Re: combine

>So let's focus on the functionality.  

OK.

>How is adding an additional required
>child element different from adding an additional required attribute (modulo
>the order-dependence issue)?  If you think the latter is OK and useful, why
>isn't the former?  Or perhaps you think it is...

Additing attional required child elements is acceptable to me if 
combine="interleave".  This does not cause the order-dependence.

Cheers,

Makoto