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

Shall reflect the NodeClass of the Node.

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:

image008.png

Figure 1 – OPC UA standard definitions

Additional definitions:

image009.png

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: