Node definitions are specified using tables (See Table 1)
Table 1 – Type Definition Table
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Attribute |
Value |
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Attribute name |
Attribute value. If it is an optional Attribute that is not set “--“ will be used. |
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References |
NodeClass |
BrowseName |
DataType |
TypeDefinition |
ModellingRule |
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ReferenceType name |
BrowseName of the target Node. If the Reference is to be instantiated by the server, then the value of the target Node’s BrowseName is “--“. |
Attributes of the referenced Node, only applicable for Variables and Objects.
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Referenced ModellingRule of the referenced Object. |
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Notes – Notes referencing footnotes of the table content. |
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Attributes are defined by providing the Attribute name and a value, or a description of the value.
References are defined by providing the ReferenceType name, the BrowseName of the TargetNode and its NodeClass.
- If the TargetNode is a component of the Node being defined in the table the Attributes of the composed Node are defined in the same row of the table. That implies that the referenced Node has a HasModelParent Reference with the Node defined in the Table as TargetNode (see OPC 10000-3 for the definition of ModelParents).
- The DataType is 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 ArrayDimensions is 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 ArrayDimensions can be omitted. If no brackets are provided, it identifies a scalar DataType and the ValueRank is set to the corresponding value (see OPC 10000-3). In addition, ArrayDimensions is 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 ValueRank is set to the corresponding value (see OPC 10000-3) and the ArrayDimensions is set to null or is omitted. In Table 2 examples are given.
Table 2 – Examples of DataTypes
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Notation |
DataType |
ValueRank |
ArrayDimensions |
Description |
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Int32 |
Int32 |
-1 |
omitted or NULL |
A scalar Int32 |
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Int32[] |
Int32 |
1 |
omitted or {0} |
Single-dimensional array of Int32 with an unknown size |
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Int32[][] |
Int32 |
2 |
omitted or {0,0} |
Two-dimensional array of Int32 with unknown sizes for both dimensions |
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Int32[3][] |
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 |
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Int32[5][3] |
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 |
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Int32{Any} |
Int32 |
-2 |
omitted or NULL |
An Int32 where it is unknown if it is scalar or array with any number of dimensions |
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Int32{ScalarOrOneDimension} |
Int32 |
-3 |
omitted or NULL |
An Int32 where it is either a single-dimensional array or a scalar |
- The TypeDefinition is specified for Objects and Variables.
- The TypeDefinition column specifies a NodeId of a TypeDefinitionNode, i.e. the specified Node points with a HasTypeDefinition Reference to the corresponding TypeDefinitionNode. The symbolic name of the NodeId is used in the table.
- The ModellingRule of the referenced component is provided by specifying the symbolic name of the rule in the ModellingRule column. In the AddressSpace, the Node shall use a HasModellingRule Reference to point to the corresponding ModellingRule Object.
If the NodeId of a DataType is provided, the symbolic name of the Node representing the DataType shall be used.
Nodes of all other NodeClasses cannot be defined in the same table; therefore only the used ReferenceType, their NodeClass and their BrowseName are specified. A reference to another of this document points to their definition.
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 Node definition.
Components of Nodes can be complex, i.e. containing components by themselves. The TypeDefinition, NodeClass, DataType and ModellingRule can be derived from the type definitions, and the symbolic name can be created as defined in 3.3.3.1. Therefore those containing components are not explicitly specified; they are implicitly specified by the type definitions.