Thanks to all who responded, these are helpful ideas.  I'm pretty new at XML and learning what's "au courant" and what's not is interesting.  What about using attributes to attach syntactic information to the semantic elements? as in:

  <unary-op type="increment" syntax="++" position="(10,25)"/>

-Allen

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What's wrong with something like:

<if-then-else-statement>If <condition>(x&lt;0)</condition><block>

        <unary-op type="increment">++<arg>x</arg></unary-op>;</block>

<block>else

        <unary-op type="increment">--<arg>x</arg></unary-op>;</block></if-then-else-statement>

aside from mixed content not being au courant?

--

Kian-Tat Lim, ktl@k..., UTF-7: +Z5de+pBU-