Some .... in .... satisfies

[Istvan]

Hello

Have anybody an idea how to solve "Some ... in ... satisfies " with
standard functions ?


For example this:
"List the reserves of those open auctions where a
certain person issued a bid before another person."


let $auction := doc("auction.xml") return
for $b in $auction/site/open_auctions/open_auction
where
some $pr1 in $b/bidder/personref[@person = "person20"],
$pr2 in $b/bidder/personref[@person = "person51"]
satisfies $pr1 << $pr2
return <history>{$b/reserve/text()}</history>


Thats an query of the XMark Benchmark... Q4.
I need it to execute on Tamino, and so I have to rewrite it, because
Tamino doesn't support
"Some ... in .... satisfies".