PATCH document models

gistfile1.xml

<!-- 
  simple patch document
  - flat document model
  - always assume //{name} will be sufficient (need not be unique)
  - always treat <value>...</value> as a replacement, even when it includes child elements

  - no guarantees on processing order (adds might execute before delete, etc.)
  - referring to the same name twice in a document is illegal
-->
<patch>
  <add>
    <field>
      <name>...</name>
      <value>....</field>
    </field>
  </add>
  <remove>
    <field>
      <name>...</name>
    </field>
  </remove>
  <modify>
    <field>
      <name>...</name>
      <value>....</value>
    </field>
  </modify>
</patch>