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 it is server-specific.
For all Nodes specified in this specification, the Attributes named in Figure 5 shall be set as specified in the table.
Table 5 – 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 server-specific. |
|
Description |
Optionally a server-specific description is provided. |
|
NodeClass |
|
|
NodeId |
The NodeId is described by BrowseNames as defined in 3.4.2.1. |
|
WriteMask |
Optionally the WriteMask Attribute can be provided. If the WriteMask Attribute is provided, it shall set all non-server-specific Attributes to not writable. For example, the Description Attribute may be set to writable since a Server may provide a server-specific description for the Node. The NodeId shall not be writable, because it is defined for each Node in this specification. |
|
UserWriteMask |
Optionally the UserWriteMask Attribute can be provided. The same rules as for the WriteMask Attribute apply. |
|
RolePermissions |
Optionally server-specific role permissions can be provided. |
|
UserRolePermissions |
Optionally the role permissions of the current Session can be provided. The value is server-specifc and depend on the RolePermissions Attribute (if provided) and the current Session. |
|
AccessRestrictions |
Optionally server-specific access restrictions can be provided. |
For all Objects 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 Object Attributes
|
Attribute |
Value |
|
EventNotifier |
Whether the Node can be used to subscribe to Events or not is server-specific. |
For all Variables specified in this specification, the Attributes named in Table 7 shall be set as specified in the table. The definitions for the Attributes can be found in OPC 10000-3.
Table 7 – Common Variable Attributes
|
Attribute |
Value |
|
MinimumSamplingInterval |
Optionally, a server-specific minimum sampling interval is provided. |
|
AccessLevel |
The access level for Variables used for type definitions is server-specific, for all other Variables defined in this specification, the access level shall allow reading; other settings are server-specific. |
|
UserAccessLevel |
The value for the UserAccessLevel Attribute is server-specific. It is assumed that all Variables can be accessed by at least one user. |
|
Value |
For Variables used as InstanceDeclarations, the value is server-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 server-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. |
|
Historizing |
The value for the Historizing Attribute is server-specific. |
|
AccessLevelEx |
If the AccessLevelEx Attribute is provided, it shall have the bits 8, 9, and 10 set to 0, meaning that read and write operations on an individual Variable are atomic, and arrays can be partly written. |
For all VariableTypes specified in this specification, the Attributes named in Table 8 be set as specified in the table. The definitions for the Attributes can be found in OPC 10000-3.
Table 8 – Common VariableType Attributes
|
Attributes |
Value |
|
Value |
Optionally a server-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 server-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. |
For all Methods specified in this specification, the Attributes named in Table 9 shall be set as specified in the table. The definitions for the Attributes can be found in OPC 10000-3.
Table 9 – Common Method Attributes
|
Attributes |
Value |
|
Executable |
All Methods defined in this specification shall be executable (Executable Attribute set to “True”), unless it is defined differently in the Method definition. |
|
UserExecutable |
The value of the UserExecutable Attribute is server-specific. It is assumed that all Methods can be executed by at least one user. |
For the following illustrations, the legend is as follows:
Figure 1 – OPC UA standard definitions
Additional definitions:
Figure 2 – OPC UA and additional definitions
Table 10 describes the additional definitions.
Table 10 – Description of additional definitions
|
Node element |
Graphical representation |
Definition of node element |
|
Mandatory Object |
Rectangular Frame |
A mandatory object with its type definition |
|
Optional Object |
Rectangular bold dashed Frame |
An optional object with its type definition |
|
Mandatory Placeholder Object |
Rectangular bold Frame |
A mandatory placeholder for objects with its type definition |
|
Optional Placeholder Object |
Rectangular dotted Frame |
An optional placeholder for objects with its type definition |
|
ObjectType |
Rectangular Frame with shadow |
An object type with its type definition |
|
VariableType |
Rounded rectangular Frame with shadow |
A variable type with its type definition |
|
Mandatory Variable |
Rectangular Frame with rounded corners |
A mandatory variable with its type definition |
|
Optional Variable |
Dotted rectangular Frame with rounded corners |
An optional variable with its type definition |
In case of not supported Properties the following default shall be provided:
- Properties with DataType String: empty string
- Properties with DataType LocalizedText: empty text field
- RevisionCounter Property: - 1