Enumerationsthat are used as parameters in the Messagesdefined in OPC 10000-4are encoded as xs:stringwith the following syntax:

<symbol>_<value>

The elements of the syntax are described in Table 22.

Table 22– Components of Enumeration

Field

Type

Description

<symbol>

String

The symbolic name for the enumerated value.

<value>

UInt32

The numeric value associated with enumerated value.

For example, the XML schema for the NodeClassenumeration is:

<xs:simpleType name="NodeClass">

<xs:restriction base="xs:string">

<xs:enumeration value="Unspecified_0" />

<xs:enumeration value="Object_1" />

<xs:enumeration value="Variable_2" />

<xs:enumeration value="Method_4" />

<xs:enumeration value="ObjectType_8" />

<xs:enumeration value="VariableType_16" />

<xs:enumeration value="ReferenceType_32" />

<xs:enumeration value="DataType_64" />

<xs:enumeration value="View_128" />

</xs:restriction>

</xs:simpleType>

Enumerationsthat are stored in a Variantare encoded as an Int32value.

For example, any Variablecould have a value with a DataTypeof NodeClass. In this case, the corresponding numeric value is placed in the Variant(e.g. NodeClass Objectwould be stored as a 1).