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


The elements of the syntax are described in Table 22.

Table 22– Components of Enumeration






The symbolic name for the enumerated value.



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" />



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).