Shims do_attr node op attr returns the result of functionally applying op to the node's attribute shim to perform operation {*}op on attribute attr of node do_getvals node pattern returns a list of string values of matching attributes shim to return string values of attributes matching pattern of a given node do_ancestors node shim to find node ancestors by repetitive [parent] do_previous* node do_next* node SubQueries subquery return result of new query $query, preserving current node set and and construct the set of nodes present in both $nodes and node set $and or or construct the set of nodes present in $nodes or node set $or not not construct the set of nodes present in $nodes but not node set $not