Unclear Part XML 1.1 Specification

Hi all,

>From section 6 of the XML spec, I have learned that:
* binds tighter than |
 + binds tighter than |
but there is no mention of the precedence of the '-' (set difference) operator. At least for me, this makes reading the spec pretty tricky (since I don't know much XML yet). Could someone explain where '-' fits in, perhaps by using the document ::= production, using () to clearly show how '-' works?

Thanks!!
Dan