XML Scheme and elements by rule

[admin]

Hi,
I have following XML:

<ELELEMENTX>
<A/>
<B/>
...
<C/>
<AA/>
...
<XY/>
<ZZ/>
</ELELEMENTX>

The rules are:
1. I always have ELEMENTX.
2. ELEMENTX can have between 1 and 26*26 offspring.
3. Each of these offspring are elements with name of one or two characters (A-Z).

How should the scheme look like?

Thanks.