DTD interrogations

Hi all,

I'm learning how to read and understand DTD and came up with those interrogations.
ref.: http://www.w3.org/TR/REC-html40/intro/sgmltut.html#h-3.3

According to this statement :
A | B   Either A or B must occur, but not both.

This element declaration :
<!ELEMENT DL    - - (DT|DD)+>

Should read in my perception :
The DL element must contain one or more of either DT or DD elements in any order, but not both.

Instead of the original statement :
The DL element must contain one or more DT or DD elements in any order.

Or I suggest to ajust the "|" operator statement to :
A | B   Either A or B must occur.

What do you think ?



Also, I'd like to know according to this statement :
+(A)    A may occur.

How many time "may it occurs" if it occurs ? One time only ? Or more than one ?

If more than one, what's the difference with the following statement ?
A*  A may occur zero or more times.

And why specify "zero" in the preceding statement ? Isn't it redundant since it "may" occur ?

I suggest changing it to :
A*  A may occur many times.

What do you think ?


Regards,

Jean-Pierre Dubuc