n(P(edge-element-presence-none,=,root:http://www.sleepycat.com/2002/dbxml.order),V(edge-attribute-equality-string,order.@id,=,'7')) V(edge-attribute-equality-string,customer.@id,=,'[to be calculated]') V(node-element-equality-string,customer_id,=,'[to be calculated]')