(X)HTML DTD <ul> stricly request <li>

I found this part of XHTML1.1 DTD:

<!ELEMENT ul (li)+>

I thing, it's not usefull to strictly requested <li>, because for 
practical use, you could have this problem.

Some script:
<ul>
    <loop><li>some row</li></loop>
</ul>

There is problem, in fact is many situation, where you have no data and 
you will get this results:

<ul></ul>

I thing it's better to accapt this as correct. I thing, there is no 
problem with this code, element <ul> in practice could be emty, why not?

//Martin Konicek