> I'm not aware of and can't think of any reason 
> why "//" is defined the way it is other than so that //@* 
> will work. Can you think of any?

It's possible that someone thought it would be a really good idea if //p[1]
meant "every paragraph that is the first child of its parent"; but I have no
evidence for this, and if they did, then with hindsight they were probably
wrong.

Michael Kay
http://www.saxonica.com/