The AdditionalParametersTypeparameter is used as value of the additionalHeader field of the RequestHeaderand ResponseHeaderparameters. It allows Clientsand Servers to pass additional named parameters with Service requests or responses. These named parameters may be defined by the OPC UA specification, a companion specification or be specific to a vendor implementation. The name is a QualifiedNamewhich allows the same name to be used in different contexts. The value is a Variantwhich allows Structuresto be passed in addition to basic types such as Strings.

Note that the calls to CreateSession/ActivateSessionare made before the Clientcan read the Server’scurrent NamespaceArray. This means that only names with a NamespaceIndexof 0 or 1 may be used in the requests for these Services. Companion specifications and vendors can define names in for use with NamespaceIndex1 if they add prefix that ensures uniqueness. The same restriction applies to values which contain DataTypeswith NamespaceIndexes.

The components of this structure are defined in Table 112.

Table 112– AdditionalParametersType






Specifies a list of value qualified by a name.


KeyValuePair []

A list of headers identified by a QualifiedName.

The KeyValuePairtype is defined in OPC 10000-5.