Jim:
        <!-- valid modify vm -->
        <Virtual-Machine type="modify">
                <voename>host.87</voename>
                <memory_size>1024</memory_size>
                <processor_count>1</processor_count>
                <optional_storage>500</optional_storage>
        </Virtual-Machine>

        <!-- valid modify vm -->
        <Virtual-Machine type="modify">
                <voename>host.87</voename>
                <memory_size>NOOP</memory_size>
                <processor_count>2</processor_count>
                <optional_storage>NOOP</optional_storage>
        </Virtual-Machine>

        <!-- invalid modify vm (missing elements)-->
        <Virtual-Machine type="modify">
                <voename>host.87</voename>
                <processor_count>1</processor_count>
        </Virtual-Machine>

current:
modify 1 proc, 1024 mem, 0 optional to 2 procs, 4096 mem, 50 optional
/opt/moab/tools/get.cart.xml.hpoo.pl UID=174
<?xml version="1.0"?>
<environment>
 <action type="modifyvm">
 <!-- modify a vm -->
    <vm>
      <hypervisor>RACE2-HV1</hypervisor>
      <voename>ARMY_NOFP2A_host_704</voename>
      <memory>4096</memory>
      <procs>2</procs>
      <optional>50</optional>
    </vm>
 </action></environment>