Best Way to store Data in XML DOC

I am looking for an Idea how to best store following data in XML so it can be easily read.
Background, i have an app which has api and each api has functions and the functions require parameters and values when they are called. So i am trying to build a test client who has the following hierarchy

<api>
  <function>
      <parm><value><required>
      <parm><value><required>
  </function>
<function>
      <parm><value><required>
      <parm><value><required>
  </function>
</api>
<api>
  <function>
      <parm><value><required>
      <parm><value><required>
  </function>
<function>
      <parm><value><required>
      <parm><value><required>
  </function>
</api>

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