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