each server shall provide the DisplayName identical to the BrowseName of the Node for the LocaleId “en”. Whether the server provides translated names for other LocaleIds is vendor specific. |
|
Description |
Optionally a vendor specific description is provided |
|
NodeClass |
|
|
NodeId |
The NodeId is described by BrowseNames as defined in 3.4.2.1 and defined in Annex A. |
|
WriteMask |
Optionally the WriteMask Attribute can be provided. If the WriteMask Attribute is provided, it shall set all Attributes to not writeable that are not said to be vendor-specific like Description, EventNotifier or DisplayName with a LocaleId other than ‘en’. For example, the Description Attribute may be set to writeable since a Server may provide a server-specific description for the Node. The Attributes NodeId, BrowseName and NodeClass and DataType shall not be writeable, because they are defined for each Node in this specification. The WriteMask Attribute does not take any user access rights into account, that is, although an Attribute is writeable this may be restricted to a certain user / user group. |
|
UserWriteMask |
Optionally the UserWriteMask Attribute can be provided. It takes the user access rights for the Session user into account. |
For all Objects specified in this specification, the Attributes named in Table 4 shall be set as specified in the table. The definitions for the Attributes can be found in OPC 10000-3.
Table 4 – Common Object Attributes
|
Attribute |
Value |
|
EventNotifier |
Indicates whether the Node can be used to subscribe to Events or not. The value of the Attribute is vendor specific. |
For all Variables specified in this specification, the Attributes named in Table 5 shall be set as specified in the table. The definitions for the Attributes can be found in OPC 10000-3.
Table 5 – Common Variable Attributes
|
Attribute |
Value |
|
MinimumSamplingInterval |
Optionally, a vendor-specific minimum sampling interval is provided |
|
AccessLevel |
The access level for Variables used for type definitions is vendor-specific, for all other Variables defined in this specification, the access level shall allow a current read; other settings are vendor specific. |
|
UserAccessLevel |
The value for the UserAccessLevel Attribute is vendor-specific. It is assumed that all Variables can be accessed by at least one user. |
|
Value |
For Variables used as InstanceDeclarations, the value is vendor-specific; otherwise it shall represent the value described in the text. |
|
ArrayDimensions |
If the ValueRank does not identify an array of a specific dimension (i.e. ValueRank <= 0) the ArrayDimensions can either be set to null or the Attribute is missing. This behaviour is vendor-specific. If the ValueRank specifies an array of a specific dimension (i.e. ValueRank > 0) then the ArrayDimensions Attribute shall be specified in the table defining the Variable. The concrete array length is contained in the delivered Value. Therefore this information is only relevant for write access to the Variable Value if the array has a fixed length. |
For all VariableTypes specified in this specification, the Attributes named in Table 6 shall be set as specified in the table. The definitions for the Attributes can be found in OPC 10000-3.
Table 6 – Common VariableType Attributes
|
Attributes |
Value |
|
Value |
Optionally a vendor-specific default value can be provided |
|
ArrayDimensions |
If the ValueRank does not identify an array of a specific dimension (i.e. ValueRank <= 0) the ArrayDimensions can either be set to null or the Attribute is missing. This behaviour is vendor-specific. If the ValueRank specifies an array of a specific dimension (i.e. ValueRank > 0) then the ArrayDimensions Attribute shall be specified in the table defining the VariableType. The concrete array length is contained in the delivered Value. Therefore this information is only relevant for write access to the VariableType Value if the array has a fixed length. |