3.4.1 Conventions for Node descriptions
3.4.1.1 Node definitions

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.

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 3.4.2.2).

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 ModellingRule columns may be omitted and only a Comment column is introduced to point to the Node definition.

Each Type Node or well-known Instance Node defined shall have one or more ConformanceUnits defined in 11.1 that require the Node to be in the AddressSpace.

The relations between Nodes and ConformanceUnits are defined at the end of the tables defining Nodes, one row per ConformanceUnit. The ConformanceUnits are reflected in the Category element for the Node definition in the UANodeSet (see OPC 10000-6).

The list of ConformanceUnits in the UANodeSet allows Servers to optimize resource consumption by using a list of supported ConformanceUnits to select a subset of the Nodes in an Information Model.

When a Node is selected in this way, all dependencies implied by the References are also selected.

Dependencies exist if the Node is the source of HasTypeDefinition, HasInterface, HasAddIn or any HierarchicalReference. Dependencies also exist if the Node is the target of a HasSubtype Reference. For Variables and VariableTypes, the value of the DataType Attribute is a dependency. For DataType Nodes, any DataTypes referenced in the DataTypeDefinition Attribute are also dependencies.

For additional details see OPC 10000-5.

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

NodeClass of the target Node.

BrowseName of the target Node.

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.

Conformance Units

Name of ConformanceUnit, one row per ConformanceUnit

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 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 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.

3.4.1.2 Additional References

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

Table 4 – <some> 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.

3.4.1.3 Additional sub-components

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

Table 5 – <some>Type Additional Subcomponents

BrowsePath

Reference

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

3.4.1.4 Additional Attribute values

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.

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