This adds the children at the XPath specified:

<work xmlns:s="http://apache.org/cocoon/session/1.0">
<s:createcontext name="mystuff"/>
<s:setxml context="mystuff" path="/stuff/">
<child/>
<child/>
<child/>
<child/>
</s:setxml>
<s:getxml context="mystuff" path="/"/>
</work>

At the end, it retrieves the result.