All data in the bottom row of nodes

each upper node holds an entry with the largest and smallest value of the 

	node(s) below it



insert
	search down the tree

	insert into the relevant base node

	if full, split it into two halves

	move back up, updating min and max values, adding entries if the node below 

		it was split, and splitting the current node if full

	if the point is between two base nodes, insert it into the extreme right

		of the left node, or at the extreme left of the right node of

		the two nodes that it's between 





delete

	locate the item

	delete it

	if an empty node, delete upper entries and that node also if empty

	
	or
		tag the item as inactive and rebuild the tree occasionally



keep a linked list along the bottom row to scan from left to right quickly


approx 80 to 100 entries per node


number of read/writes	log(number_of_items)/log(100)



new idea

mm 28/2/2011