Nodedefinitions are specified using tables (see Table 2 ).
Attributesare defined by providing the Attributename and a value, or a description of the value.
Referencesare defined by providing the ReferenceTypename, the BrowseNameof the TargetNodeand its NodeClass.
- If the TargetNodeis a component of the Nodebeing defined in the table the Attributesof the composed Nodeare defined in the same row of the table.
- The DataTypeis only specified for Variables; “[<number>]” indicates a single-dimensional array, for multi-dimensional arrays the expression is repeated for each dimension (e.g. [2][3] for a two-dimensional array). For all arrays the ArrayDimensionsis set as identified by <number> values. If no <number> is set, the corresponding dimension is set to 0, indicating an unknown size. If no number is provided at all the ArrayDimensionscan be omitted. If no brackets are provided, it identifies a scalar DataTypeand the ValueRankis set to the corresponding value (see OPC 10000-3). In addition, ArrayDimensionsis set to null or is omitted. If it can be Any or ScalarOrOneDimension, the value is put into “{<value>}”, so either “{Any}” or “{ScalarOrOneDimension}” and the ValueRankis set to the corresponding value (see OPC 10000-3) and the ArrayDimensionsis set to null or is omitted. Examples are given in Table 1 .
Table 1– Examples of DataTypes
|
Notation |
DataType |
ValueRank |
ArrayDimensions |
Description |
|
0:Int32 |
0:Int32 |
-1 |
omitted or null |
A scalar Int32. |
|
0:Int32[] |
0:Int32 |
1 |
omitted or {0} |
Single-dimensional array of Int32 with an unknown size. |
|
0:Int32[][] |
0:Int32 |
2 |
omitted or {0,0} |
Two-dimensional array of Int32 with unknown sizes for both dimensions. |
|
0:Int32[3][] |
0:Int32 |
2 |
{3,0} |
Two-dimensional array of Int32 with a size of 3 for the first dimension and an unknown size for the second dimension. |
|
0:Int32[5][3] |
0:Int32 |
2 |
{5,3} |
Two-dimensional array of Int32 with a size of 5 for the first dimension and a size of 3 for the second dimension. |
|
0:Int32{Any} |
0:Int32 |
-2 |
omitted or null |
An Int32 where it is unknown if it is scalar or array with any number of dimensions. |
|
0:Int32{ScalarOrOneDimension} |
0:Int32 |
-3 |
omitted or null |
An Int32 where it is either a single-dimensional array or a scalar. |
- The TypeDefinition is specified for Objectsand Variables.
- The TypeDefinition column specifies a symbolic name for a NodeId, i.e. the specified Nodepoints with a HasTypeDefinition Referenceto the corresponding Node.
- The ModellingRuleof the referenced component is provided by specifying the symbolic name of the rule in the ModellingRulecolumn. In the AddressSpace, the Nodeshall use a HasModellingRule Referenceto point to the corresponding ModellingRule Object.
If the NodeIdof a DataTypeis provided, the symbolic name of the Noderepresenting the DataTypeshall be used.
Note that if a symbolic name of a different namespace is used, it is prefixed by the NamespaceIndex(see 3.4.2.2).
Nodesof all other NodeClassescannot be defined in the same table; therefore only the used ReferenceType, their NodeClassand their BrowseNameare specified. A reference to another part of this document points to their definition.
Table 2illustrates the table. If no components are provided, the DataType, TypeDefinition and ModellingRule columns may be omitted and only a Comment column is introduced to point to the Nodedefinition.
Table 2– Type Definition Table
|
Attribute |
Value |
||||
|
Attribute name |
Attribute value. If it is an optional Attribute that is not set “--“ will be used. |
||||
|
|
|
||||
|
References |
NodeClass |
BrowseName |
DataType |
TypeDefinition |
Other |
|
ReferenceType name |
BrowseNameof the target Node. If the Referenceis to be instantiated by the server, then the value of the target Node’s BrowseName is “--“. |
DataType of the referenced Node, only applicable for Variables. |
TypeDefinitionof the referenced Node, only applicable for Variablesand Objects. |
Additional characteristics of the TargetNodesuch as the ModellingRuleor AccessLevel. |
|
|
NOTE Notes referencing footnotes of the table content. |
|||||
Components of Nodescan be complex that is containing components by themselves. The TypeDefinition, NodeClassand DataType can be derived from the type definitions, and the symbolic name can be created as defined in 3.4.3.1. Therefore, those containing components are not explicitly specified; they are implicitly specified by the type definitions.
The Other column defines additional characteristics of the Node. Examples of characteristics that can appear in this column are show in Table 3.
Table 3– Examples of Other Characteristics
|
Name |
Short Name |
Description |
|
0:Mandatory |
M |
The Node has the Mandatory ModellingRule. |
|
0:Optional |
O |
The Node has the Optional ModellingRule. |
|
0:MandatoryPlaceholder |
MP |
The Node has the MandatoryPlaceholder ModellingRule. |
|
0:OptionalPlaceholder |
OP |
The Node has the OptionalPlaceholder ModellingRule. |
|
ReadOnly |
RO |
The Node AccessLevelhas the CurrentReadbit set but not the CurrentWritebit. |
|
ReadWrite |
RW |
The Node AccessLevel has the CurrentRead and CurrentWrite bits set. |
|
WriteOnly |
WO |
The Node AccessLevel has the CurrentWritebit set but not the CurrentReadbit. |
If multiple characteristics are defined they are separated by commas. The name or the short name may be used.
The NodeIdsof all Nodesdescribed in this standard are only symbolic names. Annex Adefines the actual NodeIds.
The symbolic name of each Nodedefined in this document is its BrowseName, or, when it is part of another Node, the BrowseNameof the other Node, a “.”, and the BrowseNameof itself. In this case “part of” means that the whole has a HasPropertyor HasComponent Referenceto its part. Since all Nodesnot being part of another Nodehave a unique name in this document, the symbolic name is unique.
The NamespaceUrifor all NodeIdsdefined in this document is defined in Annex A. The NamespaceIndexfor this NamespaceUriis vendor-specific and depends on the position of the NamespaceUriin the server namespace table.
Note that this document not only defines concrete Nodes, but also requires that some Nodesshall be generated, for example one for each Sessionrunning on the Server. The NodeIdsof those Nodesare Server-specific, including the namespace. But the NamespaceIndexof those Nodescannot be the NamespaceIndexused for the Nodesdefined in this document, because they are not defined by this document but generated by the Server.
The text part of the BrowseNamesfor all Nodesdefined in this document is specified in the tables defining the Nodes. The NamespaceUrifor all BrowseNamesdefined in this document is defined in Annex A.
If the BrowseNameis not defined by this document, a namespace index prefix like ‘0:EngineeringUnits’ or ‘2:DeviceRevision’ is added to the BrowseName. This is typically necessary if a Propertyof another specification is overwritten or used in the OPC UA types defined in this document. Table 184provides a list of namespaces and their indexes as used in this document.
The Attributesof Nodes, their DataTypesand 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 Attributevalue is defined by this specification or if it is server-specific.
For all Nodesspecified in this specification, the Attributesnamed in Table 4shall be set as specified in the table.
Table 4– Common Node Attributes
|
Attribute |
Value |
|
DisplayName |
The DisplayNameis a LocalizedText. Each server shall provide the DisplayNameidentical to the BrowseNameof the Nodefor 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 NodeIdis described by BrowseNamesas defined in 3.4.2.1. |
|
WriteMask |
Optionally the WriteMask Attributecan be provided. If the WriteMask Attributeis provided, it shall set all non-server-specific Attributesto not writable. For example, the Description Attributemay be set to writable since a Servermay provide a server-specific description for the Node. The NodeIdshall not be writable, because it is defined for each Nodein this specification. |
|
UserWriteMask |
Optionally the UserWriteMask Attributecan be provided. The same rules as for the WriteMask Attributeapply. |
|
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-specific and depend on the RolePermissions Attribute(if provided) and the current Session. |
|
AccessRestrictions |
Optionally server-specific access restrictions can be provided. |
For all Objectsspecified in this specification, the Attributesnamed in Table 5shall be set as specified in the table. The definitions for the Attributescan be found in OPC 10000-3.
Table 5– Common Object Attributes
|
Attribute |
Value |
|
EventNotifier |
Whether the Nodecan be used to subscribe to Eventsor not is server-specific. |
For all Variablesspecified in this specification, the Attributesnamed in Table 6shall be set as specified in the table. The definitions for the Attributescan be found in OPC 10000-3.
Table 6– Common Variable Attributes
|
Attribute |
Value |
|
MinimumSamplingInterval |
Optionally, a server-specific minimum sampling interval is provided. |
|
AccessLevel |
The access level for Variablesused for type definitions is server-specific, for all other Variablesdefined in this specification, the access level shall allow reading; other settings are server-specific. |
|
UserAccessLevel |
The value for the UserAccessLevel Attributeis server-specific. It is assumed that all Variablescan be accessed by at least one user. |
|
Value |
For Variablesused as InstanceDeclarations,the value is server-specific; otherwise it shall represent the value described in the text. |
|
ArrayDimensions |
If the ValueRankdoes not identify an array of a specific dimension (i.e. ValueRank<= 0) the ArrayDimensionscan either be set to null or the Attributeis missing. This behavior is server-specific. If the ValueRankspecifies an array of a specific dimension (i.e. ValueRank> 0) then the ArrayDimensions Attributeshall be specified in the table defining the Variable. |
|
Historizing |
The value for the Historizing Attributeis server-specific. |
|
AccessLevelEx |
If the AccessLevelEx Attributeis provided, it shall have the bits 8, 9, and 10 set to 0, meaning that read and write operations on an individual Variableare atomic, and arrays can be partly written. |
For all VariableTypesspecified in this specification, the Attributesnamed in Table 7shall be set as specified in the table. The definitions for the Attributescan be found in OPC 10000-3.
Table 7– Common VariableType Attributes
|
Attributes |
Value |
|
Value |
Optionally a server-specific default value can be provided. |
|
ArrayDimensions |
If the ValueRankdoes not identify an array of a specific dimension (i.e. ValueRank<= 0) the ArrayDimensionscan either be set to null or the Attributeis missing. This behavior is server-specific. If the ValueRankspecifies an array of a specific dimension (i.e. ValueRank> 0) then the ArrayDimensions Attributeshall be specified in the table defining the VariableType. |
For all Methodsspecified in this specification, the Attributesnamed in Table 8shall be set as specified in the table. The definitions for the Attributescan be found in OPC 10000-3.
Table 8– Common Method Attributes
|
Attributes |
Value |
|
Executable |
All Methodsdefined in this specification shall be executable (Executable Attributeset to “True”), unless it is defined differently in the Methoddefinition. |
|
UserExecutable |
The value of the UserExecutable Attributeis server-specific. It is assumed that all Methodscan be executed by at least one user. |