A simple XMath example

parsed.xml

<Math mode="inline" tex="x_{i+j}" text="x _ (i + j)">
  <XMath>
    <XMApp>
      <XMTok role="SUBSCRIPTOP" scriptpos="post1"/>
      <XMTok font="italic" role="UNKNOWN">x</XMTok>
      <XMApp>
        <XMTok fontsize="70%" meaning="plus" role="ADDOP">+</XMTok>
        <XMTok font="italic" fontsize="70%" role="UNKNOWN">i</XMTok>
        <XMTok font="italic" fontsize="70%" role="UNKNOWN">j</XMTok>
      </XMApp>
    </XMApp>
  </XMath>
</Math>

unparsed.xml

<Math mode="inline" tex="x_{i+j}">
  <XMath>
    <XMTok font="italic" role="UNKNOWN">x</XMTok>
    <XMApp role="POSTSUBSCRIPT" scriptpos="1">
      <XMArg rule="Subscript">
        <XMTok font="italic" fontsize="70%" role="UNKNOWN">i</XMTok>
        <XMTok fontsize="70%" meaning="plus" role="ADDOP">+</XMTok>
        <XMTok font="italic" fontsize="70%" role="UNKNOWN">j</XMTok>
      </XMArg>
    </XMApp>
  </XMath>
</Math>

These are the two XML trees generated for the TeX x_{i+j} in latexml's internal XMath schema: before and after the recdescent grammar parsing stage.