MathML 4 question

Should the parentheses in the following stretch to fit their contents?

<math>
            <mi>a</mi>
            <mo>(</mo>
            <mi>b</mi>
            <mo>+</mo>
            <mi>c</mi>
            <mo>)</mo>
</math>

The implied <mrow> contains a leading <mi>. Also should the parenthesis in the following stretch?

<math>
            <mi>a</mi>
            <mo>(</mo>
            <mi>b</mi>
            <mo>+</mo>
</math>

For OfficeMath, we convert delimiter expressions to an equivalent of <mfenced> internally and I’m working on emulating <mfrenced> with <mrow> infix notation.

Thanks,
Murray