Mapping WSDL Message Parts in Web Service Interaction Activities

In a Web service interaction activity, such as a receive, onMessage, onEvent, invoke, or reply activity, you usually select a WSDL message type variable for the input or output variable. However, if the WSDL operation uses a message containing exactly one part that itself is defined using an element, the Web service interaction activity can use the <fromPart> element for an input variable and a <toPart> element for the output variable. The fromPart or toPart declarations are used in place of the activity's input or output variable declaration.