Algorithm 4. KnowledgeInference
Input: User-selected region and knowledge base
Output: Sorted collection of POIs.
1	Fori = 1; i < |L|; i ++ //on each level
2	For j = 1; j < |C|; j ++ //on each cluster on the level
3	If region.contain(C[j])
4	A.add(C[j].authority);
5	SP.add(C[j].poi);
6	Foreach SP do
7	k = KnowledgeKDI(SP);
8	K.add(k);
9	POI = SIoT-inference(SP, A, K);
10	ReturnPOI;