An example of presentation markup

(X Í Y) ® ((X Ì Y) Ú (X = Y))

  <m:mfenced>
    <m:mi>X</m:mi>
     <m:mo><m:mchar name="SubsetEqual"/></m:mo>
    <m:mi>Y</m:mi>
  </m:mfenced>
  <m:mo color="Blue">→</m:mo>
  <m:mfenced>
    <m:mfenced>
      <m:mi>X</m:mi>
      <m:mo><m:mchar name="subset"></m:mchar></m:mo>
      <m:mi>Y</m:mi>
    </m:mfenced>
    <m:mo><m:mchar name="vee"/></m:mo>
    <m:mfenced>
      <m:mi>X</m:mi>
      <m:mo>=</m:mo>
      <m:mi>Y</m:mi>
    </m:mfenced>
  </m:mfenced>