[Retracted] A Two-Phase Method for Optimization of the SPARQL Query

Algorithm 1

Two-phase algorithm for SPARQL query processing.

Input:SPARQL queries, queryStr, Trie;

Output:combined Results;

1 Parse queryStr;

2 Block queryStr into n blocks;

3 Fori ←0 to n-1

4  Filter out joins with (?s, p, o) by getVariableSelectivity(queryStr.variable[i]) in order;

5 endFor

6 For each variable v Variables

7  filterList ← getVertexList(Trie,v);

8  Merge results using filterList; // By using Trie, useless vertices are filtered by the longest predicate path index of each variable and then the results will be combined.

9 endFor

10 Output Results;