Xref returns the cross reference index of the node. Tag returns the tag of the node. If there is no value, value returns null. Whenever there is no such related node, these functions return null.
Parent returns the parent node of the node, if any.
Child returns the first child node of the node, if any. Sibling returns the next sibling node of the node, if any. Savenode makes a copy of the node, and the structure of nodes below it. Its first argument is a node expression, and its second parameter is a variable that iterates through each direct child node of the first node.