> A fully-streamed merge, does that mean the processor starts 
> scanning for nodes and stops on encountering the first one 
> satisfying the predicate
> [self::h1 or self::h2] instead of *first* assembling 
> node-sets for both
> h1 and h2, *then* merging them into a union and *then* 
> applying the predicate [1]?

Yes.

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