<<< mml
<?xml version="1.0" encoding="UTF-8"?>

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <mo>(</mo> 
    <mfrac linethickness="0">
      <mi>a</mi> 
      <mi>b</mi> 
    </mfrac> 
    <mo>)</mo> 
  </mrow> </math>
>>> native
[ EDelimited
    "("
    ")"
    [ Right (EFraction NormalFrac (EIdentifier "a") (EIdentifier "b"))
    ]
]