D(node-metadata-equality-string,name:http://www.sleepycat.com/2002/dbxml,=,'bids.xml',P(edge-element-equality-string,prefix,bid_tuple.itemno))
D(node-metadata-equality-string,name:http://www.sleepycat.com/2002/dbxml,=,'items.xml',U)
V(edge-element-equality-string,item_tuple.itemno,=,'[to be calculated]')
P(edge-element-equality-string,prefix,item_tuple.itemno)