11. The method of claim 1 , wherein the query qualifiers are vertices of the star-shaped subgraphs, wherein clustering comprises maintaining, for each of the query qualifiers, an indication of whether the corresponding vertex belongs to a star.
11. The method of claim 1 , wherein the query qualifiers are vertices of the star-shaped subgraphs, wherein clustering comprises maintaining, for each of the query qualifiers, an indication of whether the corresponding vertex belongs to a star. 12. The method of claim 11 , wherein clustering further comprises: maintaining, for each of the query qualifiers that belongs to a star, an indication of whether the vertex is a star center, a degree of the vertex, and a list of adjacent vertices.