The concatenation is accomplished with the core XPath function named concat. In addition, the variable value involved in the concatenation is retrieved with the BPEL XPath function getVariableData. In the following example, getVariableData fetches the value of the name field from the input variable's payload part. The string literal 'Hello ' is then concatenated to the beginning of this value.

<assign>
   <!-- copy from XPath expression to the variable -->
   <copy>
      <from expression="concat('Hello ',
         bpws:getVariableData('input', 'payload', '/p:name'))"/>
      <to variable="output" part="payload" query="/p:result/p:message"/>
   </copy>
</assign>

Other string manipulation functions available in XPath are listed in section 4.2 of the XML Path Language (XPath) Specification.