Should we have a special tag for the "body" of a macro?

I am developing a specification of macroses in XML.

<prog:macro name="f">
   <prog:arguments>
     <prog:argument name="x"/>
     <prog:argument name="y"/>
   </prog:arguments>
   <prog:value name="x"/> then <prog:value name="y"/>
</prog:macro>

or

<prog:macro name="f">
   <prog:arguments>
     <prog:argument name="x"/>
     <prog:argument name="y"/>
   </prog:arguments>
   <prog:body>
     <prog:value name="x"/> then <prog:value name="y"/>
   </prog:body>
</prog:macro>

?

prog:arguments should be optional (as in the case of zero arguments), I 
think.