rec-declare3

declare test (no visible rendering)

W3C sample	WIRIS
	$f F G$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <declare type="fn" nargs="2" scope="local">
    <ci>f</ci>
    <apply>
      <plus/>
      <ci>F</ci>
      <ci>G</ci>
    </apply>
  </declare>
</math>

Author: MathML 2 Recommendation