3 Terms, definitions, abbreviated terms, and conventions ToC Previous Next

3.3 Conventions used in this document ToC Previous Next

3.3.1 Conventions for Node descriptions ToC Previous Next

Node definitions are specified using tables (see Table 2).

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.
  • 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. 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 Objects and Variables.
  • The TypeDefinition column specifies a symbolic name for a NodeId, i.e. the specified Node points with a HasTypeDefinition Reference to the corresponding Node.
  • 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.

Note that if a symbolic name of a different namespace is used, it is prefixed by the NamespaceIndex (see Table 71).

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 part of this document points to their definition.

Table 2 illustrates the table. If no components are provided, the DataType, TypeDefinition and Other columns may be omitted and only a Comment column is introduced to point to the Node definition.

Table 2 – Type Definition Table

Attribute Value
Attribute name Attribute value. If it is an optional Attribute that is not set “–“ is used.
   
References NodeClass BrowseName DataType TypeDefinition Other
ReferenceType   name NodeClass   of the TargetNode. 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 “–“. DataType of the referenced Node, only applicable for Variables. TypeDefinition   of the referenced Node, only applicable for Variables and Objects. Additional characteristics of the TargetNode such as the ModellingRule or AccessLevel.
NOTE Notes referencing footnotes of the table content.          

Components of Nodes can be complex that is containing components by themselves. The TypeDefinition, NodeClass and DataType can be derived from the type definitions, and the symbolic name can be created as defined in Annex A. 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 AccessLevel has the CurrentRead bit set but not the CurrentWrite bit.
ReadWrite RW The Node AccessLevel has the CurrentRead and CurrentWrite bits set.
WriteOnly WO The Node AccessLevel has the CurrentWrite bit set but not the CurrentRead bit.

If multiple characteristics are defined, they are separated by commas. The name or the short name may be used.

3.3.1.1 Additional References ToC

To provide information about additional References, the format as shown in Table 4 is used.

Table 4 – <some>Type Additional References

SourceBrowsePath Reference Type Is Forward TargetBrowsePath
SourceBrowsePath is always relative to the TypeDefinition. Multiple elements are defined as separate rows of a nested table. ReferenceType   name True = forward Reference.    TargetBrowsePath points to another Node, which can be a well-known instance or a TypeDefinition. You can use BrowsePaths here as well, which is either relative to the TypeDefinition or absolute.If absolute, the first entry needs to refer to a type or well-known instance, uniquely identified within a namespace by the BrowseName.

References can be to any other Node.

3.3.1.2 Additional sub-components ToC

To provide information about sub-components, the format as shown in Table 5 is used.

Table 5 – <some>Type Additional Subcomponents

BrowsePath References NodeClass BrowseName DataType TypeDefinition Others
BrowsePath is always relative to the TypeDefinition. Multiple elements are defined as separate rows of a nested table NOTE Same as for Table 2          

3.3.1.3 Additional Attribute values ToC

The type definition table provides columns to specify the values for required Node Attributes for InstanceDeclarations. To provide information about additional Attributes, the format as shown in Table 6 is used.

Table 6 – <some>Type Attribute values for child Nodes

BrowsePath <Attribute name> Attribute
BrowsePath is always relative to the TypeDefinition. Multiple elements are defined as separate rows of a nested table    The values of attributes are converted to text by adapting the reversible JSON encoding rules defined in OPC 10000-6.    If the JSON encoding of a value is a JSON string or a JSON number then that value is entered in the value field. Double quotes are not included.   If the DataType includes a NamespaceIndex (QualifiedNames, NodeIds or ExpandedNodeIds) then the notation used for BrowseNames is used.   If the value is an Enumeration the name of the enumeration value is entered.   If the value is a Structure then a sequence of name and value pairs is entered. Each pair is followed by a newline. The name is followed by a colon. The names are the names of the fields in the DataTypeDefinition.   If the value is an array of non-structures then a sequence of values is entered where each value is followed by a newline.If the value is an array of Structures or a Structure with fields that are arrays or with nested Structures then the complete JSON array or JSON object is entered. Double quotes are not included.

There can be multiple columns to define more than one Attribute.

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