Use Assign to build whole message at once (all parts)

Let's say you have WSDL parts defined as follow:

<wsdl:message name="HelloMessage">
  <wsdl:part name="part1" type="xsd:string"/>
  <wsdl:part name="part2" type="xsd:string"/>
</wsdl:message>

In order to build whole message at once, you need to use following statement:

<assign>
  <copy>
    <from><literal><message xmlns=""><part1>abc1</part1><part2>abc2</part2></message></literal></from>
    <to>$myVar</to>
  </copy>
</assign>

Complete BPEL example is provided here: TestMultiPartMessage