When no alternative datatype is assigned, the WSDL generator and SOAP server will use the default mapping described below:

The REAL SQL type is mapped to the xsd:float SOAP datatype by default and so loss of precision can occur. To improve the precision, the SOAP server will map the xsd:float to the PL double precision datatype instead, but only if the SOAP type is specified. The explicit declaration of __soap_type 'xsd:float' is required to instruct Virtuoso to use the mapping to double precision.

All strings from a SOAP request declared with the SOAP datatype xsd:string will be treated as NVARCHARs on input. All string data such a CHAR, VARCHAR, or NVARCHAR will be encoded as UTF-8 in a SOAP response. This makes processing of wide character sets in SOAP operations possible.

If a User Defined Type (UDT) is used as a type of parameter and no explicit XML Schema datatype given (see special syntax for PL procedures) then in WSDL will be included as a struct definition. Further upon SOAP processing the input struct will be encoded as a UDT instance and passed to the given PL procedure.

The parameters which are declared as an array (see PL procedure syntax) and having no explicit XML Schema datatype given will be exposed as array by means of SOAP encoding rules (see also 'Use' SOAP option to the virtual directory).

Some SOAP applications need a void return as opposed to an empty return, from SOAP operations. To distinguish the empty return from the void return a special SOAP datatype '__VOID__' has been introduced. This will cause the SOAP server to omit the procedure return value when responding to a SOAP request. Also, the return message will be discarded from the WSDL description file.