A Multibranch Search Tree-Based Multi-Keyword Ranked Search Scheme over Encrypted Cloud Data

Algorithm 5

SearchIndex (r, V_Q, k, λ, RL).

	Input:
	The root node of an α-filtering tree, r;
	The query vector of Q, VQ;
	The number of requested documents, k;
	The minimum of the relevance scores between documents in RL and Q, λ;
	The list for storing top-k ranked documents, RL;
	Output:
	RL;
(1)	u = r;
(2)	if u is a leaf node then
(3)	Add all the documents of u·DC in RL;
(4)	if then
(5)	Set the threshold λ equals the minimum of the relevance scores between the candidate documents in RL and VQ;
(6)	Remove the documents from RL, the relevance scores between which and VQ are smaller than λ;
(7)	end if
(8)	else
(9)	if Score (VQ, u·FV)  then
(10)	for each u’ in u·PL do
(11)	SearchIndex (u’, VQ, k, λ, RL);
(12)	end for
(13)	end if
(14)	end if