How do I reflect a "void" return type in the WSDL?

I'm writing a function (operation) that takes a single integer parameter, performs some task but does not return any value (I would think this is different from returning a value of xs:anyType). What parameter do I need to set in the JavaScript file to achieve this?

<types>
    <schema>
        <element name="myMethod">
            <complexType>
                <sequence>
                    <element name="myParam" type="xsd:integer"/>
                </sequence>
            </complexType>
        </element>
        <element name="myMethodResponse">
            <complexType/>
        </element>
    </schema>
</types>

I can do it for the input parameter using

myMethod.inputTypes = { "myParam" : "xs:integer" };

But I'm not sure how to do it for the output parameter.

On a related note, I heard from someone that Axis2 does not allow one to define void operations. You have to return some value. Is this true?