Element content in the DTD.

Why isn't the MathML DTD more restrictive in the children allowed in
elements.  For example the msup element requires exactly 2 elements,
however the currect DTD is specified as follows:

<!ENTITY % PresExpression      "(%Presentation; | %ContInPres;)* "     >
<!ELEMENT msup            (%PresExpression;)                      >

It seems to me the would be better written as:

<!ENTITY % PresExpression      "(%Presentation; | %ContInPres;)"     >
<!ELEMENT msup            (%PresExpression;,%PresExpression;)     >

(adjust all other elements apropreately)

Is there drawback that I'm missing?

Russell O'Connor                           roconnor@uwaterloo.ca
"And truth irreversibly destroys the meaning of its own message"
-- Anindita Dutta, "The Paradox of Truth, the Truth of Entropy"